Glossary of Automotive Terms – T

Letter T – Dictionary of Automotive Terms

A letter rating for tires to indicate that they are theoretically rated for speeds up to 190 km/h (118 mph), as in P220TR15.The next higher rating is H and the one lower rating is S
Abbreviation for Temperature Air (Honda)
  1. A small projecting part as on a tab washer, or on a gasket where it engages with another seal.
  2. Not a continuous flange as provided at the top mounting of a fender, but a short flange section to provide localized fitting of one panel to another
Abbreviation for Thermactor Air bypass solenoid
Tab washer
A washer with a projection that may be hammered against a flat side of a nut, or into a hole in the surface, or over an edge, in order to secure the nut to the surface on which it bears
  1. Abbreviation for Thermostatic air cleaner
  2. Abbreviation for Throttle Actuator Control
Abbreviation for Tachometer.
Colloquial term for Tachograph
Instrument to record, on a graph, vehicle trip information such as speed, rpm, distance, time traveled, stop and go periods. It is used on transport trucks.

  1. A device used to indicate the speed of the engine in rpm. The tachometer is mounted on or near the dashboard (some even appear on the hood and others in a heads-up display on the windshield). It helps the driver to know the optimum rpm for changing gears on a vehicle with manual transmission. A tachometer is also a diagnostic device which a mechanic uses to determine Idle speed and other carburetor and running settings. Also called a rev counter
  2. A small generator normally used as a velocity-sensing device. Tachometers are typically attached to the output shaft of DC servo motors requiring close speed regulation. The tachometer feeds its signal to a control which adjusts its output to the DC motor accordingly (called closed loop feedback control)
  1. A term used to describe the sticky quality of a rubber compound.
  2. The sticky quality of an adhesive film, either while wet or after the film has set. Technically it is the pull resistance (measured in dynes) exerted by a material completely adhering to two surfaces being pulled apart.
Tack cloth
A special cloth used to wipe sanded panels prior to spraying in order to remove even minute dust particles and other foreign substances from the panel surface
Tack coat
The first Coat of Enamel that is allowed to dry until tacky usually about 10-30 minutes, depending on the amount of Thinner used. The surface is tacky when it will not stick to the finger when light pressure is applied.
Tack hammer
A special hammer with a magnetic head for inserting small nails or tacks
The stickiness of the adhesive film while in the stage of drying.
Attaching a panel provisionally by placing a few spots of weld along its outline; final spot or seam welding is carried out only afterwards
Tack rag
A cloth impregnated with a non-drying Varnish that is used to pick up dust and dirt particles.
Tack range
The time during of a film to distortion or rupture when it is exposed to forces exerted in opposite directions (measured in psi).
Tack strip
Tack weld
Small weld used to temporarily hold together components of an assembly.
Tack welding
Attaching a panel provisionally by placing a few spots of weld along its outline; final spot or seam welding is carried out only afterwards
To bend a wheel over on itself, in the shape of a taco. ‘I taco’d my wheel when I hit that tree.’
TAC system
A contact breaker ignition system developed by Lucas, controlled by two transistors, one serving as a power output transistor
Tactile paving
Contoured paving to mark out pedestrian crossing points for those with vision problems.
Abbreviation for Thermactor air diverter solenoid
Tadpole cycle
A three wheel cycle with two wheels in front and one in the back.

Abbreviation for Tertiary amyl ethyl ether
Tag axle
A non-powered axle placed behind the drive axle in large trucks. Contrasted with a Pusher axle which is placed in front of the drive axle.
Tag block
A wiring harness terminal block with a number of electrical plugs and sockets
Tag-Robinson Colorimeter
An instrument used to determine the color of oils. Also a scale of color values.
Tag Trailers
A single axle trailer with equipment like generators, cement mixers, or wood chippers.
Tagalong Trailers
Usually single axle equipment like generators, cement mixers, or wood chippers.
TahoeClick image for books on

A model of SUV produced by the Chevrolet division of General Motors from 1995 to 2008

The rear of a vehicle.

A board at the rear of a pick-up that can be removed or let down on a hinge. Compare Tailgate
Tail fin
A vertical fin on the back of the rear fenders. Copied from a Lockheed P38 fighter plane, Cadillac introduced tail fins on a coupe in 1948; they were a fashion until the 1960s
  1. On a truck it is the fold down access door to the truck bed. On some station wagon and SUVs, it is the rear opening which usually requires the window to be lowered before the tailgate folds out. It differs from a liftgate in that the back opening is raised to allow entry.
  2. As a verb, to follow closely behind another vehicle–an illegal and unsafe procedure.
Driving so close to the vehicle in front as to be affected by its slipstream; a very dangerous practice as available reaction time is reduced to a minimum. The correct distance is 2 or 3 seconds behind the vehicle in front.
Tail heavy
The description of the towing vehicle if the vehicle being towed is too heavy
Tail lamp
The red rear light that illuminates as soon as the lights are switched on, to show your vehicle to those behind you
Tail lift
Tail light
The red rear light that illuminates as soon as the lights are switched on, to show your vehicle to those behind you
Tail light box
A deep-drawn panel spot-welded into the tail light aperture to accept the complete tail light cluster. The tail light box provides better corrosion protection for the electrical connections of the tail light than would be possible by installing the tail light with a rubber seal into the open light aperture
Tail light panel
Tail light surround
Tail pipe
  1. The exhaust pipe which runs from the muffler to the rear of the vehicle and is open to the atmosphere, through which the exhaust gases are routed into the atmosphere.
  2. Outlet pipe from the evaporator.
The last link in the exhaust system. Conducts exhaust gases from the muffler to the rear of the car and into the atmosphere.
Tailpipe expander
A special automotive tool used for reshaping and expanding tailpipes evenly, to assure a tight fit and prevent exhaust leaks
A ship’s propeller shaft.

Take foot off the accelerator
The action of Easing up on the accelerator completely so that there is only a minimal amount of fuel entering the engine thus the engine will slow down
Take foot off the gas pedal
The action of Easing up on the gas pedal completely so that there is only a minimal amount of fuel entering the engine thus the engine will slow down
Take foot off the throttle pedal
The action of Easing up on the throttle pedal completely so that there is only a minimal amount of fuel entering the engine thus the engine will slow down
Take off
Take up
To begin to transmit the drive when the clutch is engaged
The act of taking up.

Take-up point
Take-up valve
A vehicle brand of which all 105C and 110C models are classic cars. The 1946-54 Lago 4.5 models are milestone cars.
Talbot Lago
A vehicle brand of which the following are classic cars:

  • 1930-35 8-cylinder
  • 1936-39 4 Litre 6-cylinder
  • 1946-48 4 1/2 Litre
Powder lubricant to prevent sticking between tube and tire. A soft mineral; a basic magnesium silicate usually occurring in foliated, granular, or fibrous masses, used in the manufacture of electrical insulators
Talking warning system
Using the car radio speakers, this microprocessor-based system tells the driver the source of the problem in a clear, pleasant (female) voice. If the radio is on at the time of the alert, the computer automatically turns down the volume so the warning can be heard
Tall oil
The oily mixture of rosin acids, fatty acids, and other materials obtained by acid treatment of the alkaline liquors from the digesting (pulping) of pine wood.
Abbreviation for Tertiary amyl methyl ether
Tampering detector
Tamperproof carburetor
A carburetor with factory-adjusted idle speed, sealed idle speed adjustment screw, and provisions to ensure that exhaust emission levels remain within specified limits over an extended period of time
  1. A bicycle that provides seats, bars, and pedals for two or more riders, one behind the other.
  2. A tractor-trailer truck.
Tandem axle
Tandem axles
  1. A pair of axles at the rear of the power unit (tractor or straight truck) or trailer. For power units, if described as a tandem, usually indicates the number of drive axles on the power unit.
  2. A combination of two axles having a common suspension. Pair of axles and associated suspension usually located close together. Called Tandems.
Tandem booster
A vacuum power booster that uses two diaphragms to increase brake application force. Smaller in diameter than single-diaphragm boosters.
Tandem bus
A colloquial term for an articulated bus
Tandem drive
Two powered axles in combination.
Tandem master cylinder
  1. A master cylinder with two pistons; when the brake pedal is pressed, the pushrod activates the primary piston which in turn moves the secondary piston; necessary for dual-circuit braking systems
  2. A master cylinder having a single bore with two pistons and separate fluid compression chambers. In the event of significant fluid loss in one circuit, this design, used in split braking systems, ensures that there will be some braking power in the other circuit. For this reason, it has been mandatory on cars marketed in the US since 1967
A device mounted on a rotating shaft or component that engages in a recess of a component to be driven

Tangential-flow scavenging
A container into which any liquid or gas can be held. Also it may even be empty such as a Vacuum tank.

Tank bag
A bag that sits on the gas tank of the motorcycle, secured by a magnet or by straps. Tank bags are good for holding lightweight items such as gloves, maps, and wallets
A river barge for the carrying of liquid bulk cargo
Tank bib
A leather or vinyl covering over the gas tank of a motorcycle to protect the finish from scratches
Tank chap
A leather or vinyl covering over the sides of a gas tank of a motorcycle to protect the finish from scratches
  1. An enclosed cargo body designed solely for the transportation of fluid or gaseous commodities in bulk. Not to be confused with trailers which are designed for carrying dry bulk products.
  2. A ship designed for transporting liquid cargo, usually petroleum products.
  3. A dry bulk tanker. Sometimes called air-can trailers. Used exclusively for hauling dry bulk material. Cargo is emptied pneumatically.
Tanker truck
A truck designed to carry liquid in bulk. British term is petrol tanker
Tank sender
Tank, supply
Separate tank connected directly or by a pump to the oil-burning appliance.
A covering usually of wood, placed over the tank top for its protection
Tank Vapor Valve
Tank Wagon Sales

  1. To cut threads in a hole, nut, or tube with a rotating tool called a ‘tap.’
  2. The fluted tool used to cut the threads.
  3. To strike lightly
Abbreviation for Transmission Adaptive Pressure
Tap and die set
A set of taps and dies for internal and external threading, usually covers a range of the most popular sizes.
Tap Bolt
A fully threaded hexagon head bolt.
Tap-changing Equipment
Tap End Stud
A double-end stud having each end threaded for a different class of fit. The tap end has a Class 5 fit to produce an interference fit in a tapped hole for semi-permanent assembly. The nut end is threaded Class 2A for assembly with a standard nut.
  1. A gradual narrowing in size of a long round object toward one end.
  2. A lack of parallelism. A defect in which the thickness of the drum or rotor at the outer edge differs from its thickness at the inner edge.
Taper-breaking tool
Taper cutter
A tool used to ream, deburr, align, and enlarge holes, e.g., on car bodies. Also called Tapered reamer
Tapered Bottom Bracket
Tapered compression ring
The upper compression ring which, due to its tapered cross-section, requires a reduced running-in period thus ensuring a tight seal quickly
Tapered leaf spring
Tapered punch
Tapered reamer
Tapered roller bearing
Tapered roller bearingTapered roller bearing

An antifriction bearing using a series of tapered, cone-shaped hardened steel rollers operating between an outer and inner hardened steel Race. It can accept axial thrust as well as providing shaft location. Used where both radial and thrust loads are to be handled.

Taper leaf spring
Taper of Head
In flat bearing surface fasteners, the taper of a head or nut is the angle between a side and the axis.
Taper pin
Taper pinTaper pin

A roll pin or Dowel pin that is wider at one end than the other. The taper pin aids in hole alignment.

Taper seat
  1. A conical seat that provides positive centering of a wheel bolt head in the wheel. The opposite of Radius seat.
  2. A seal without a gasket achieved by mating the conical surface of the spark plug shell and the cylinder head
Tape weight
Tap holder
A tool used to hold and drive taps, reamers, and screw extractors with two long handles to provide high leverage for turning operation
Tapped Hole
A threaded hole in a part.
  1. The screw used to adjust the Clearance between the Valve stem and the Lifter or the Rocker arm.
  2. TappetTappet

    The Valve lifter itself.

Tappet adjusting screw
Tappet gasket
Tappet noise
Noise caused by the Lash or Clearance between the Valve stem and Rocker arm or between the valve stem and Valve lifter.
Tappet wrench
A wrench designed for adjusting valve clearances on OHV-engines with bucket tappet assembly that use an adjusting screw instead of valve shims for adjustment
Tapping plate
Tapping Screw
A screw which is threaded to the head and designed to form or tap its mating thread in one or more of the parts to be assembled, of various types as follows:

  • Tapping Screw, Type A: A thread-forming type of tapping screw having a gimlet point and a thread of relatively coarse pitch and special form, used in punched, or nested holes in metal sheets or in treated plywood or special asbestos compositions.
  • Tapping Screw, Type B: Also designate ‘type Z.’ A thread-forming type of tapping screw, having a blunt point with tapered threads of moderate pitch, used with punched, drilled or nested holes.
  • Tapping Screw, Type C: A thread-forming type of tapping screw having a blunt point with tapered threads at the end, having UNC or UNF threads and designed for fastening metal sheets.
  • Tapping Screw, Type D: Also designated ‘type EC.’ A thread-cutting type of tapping screw having the same thread as type C but provided with a fluted end produced at thread rolling or a milled slot (or slots) produced after thread rolling.
  • Tapping Screw, Type F: A thread-cutting type of tapping screw having the same thread form as type C but provided with a multiple flute tapered end to facilitate tapping.
  • Tapping Screw, Type FZ: A thread-cutting type of tapping screw having the same thread form as type B but provided with a multiple fluted tapered end to facilitate tapping.
  • Tapping Screw, Type G: Also designated ‘type EC.’ A thread-cutting type of tapping screw having the same thread form as type C but provided with a slot across the end to facilitate tapping in hard materials or deep holes.
  • Tapping Screw, Type H: Also designated ‘type DB’ or ‘type 25.’ A tapping screw having the same thread as a type B but provided with a slot in the end to facilitate tapping in plastics.
Tap ratchet
A tool with ratchet mechanism used to hold and operate bits such as taps, drills, reamers, or screw extractors
Tap spanner
Tap wrench
A black, sticky substance made from petroleum. It is useful for patching cracks in the road. However, when driving over it, the wheels kick up particles of it on a vehicle’s painted surface.

Tare weight
The weight of a truck, exclusive of its contents, but including gas, oil, etc., ready to roil.

A removable-roof body style popularized by Porsche that is similar to a convertible except that it incorporates a fixed, roll-bar-like structure running from side to side behind the front seats.
Targa bar
A type of roll bar made of a relatively wide band of sheet steel rather than of tubing; made popular by the Porsche 911 Targa
Targa top
A rigid, removable roof section between the windshield and Targa bar
  1. A duty or tax imposed on imports.
  2. A published volume of rate schedules and general terms and conditions under which a product or service will be supplied.
Tariffs and Trade
To discolor due to the formation of a thin film of oxide, sulfide, or some other corrosion product
Waterproof canvas material used to cover cargo being transported
Tar remover
Tar sands
Naturally occurring bitumen-impregnated sands that yield mixtures of liquid hydrocarbon and that require further processing other than mechanical blending before becoming finished petroleum products.
Abbreviation for Throttle Adjust Screw
Abbreviation for Thermal-Aerodynamic Systems Engineering
TA sensor
Intake Air Temperature Sensor
A vehicle brand of which the 1925-1948 models with required application are classic cars.
Ford TaurusClick image for books on
Ford Taurus

A model of automobile manufactured by Ford

Abbreviation for Temperature Actuated Vacuum
Tax disc
A road fund license disc displayed on the windshield to show that a British road tax has been paid
A vehicle in which passengers are carried for hire which is usually recorded by a meter

A car in which passengers are carried for hire which is usually recorded by a meter
Taxi rank
A British term for a Taxi stand
Taxi stand
A place where taxis wait to be hired
Abbreviation for Towbar
Abbreviation for Tertiary butyl alcohol
A rod which is inserted into the holes of a Box spanner. The British term is Tommy bar.

T bar roof
A roof with a T-shaped bar connecting the windshield and the rear section of the roof
Abbreviation for Throttle body injection
Abbreviation for Total Base Number. ASTM D2896. Measured in mg. The TBN of KOH is the amount or ability of the product needed to neutralize an acidic solution through reverse titration. In a motor oil, this is a property which allows the oil to neutralize acids from combustion that would otherwise degrade the oil.
T Bone
  1. Model-T Ford car.
  2. The act of one vehicle hitting another against its side. The expression comes from the shape of a T-bone steak which in turn looks like the letter ‘T’
Model-T Ford car.
A description of a vehicle that has been hit on its side.
  1. Abbreviation for Torque converter
  2. Abbreviation for Twin carburetors
  3. Abbreviation for turbocharger
Abbreviation for Thermostat Controlled Air Cleaner
Abbreviation for Torque Converter Clutch Locks up Torque Converter to output shaft to provide direct drive to wheels
Abbreviation for Torque Converter Clutch Pressure
Abbreviation for Toyota Computer Controlled System
Abbreviation for Transistorized coil ignition
Abbreviation for Transistorized coil ignition with hall sensor
Abbreviation for Transmission Control Indicator Lamp
  1. Abbreviation for Transmission control module
  2. Abbreviation for transportation control measure
Any connector in the shape of the letter T — often referring to a hollow unit. For example, the line coming from the Windshield washer pump is connected to the bottom part of a T and the crossbar at the top sends the fluid to the two nozzles (one on each side of the windshield). It differs from a Y-connector in that the crossbar is straight across while the Y-connector has a V-shape crossbar.
  1. Abbreviation for Temperature Compensated Accelerator Pump
  2. Abbreviation for Torque Charger
  3. Abbreviation for Traffic Control Plan
  1. Abbreviation for Transmission controlled spark (GM)
  2. Abbreviation for Transmission Control Switch
  3. Abbreviation for Traction Control Switch
TC spark plug
Abbreviation for thermocouple spark plug
A proprietary rubbing compound used to give a finish to dull paintwork
Abbreviation for Turbo Diesel
Abbreviation for Top dead center.
Abbreviation for top dead center sensor. A backup sensor for the ECU should the crank/cylinder sensor fail
  1. Abbreviation for Turbo diesel engine with direct injection
  2. Abbreviation for Turbo Direct Injection
TD rim
A wheel rim which incorporates two grooves running around the circumference of the bead seats; the tires have special extended bead toes which fit into these grooves
TD wheel
A safety wheel incorporating a Td rim with run-flat properties, which in case of a puncture allow further driving of up to 20 miles at a maximum speed of 40 mph. In the event of deflation, the reinforced bead toes are held firmly in place by the grooves, thereby preventing the tire from sliding into the rim well. The width and diameter of both tire and rim are given in millimetres, to prevent the fitting of a normal tire to a TD rim or conversely of a TD tire to a conventional wheel. Rim marking 150 TD 365 stands for a rim measuring 150 mm in width and 365 mm in diameter and having a TD contour
  1. Abbreviation for Totally enclosed electric motor housing
  2. Abbreviation for Thermal Expansion
A pair of drivers who alternative driving and resting.

Tear it down
Tear seam
Abbreviation for Thermactor exhaust control system
A section of bicycle trail that is difficult to ride because of rocks, tree roots, steep drops, or stunts.
Technical Education Foundation
Abbreviation for Totally enclosed fan-cooled enclosure
A registered trademark of DuPont for its fluorinated resins and coating applications including but not limited to fluoropolymers, fluorochemicals, films, surface and fabric protectors. It provides excellent self-lubricating (slippery) bearing properties.

Abbreviation for Tetraethyl lead
Abbreviation for Telescoping steering wheel.
Telelever system
The most successful alternate front suspension, made by BMW, which takes the shock-absorption function of a hydraulic fork and transfers it o a shock absorber located behind the steering head.
Telescopic forks
Front motorcycle suspension system with two fork legs, each with sliding and fixed tubular members that telescope together to allow suspension movement
Telescopic shock absorber
A tubular spring damper operated by rod and piston; the most common type of shock absorber
Telescopic steering column
A steering column that collapses in on itself on impact
Telescoping steering wheel
(tele) A Steering column which can be shortened or lengthened to provide the most comfortable driving position.
Tempa spare
A spare wheel type with considerably reduced overall dimensions (rim width 3.5-4.0 in), designed to operate at a higher inflation pressure than the standard tire and wheel unit
Tempa spare wheel
A spare wheel type with considerably reduced overall dimensions (rim width 3.5-4.0 in), designed to operate at a higher inflation pressure than the standard tire and wheel unit
  1. To effect a change in the physical structure of a piece of steel through the use of heat and cold.
  2. A thermal treatment of finished products (metals, alloys, plastics) to remove internal stresses
  3. To heat material after hardening to a temperature of perhaps 540°C and allow to cool naturally in order to soften material and make it less brittle. Or to heat to a lower temperature of possibly 260°C to relieve stress in metal without affecting the hardness.
  1. Degree of hotness or coldness as measured by a thermometer.
  2. Measurement of speed of motion of molecules.
  3. The measure of heat intensity or concentration, expressed in degrees. Measured by a thermometer. Temperature is not a measure of heat quantity but of heat quality.
Temperature activity
Temperature Coefficient
The amount that the voltage, current, and/or power output of a solar photvoltaic cell changes due to a change in the cell temperature.

Temperature Coefficient Thermistor
Temperature Collectors
Temperature compensator
In some SU carburetors, a wax-type thermostat contained in a housing at the base of the jet head; with increasing temperature, the wax expands and pushes the jet upwards, thereby reducing the effective area of the jet and restoring the correct fuel flow. As underhood temperature increases, fuel viscosity is reduced, resulting in increased fuel flow through the carburetor jet and an air/fuel mixture which is too rich; as this causes excessive emissions, particularly during idling, some SU carburetors feature a capstat temperature compensated jet
Temperature control
Temperature-operated thermostatic device which automatically opens or closes a circuit.

Temperature control element
A temperature-controlled valve spring bias regulator in an oil filter bypass valve which controls the bypass valve as a function of oil temperature
Temperature dial
A calibrated control lever or wheel used to regulate automatic temperature control system modes.
Temperature fouling
Temperature gage
Temperature gauge
An instrument for measure the temperature of the coolant in engine block.

Temperature-humidity index
  1. A number representing an estimate of the effect of temperature and moisture on humans, computed by multiplying the sum of dry-bulb and wet-bulb temperature readings by 0.4 and adding 15, with 65 assumed as the highest comfortable index.
  2. Actual temperature and humidity of air sample compared to air at standard conditions.
Temperature-measuring spark plug
Temperature of deflection under load
The ability of a test specimen to preserve its shape up to a given temperature under a given dead load; characterized by the temperature at which the specimen supported at both ends and heated continually and uniformly in a liquid heat-transfer medium is deformed by a given amount when the load is applied midway between the supports
Temperature phosphating
Temperature Regulator Valve
Temperature relief valve
A valve which automatically opens and closes a relief vent, depending on whether the temperature is above or below a predetermined value.
Temperature rise
The amount by which an electric motor, operating under rated conditions, is hotter than its surrounding ambient temperature
Temperature sensing bulb
Bulb containing a volatile fluid and bellows or diaphragm. Temperature increase on the bulb causes the bellows or diaphragm to expand.
Temperature-sensitive bimetal coil
A part made of dissimilar metals that cause the coil to flex with changes in temperature. The flexing bipetal can operate a temperature-sensitive device, such as a carburetor choke, or the hydraulic circuit in most non-electric radiator fans
Temperature sensor
Temperature switch
Temperature vacuum switch
(TVS) controls vacuum to the EGR valve and/or canister purge valve based on coolant or intake air temperature. Canister purge and EGR do not typically operate when the engine is cold
Temperature valve
Temperature vulcanizing
Temperature vulcanizing sealer
Tempered glass
Reheating a quench-hardened or normalized ferrous alloy to a temperature below the transformation range and then cooling at any rate desired.
Temper rolling
Rolling for the purpose of removing spangles on hot-dip galvanized steel sheet
TempestClick image for books on

A mid-size car manufactured by the Pontiac division of General motors from 1961 to 1972 and 1988 to 1991

A pre-cut pattern, usually metal, used to determine the contour of a buffed tire.

Ford TempoClick image for books on
Ford Tempo

A model of automobile manufactured by Ford

Temporarily discharged fuel
Fuel that was irradiated in the previous fuel cycle (cycle N) and not in the following fuel cycle (cycle N+1) and that will be irradiated in a subsequent fuel cycle.
Temporary spare wheel
A tender ship is one which have a long period of roll but may list excessively in a strong wind and may be dangerous if a hold is flooded following a collision
Tensile force
The stretching force that acts on the windshield header to keep the convertible top tight
Tensile strength
  1. Regarding a tire, it is a measurement of the greatest longitudinal stress a tire cord can bear without breaking.
  2. Maximum pull stress in psi a specimen is capable of developing.
  3. The resistance which an adhesive film remains tacky.
  4. A common measure to compare the strength of a fastener. It is the load needed to pull the fastener apart.
  1. A pulling or stretching stress applied to an object.
  2. Voltage.
A device designed to maintain the tension of a belt or chain.

Tensioning spring
A spring designed to maintain tension in a drum brake
Tension lead
Abbreviation for Totally enclosed non-ventilated electric motor housing.

TercelClick image for books on

A model of automobile manufactured by Toyota

  1. A connecting point in an electric circuit.
  2. When referring to the battery, it would indicate the two battery posts.
Terminal block
A plastic or resin assembly containing two rows of terminals screws. Used to join the circuits in several wiring harnesses
Terminal post
Terminal reamer
A tapered reamer-type tool used to remove corrosion from the inside of battery cable clamps
Terminal Stud
A threaded and collared pin having a plain cylindrical section, used as a contact terminal on electrical appliances. Some types are headed instead of collared
Terminal tower
The terminals at the top of the distributor cap into which the spark plug wires fit. Also called distributor tower
Terminal voltage
The sum of the individual battery cell voltages
Term interest rate
Terrain bike
Terrain tire
Terrain vehicle
A model of automobile manufactured by Buick Division of General Motors from 2005-07
Tertiary Amyl Ethyl Ether
(TAEE) An ether based on reactive C5 Olefins and ethanol.
Tertiary Amyl Methyl Ether
(TAME) (CH3)2(C2H5)COCH3 An ether based on reactive C5 Olefins and methanol. An oxygenate blend stock formed by the catalytic etherification of isoamylene with methanol.
Tertiary butyl alcohol
(CH3)3COH: An alcohol primarily used as a chemical feedstock or a solvent or feedstock, for isobutylene production for MTBE (methyl tertiary butyl ether) and produced as a co-product of Propylene oxide production or by direct hydration of isobutylene.
Tertiary Butyl Ether
A series of procedures to determine if a component meets a specified standard

TestarosaClick image for books on

A model of automobile manufactured by Ferrari

Test bar
A test specimen with the shape of a bar as used in the impact resistance test
An area equipped with instruments, used for testing machinery, engines, etc., under working conditions
Test current for low temperatures
The specification for assessing battery starting behavior at low temperatures and under given conditions; indicated in amps on the battery case
Test cycle
Test drive
A trial drive of a car after it has been repaired, or of a new car to decide if one likes it enough to buy it
To take a car for a test drive before purchasing it
Test dummy
Test equipment
Test head
The head or height of a column of water which will give a prescribed pressure on the vertical or horizontal sides of a compartment or tank in order to test its tightness, or strength
Testing Materials
Testing Unit
Test lamp
An automotive tool used to test powered circuits on 6-24 volt systems such as headlights, horns, signal, or tail lights. It consists of a handle with a bulb and sharp probe and a lead with a crocodile clip, The sharp probe is used to pierce the insulation on the wire leading to the defective part; if the bulb glows, the circuit is complete. Simpler designs do not feature a probe, but come in a standard screwdriver shape
Test light
  1. An automotive tool used to test powered circuits on 6-24 volt systems such as headlights, horns, signal, or tail lights. It consists of a handle with a bulb and sharp probe and a lead with a crocodile clip, The sharp probe is used to pierce the insulation on the wire leading to the defective part; if the bulb glows, the circuit is complete. Simpler designs do not feature a probe, but come in a standard screwdriver shape
  2. Light provided with test leads. Used to test or probe electrical circuits to determine if they have electricity.
Test method
Test Modes
Test pilot
A person who responds to advertisements, takes the vehicle for a ride, but really has no intention of purchasing the vehicle. He is related to a tire kicker. The difference is that a tire kicker wastes the seller’s time examining the vehicle while a test pilot wants to experience the ride.
Test port
The Schrader valve fitting located on the fuel rail of a port injection system used for relieving fuel pressure and for hooking up a fuel pressure gauge
Test Procedure
Test vehicles
Vehicles operated by a motor vehicle dealer solely for the purpose of promoting motor vehicle sales or permitting potential purchasers to drive the vehicle for pre-purchase or pre-lease evaluation; or a vehicle that is owned and operated by a motor vehicle manufacturer or motor vehicle component manufacturer, or owned or held by a university research department, independent testing laboratory, or other such evaluation facility, solely for the purpose of evaluating the performance of such vehicles for engineering, research and development, or quality control reasons. Also called Demonstration vehicle
Tether kill switch
A safety device used on snowmobiles and personal watercraft. One end is attached to the operator’s wrist and the other end is plugged into a special switch. When the operator falls off his vehicle, the tether pulls out of the switch causing the engine to die.
Tetraethyl lead
(TEL) a lead Compound used as an Additive to increase the octane rating and reduce the Knock or Detonation tendencies of gasoline. One gram of lead increases the octane of one gallon of gasoline about 6 numbers. The EPA has phased down the use of lead in gasoline as it has been determined to be a health hazard. Lead has been prohibited in highway vehicle gasoline since January 1, 1996.

Tetramethyl lead
(TML) An anti-knock fuel additive
Abbreviation for Twenty Foot Equivalent Unit for measuring container capacity on ships, railcars, etc.

Texas gate
A series of pipes spaced about 3 or 4 inches apart placed across the road to discourage animals from entering or leaving a particular area. Besides creating a visual barrier to animals, the wires between the round, metal bars that form the texas gate are electrified to further discourage bears from trying to walk over the gate. The electric texas gate is designed to allow vehicles to safely pass over it, but is not intended for pedestrians or cyclists. People on foot or bike must use the pedestrian gate at the side of the texas gate. Do not walk or bike over the texas gate. Also called cattle guard.
Abbreviation for Thick film integrated
T Ford
Model-T Ford car.
Model-T Ford car.
  1. Abbreviation for Throttle Fluid Pressure
  2. Abbreviation for Transmission Fluid Pressure
Abbreviation for Thin Film Technology.



T-handle shifter
A shift lever (usually found on automatic transmissions) mounted on the console and shaped like the letter T
T-handle socket
A tool in which a socket has been welded to a long rod (about 8 to 10 inches). At the other end of the rod, a crossbar has been welded. Thus it is formed in the shape of the letter T. In some instances it speeds up the removal and installation of bolts.
Abbreviation for Total hydrocarbons
T head
  1. A type of cylinder head in a side valve engine where the valves are either adjacent and parallel or installed on opposite sides of the piston in a configuration resembling a T.
  2. A type of screw or bolt head shaped like a T.
T-Head Bolt
tboltT-head bolt

Bolt with a head that slightly curves in the shape of the letter ‘T’

T head engine
T-head engine
An engine in which the arrangement of the valves on either side of the combustion chamber creates a T configuration. Usually the intake valves are on one side and the exhaust on the other. The modern crossflow cylinder heads are variations on this old concept. But the original design is not in current use.
Theft protection
Theft system
Theory Of Magnetization
Theory Of Solids
Quantity of heat equal to 100,000 Btu.
GM’s thermostatically controlled air cleaner system
An air injector type of exhaust emission control system used on Ford vehicles.

Thermactor II
Also called Ford’s Pulse air system
Thermactor air bypass solenoid
(TAB) an electrical solenoid that switch engine manifold vacuum to bypass the atmosphere
Thermactor air control valve
Combines a bypass (dump) valve with a diverter (up/down stream) valve; controls the flow of the thermactor air in respond to vacuum signals to its diaphragms
Thermactor air control solenoid vacuum valve assembly
Used on thermactor air control systems; consists of two normally open solenoid valves with vents
Thermactor air diverter solenoid
(TAD) and electrical solenoid that switches engine manifold vacuum; when energized, switches Thermactor air from downstream (past the oxygen sensor) to upstream (before the oxygen sensor)
Thermactor exhaust control system
(TEC) an air injector type of exhaust emission control system used by Ford
Therma Fleece
A type of very soft fabric used in a garment to provide insulation, and wicking for cold weather riding.
Of, pertaining to, or caused by heat or temperature

Thermal Collector
Thermal conduction
Heat transfer within a substance or to another substance by direct contact
Thermal convection
Heat transfer by the combined mechanisms of fluid mixing and thermal conduction
Thermal cracking
A refining process in which heat and pressure are used to break down, rearrange, or combine hydrocarbon molecules. Thermal-cracking includes gas oil, visbreaking, fluid coking, delayed coking, and other thermal cracking processes (e.g., flexicoking).
Thermal deterioration
Loss of strength of carcass cords due to heat generated in a tire.
Thermal efficiency
  1. The percentage of the heat developed in the burning fuel charge that is actually used to develop power determines thermal efficiency. When fuel is combusted in an engine not all the fuel is converted into power. Some is lost in overcoming friction and some escapes down the Tail pipe in the hot exhaust gases so this percentage is always less than 100%. Efficiency will vary according to engine design, use, etc. If an engine uses a great deal of the heat to produce power, its thermal efficiency would be high.
  2. A measure of the efficiency of converting a fuel to energy and useful work; useful work and energy output divided by higher heating value of input fuel times 100 (to show percent).
  3. Efficiency with which a power source transforms the potential heat of its fuel into work or output, expressed as the ratio of the useful work done by the power source in a given time interval to the total heat energy contained in the fuel burned during the same time interval, both work and heat being expressed in the same units.
Thermal equilibrium
The point at which the rate of cooling becomes equal to the rate of heat generation in a tire. Also called heat balance.
Thermal expansion coefficient
The characteristic of a material (esp. metal) to change its length or width as the temperature is increased or decreased. Different metals expand at a different rate when the same temperature change is applied.
Thermal head
The initial temperature of exhaust gas upstream of a catalytic converter
Thermal ignition control
(TIC) device used by Chrysler that shifts the vacuum advance vacuum source from ported vacuum to manifold vacuum when coolant temperature exceeds 107°C
Thermal inertia
The reciprocal of Thermal response
Thermal insulation
Material which is a poor conductor of heat; used to retard or slow down flow of heat through wall or partition.
Thermal limiter
Fuse-like device that protects the low refrigerant protection system circuit on GM vehicles. Stops compressor operation when low pressure is sensed

Thermally-actuated element
That part of a control device which is directly acted upon by temperature changes and originates or supplies motion or energy directly or indirectly to operate a control device (valve, switch, etc.).
Thermal management
The directing of heat entering or exiting a system.
Thermal Output
Thermal Panels
Thermal Parabolic Dishes
Thermal protector
A protective device, built into the electric motor, that disconnects the motor from its power source if the temperature becomes excessive for any reason
Thermal radiation
Heat transfer from one substance to another by means of electromagnetic waves
Thermal reactor

  1. A high-volume thermally isolated chamber replacing the exhaust manifold and providing a place for high-temperature afterburning of exhaust pollutants. Found on all Mazda rotary engines and some piston engines (BMW for example) as well.
  2. A device installed in the exhaust manifold of some air injection systems to promote HC and CO oxidation by providing long exhaust gas residence times in a localized area.
  3. An emission control device that accepts raw exhaust gases from the engine and subjects them to extremely hi temperature to oxidize noxious emissions. Uses a specially designed exhaust manifold that uses heat and air to burn the unburned hydrocarbons in the exhaust gases to reduce pollution
Thermal relay
  1. A relay actuated by the heating effect of the current flowing through it
  2. A Heat-operated electrical control used to open or close a refrigeration system electrical circuit. This system uses a resistance wire to convent electrical energy into heat energy.
Thermal resistance
(R-Value) This designates the resistance of a material to heat conduction. The greater the R-value the larger the number.
Thermal response
The rate of temperature rise in a reactor if no heat is withdrawn by cooling. Its reciprocal is thermal inertia
Thermal storage
Storage of heat or heat sinks (coldness) for later heating or cooling. Examples are the storage of solar energy for night heating; the storage of summer heat for winter use; the storage of winter ice for space cooling in the summer; and the storage of electrically-generated heat or coolness when electricity is less expensive, to be released in order to avoid using electricity when the rates are higher. There are four basic types of thermal storage systems: ice storage; water storage; storage in rock, soil or other types of solid thermal mass; and storage in other materials, such as glycol (antifreeze).
Thermal switch
A bimetal switch that controls glow plug operation
Thermal time valve
A valve which senses temperature, typically the temperature under the hood, and gives full vacuum advance when the temperature is below 5.5°C above this temperature, the thermal time valve allows the distributor vacuum to be controlled by the thermal vacuum switch; includes a delay of typically 20 seconds to allow full spark advance for better hot starting
Thermal unit
Thermal vacuum switch

  1. Measures either air/fuel temperature, underhood temperature, or coolant temperature, or a combination of any two to regulate the EGR valve accordingly.
  2. A temperature sensitive switch that shifts the source of the advance from ported to manifold vacuum when coolant temperature reaches approximately 107°C
  3. A vacuum switch that controls vacuum levels or routing based on coolant or ambient air temperature.
Thermal vacuum valve
(TVV) A valve with the same function as a thermal vacuum switch. TVS units, which serve to interrupt exhaust gas recirculation when the temperature is too low, are located in the vacuum line between the ECR valve and inlet manifold or carburetor
Thermal Value
Calories per gram of BTU per pound produced by burning fuels.
Thermal vent valve
(TVV) a temp-sensitive valve assembly located in the canister vent line. The TVV closes when the engine is cold and opens when it is hot to prevent fuel tank vapors from being vented through the carburetor fuel bowl when the fuel tank heats up before the engine compartment
  1. Resistor that changes its resistance inversely with temperature
  2. A temperature-sensitive, heat-activated resistor. Use in air conditioning system sensors.
  3. Basically a semiconductor which has electrical resistance that varies with temperature.
  1. An electrical temperature sensor. As opposed to a resistance thermometer, the thermocouple operates without an external voltage; it consists basically of two conductors of dissimilar metals, typically copper/constantan, iron/constantan, nickel-chromium/nickel, which are connected at their ends; one joint, the hot junction, is exposed to the temperature to be measured, the other joint, the cold or reference junction, is held at a fixed, known temperature; a thermoelectrical voltage is developed between the two junctions which is proportional to the temperature difference between the junctions
  2. Device which generates electricity, using principle that if two unlike metals are welded together and junction is heated, a voltage will develop across the open ends.
  3. A junction of two dissimilar materials which generates a minute voltage in proportion to its temperature. Such devices may be used as a signal source in indicating instruments and control equipment
Thermocouple spark plug
A spark plug with a thermocouple in the center electrode, used to measure the temperatures in the individual cylinders as a function of engine speed and load in order to select the correct heat range
Thermocouple thermometer
Electrical instrument using thermocouple as source of electrical flow, connected to milliammeter calibrated in temperature degrees.
Thermodisk defrost control
Electrical switch with bimetal disk controlled by temperature changes.
  1. Part of science which deals with the relationships between heat and mechanical action.
  2. A study of the transformation of energy from one form to another, and its practical application.
Thermoelectric refrigeration
Refrigerator mechanism that depends on Peltier effect. Direct current flowing through electrical junction between unlike metals provides heating or cooling effect depending on direction of current flow.
The shaping of a polymer sheet while heating
Device for measuring temperatures.

Number of thermocouples used in parallel to achieve low temperatures.
Number of thermocouples used in series to create a higher voltage.
Thermophotovoltaic cell
A device where sunlight concentrated onto a absorber heats it to a high temperature, and the thermal radiation emitted by the absorber is used as the energy source for a photovoltaic cell that is designed to maximize conversion efficiency at the wavelength of the thermal radiation.
A plastic material with long chain-like molecules that can repeatedly be softened by heating and hardened by cooling; most plastic parts used on vehicles are made of thermoplastics
Thermoplastic elastomers
Materials which are rubbery at room temperature but which on heating melt to viscous liquids that can be molded and otherwise processed; the change is reversible; on cooling, the melted material reverts to a solid material having rubbery properties
Thermos bottle
Trucker slang for Tanker truck as in ‘We just bought fifteen new thermos bottle’s.’
A polymer which sets at the same time as it is being molded
Thermosiphon system
A solar collector system for water heating in which circulation of the collection fluid through the storage loop is provided solely by the temperature and density difference between the hot and cold fluids.
  1. A temperature sensitive device used in the cooling system of an engine to control the flow of coolant between the cylinder block and radiator. It is set into the engine block and shuts off the circulation of water until the temperature of the water reaches the point at which the thermostat is set to open. Because automotive internal combustion engines operate more efficiently when their temperature is maintained within narrow limits, the thermostat closes off the flow of coolant from the engine to the radiator until the engine has reached the desired operating temperature. Other thermostats are used in the electrical circuit of the vehicle heating system to control the amount of heat supplied to the passengers, in the Manifold heat control system that preheats the air-fuel mixture going to the cylinders and in the Automatic choke.
  2. Device which senses ambient temperature conditions and, in turn, acts to control a circuit.
Thermostatic air cleaner
(TAC) An air cleaner which also controls the temperature of the air entering the engine. A temperature control is necessary to optimize the air/fuel ratio with regard to minimum exhaust emissions; typically, the TAC regulates air intake temperature at about 27-46°C by means of a control damper that mixes pre-heated air from an inlet at the exhaust manifold with air from a cold air inlet; designs for actuating the damper range from simple thermostatic action to vacuum-motor and stepper-motor control
Thermostatic coil choke
A sensing device mounted on the carburetor that automatically controls the ChokeButterfly valve by sensing the heat of the exhaust manifold.


Thermostatic control
Device which operates system or part of system based on’ temperature change.
Thermostatic expansion valve
  1. Metering device that removes pressure from liquid refrigerant, permitting it to expand and vaporize in evaporator
  2. Control valve operated by temperature and pressure within evaporator. It controls flow of refrigerant. Control bulb is attached to outlet of evaporator.
  3. A component which regulates the rate of refrigerant flow into the evaporator as determined by the outlet pipe temperature sensed by the remote bulb.
Thermostatic interruptor
A bimetallic circuit breaker in a lighting circuits which switches to an alternative circuit in the event of a fault or short circuit
Thermostatic motor control
Device used to control cycling of unit through use of control bulb. Bulb reacts to temperature changes.
Thermostatic spring choke
A sensing device that automatically controls the ChokeButterfly valve by sensing the heat of the exhaust manifold.


Thermostatic switch
A temperature sensitive switch that prevents icing by cycling compressor operation to control system temperature. Bellows and bimetallic switches are typical examples.
Thermostatic vacuum switch
A temperature sensitive switch which allows spark advance when engine idles for long periods
Thermostatic valve
Valve controlled by temperature change response elements.
Thermostatic water valve
Valve used to control flow of water through system, actuated (made to work) by temperature difference. Used in units such as water-cooled compressor and/or condenser.
A method of cooling an engine using difference in specific gravity and cold water. No pump is used, but the coolant passages are larger than in a pump-type system
Thermosyphon cooling
A natural cooling, using the fact that two columns of liquid at different temperatures possess natural circulation because the hotter column weighs less on account of its lower density; thus the hot engine must be located at a lower level than the cool radiator
Thermo-time switch
A switch in a continuous injection system that interrupts current from the starter solenoid to the cold-start valve solenoid when the engine is hot or after the starter has been operated for more than a few seconds, in order to prevent flooding
A valve which opens and closes as a function of temperature
  1. A space which accommodates a temperature sensor.
  2. The temperature sensing point or sensor rather than to the well itself
Thick film integrated
(TFI) Ford electronic ignition system
Thickness Flare
Thickness Gauge
Thickness of Thread
The distance between the flanks of the thread measured at a specified position and parallel to the axis.
To add thinners to paint in order to adjust the viscosity
Thin needle-nose pliers
A needle-nose pliers with an extra long reach jaws without a wire cutter
The Solvent used to thin Lacquers and acrylic products to the proper consistency for application and differs from a reducer which are used for synthetic enamel products. Thinners and reducers are not normally interchangeable, i.e., the corresponding type of thinner/reducer must be used for each type of paint; however, some general-purpose thinners are available.

Thinning out
The tendency of liquid paint to form much thicker coatings near the edge of a steel sheet, thereby causing the paint film thickness on the side opposite this edge to decrease
Thin-wall casting
A weight-saving measure on oil filter housings
An intermediate gear used for increasing speed, climbing hills and sometimes for passing; but on a three speed transmission, it is the top gear.
Third brush
A Generator in which a third, movable Brush is used to control current output.
Third gear
An intermediate gear used for increasing speed, climbing hills and sometimes for passing; but on a three speed transmission, it is the top gear.
Third hand
A tool used on bicycles to squeeze the brakes together against the rim so that adjustments can be made to the cable.
Third motion shaft
Third port induction
A design feature of a two-stroke engine that relies on the piston position to control induction of the fresh charge. A feature of this design is the use of the third port, i.e., the transfer port, to complement the intake and exhaust ports, e.g., as opposed to two-stroke diesels that have valve-controlled intakes and do not need transfer ports
Third scavenging port
An additional transfer port located opposite the exhaust port of a two-stroke engine cylinder and connecting through the piston skirt to the region above the gudgeon pin and below the piston crown
Having the property of certain resins and paints that prevents them from running off vertical surfaces
Abbreviation for Turbo Hydra-Matic
Thompson rotovalve
A type of valve which rotates as it opens and closes.
An abbreviation for thousandth or one divided by a thousand; a small measurement representing 1/1000th of an inch as in Ten thou (0.01) is equal to 0.25 mm.’
A colloquial term for pushing an engine to its limits
  1. The spiral grooves on a screw, bolt, or nut.
  2. Helical groove in a cylindrical hole, nut, etc., formed a tap or lathe tool (female or internal thread).
  3. Class 1 threads are a loose tolerance. Class 2 threads comprise 90% of stainless fasteners and are normal commercial tolerance. Class 3 threads have a stricter tolerance and tighter fit such as socket cap and set screws. No definite relationship exists between tensile strength and tightness or looseness of fit. The symbol ‘A’ added to threads, such as 2A, means external threads (screws), and ‘B’ means internal (nuts). With the exception of 10/32 diameter, which is extremely popular, coarse thread comprises 90-95% of hex head cap screws and hex nuts sold in 18-8 stainless, and perhaps 98% of other stainless items including machine screws and socket products. Coarse threads are deeper than fine threads with fewer threads per inch, so coarse threads may have greater protection against thread stripping, better tap in brittle materials, and better fatigue resistance, while fine threads may have better fit in thin-walled materials, higher torque strength, and increased tightness during vibration.
Thread angle
The angle between the adjacent flanks of a thread

Thread Chasers
Thread crest
The highest point of a screw thread, opposite the root
Thread-cutting screw
A British term for a Self-tapping screw. A self-drilling fastener that drills its own hole, taps a mating thread, and then fastens, all in a single operation
Thread diameter
The diameter measured from the crest of a thread to the corresponding crest on the opposite side of the bolt or screw.
Threaded headset
A headset at the top of the steerer tube with threads cut into it to accommodate a threaded fork. This system is found on road bicycles while threadless headsets are used on mountain bikes. A threaded headset must be used with a threaded fork. Threaded forks are most commonly found on road bikes. The threaded portion of the fork is located at the top of the steerer tube. For forks with threaded steerer tube The adjustable race screws on to the steerer, and a locknut screws on after the adjustable race to secure it. There is normally a keyed washer between the adjustable race and the locknut for extra security.
Threaded insert
A threaded coil that’s used to restore an original thread size hole that has damaged threads; the hole is drilled oversize and tapped, and the insert is threaded into the tapped hole
Threaded rod
Two types are available: a shaft (usually fairly long) with continuous threads from one end to the other or one with threads at both ends and a non-threaded body between them. It is usually cut to the length required. It is used for bolting in a tapped hole with one nut or drilled hole with two nuts. Used for flange bolting.
Threaded Spacers
Spacers with threads through which a bolt can be put. This saves weight by eliminating the nut and the reduction of the bolt length.
Threaded stem
A bicycle handlebar stem with threads which is inserted into the fork steerer tube. Also called quill type.
Threaded Taper Pin
Dimensioned the same as a standard plain taper pin with the addition of a threaded section usually at the small end. Used in equipment where removal may be required.
Thread file
A tool for restoring internal or external threads by filing
Thread form
Thread gauge
Thread height
The distance from root to thread crest, measured perpendicular to the axis of the thread

Thread insert
A screw-thread system that allows the use of high-strength cap screws and studs in light soft metals, such as aluminum and magnesium, through the use of a phosphor bronze or stainless steel coil which is screwed into a threaded hole; the thread insert can also be used to repair damaged threads
Threadless headsets
A bicycle headset which accommodates forks with an un-threaded steerer tube.
Threadless stem
A bicycle handlebar bar stem that bolts directly to the fork steerer tube. Originally developed for use on mountain bikes but becoming more and more common on road bikes.
Thread Milling
A machining process whereby thread is formed on a surface by generating with a rotating toothed cutter. Each tooth takes an individual chip.
Thread pitch

Thread pitch gauge
Thread Rolling
A cold-forging process whereby screw threads are formed by displacement of metal as opposed to cutting. The process is usually used for producing external threads and is seldom practical for small quantities.
Thread root
The lowest point of a screw thread, where the thread joins the body. It is opposite to crest
Thread Series
Groups of diameter-pitch combinations distinguished from each other by the number of threads per inch applied to a specific diameter.
Threads Per Inch
The reciprocal of the lead in inches.
Thread Thickness
The distance between the flanks of the thread measured at a specified position and parallel to the axis.
Thread Truncation
Three And Four-port
Three-chamber system
A test installation consisting of a salt spray chamber, a cold chamber, and a climatic chamber
Three-circuit-split brake system
Unique to the Teves anti-lock system. Uses the two hydraulic circuits of a dual master cylinder to individually actuate the front brakes, while the rear brakes are actuated by pressure from the hydraulic brake booster.
A spoking pattern in which a spoke passes over two and under a third spoke before being attached to the rim
A subcompact hatchback with two side doors and one liftgate
Three-door hatchback coupe
Three-door hatchback coupeThree-door hatchback coupe

Originally a small opening in the deck of a sailing ship, the term hatch was later applied to airplane doors and to passenger cars with rear liftgates. Various models appeared in the early 1950s, but weather-tightness was a problem. The concept emerged again in the early 1970s, when fuel economy factors began to signal the trend toward compact cars. Technology had remedied the sealing difficulties. By the 1980s, most manufacturers produced one or more hatchback models, though the question of whether to call them ‘two-door’ or three-door never was resolved. Their main common feature was the lack of a separate trunk. Liftback coupes may have had a different rear-end shape, but the two terms often described essentially the same vehicle.

Three-link suspension
A variation on the Four-link suspension. An upper link is typically removed. This arrangement was used on lower powered cars to reduce cost.
Operating by means of combination of three alternating current circuits which differ in phase by one-third of a cycle.
Three Phase Controller
An electronic circuit for controlling the output frequency and power from a 3-phase inverter.
Three phase electrical
A combination of three circuits energized by alternating electromotive forces that differ in phase by one third of a cycle.

Three-phase four wire system
A system of alternating-current supply comprising four conductors, three of which are connected as in three-phase three-wire system, the forth being connected to the neutral point of the supply, which may be grounded.
Three-phase power
Power generated and transmitted from generator to load on three conductors.
Three-phase three wire system
A system of alternating-current supply comprising three conductors between successive pairs of which are maintained alternating differences of potential successively displaced in phase by one-third of a period.
Three-piece alloy wheel
A type of forged alloy wheel with a wheel spider or wheel disc and a divided rim consisting of an outer and an inner rim well; the rim is bolted to the spider or the disc
Three-point seat belt
A combined lap-shoulder belt fastened at three points, usually with an automatic retractor
Three-port engine
The traditional two-stroke engine design incorporating the intake port connecting the crankcase to the atmosphere, the transfer port connecting the crankcase to the combustion chamber, and the exhaust port to evacuate the spent gas from the combustion chamber. The term is used even if the three-port types are used in pairs
Three-quarter cam
A type of camshaft for race car engines which increases lift of valve, speed of valve opening and closing, length of time valve is held open, etc. Also called Full camRace cam or Semi-race cam depending upon design
Three-quarter floating axle
A rear axle assembly in which the weight of the vehicle is borne by the outer bearings of the axle shafts, mounted between the hubs and axle housing
Three-quarter race camshaft
A description of the Customcamshaft indicating the type of lobe grinding which, in turn, dictates the type of use. Other grinds are one-quarter race, full-race, street-grind, etc.
Abbreviation for Three-speed, either manual transmission or automatic transmission.
Three speed
A transmission which has three forward gears.
A transmission which has three forward gears.
Three-speed transmission
A transmission which has three forward gears.
Three-valve engine
An engine with two intake valves and one exhaust valve per cylinder. A four-cylinder three-valve engine is also called a 12-valve engine
Three-way catalyst
(TWC) A catalyst for the simultaneous conversion of the three exhaust pollutants HC, CO, and NOx
Three way catalytic converter
Three-way catalytic converter
A pollution control device which reduces all three noxious substances HC, CO, and NOx.
3-way catalytic converter
Three-way valve
  1. Multi-orifice (opening flow control valve with three fluid flow openings.
  2. A hydraulic system component incorporating metering, proportioning, and warning light activation.
  1. A light car with three wheels; formerly made popular by some British vehicles like the Morgan, the BSA, the Coventry Victor, and the Reliant Robin.
  2. A modified motorcycle which has one wheel in the front for steering and two at the back driven by a Volkswagen engine.
Three Wire System
Threshold Limit Value
(TLV) Time-weighted average concentration of an air pollutant at the workplace for a conventional 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed without adverse health effects.
Throat depth
An indicator of the reach of welding clamps such as C-clamps
Throat of a fillet weld
Distance from the weld root to the weld face.
A rough-sounding exhaust noise which is pleasant to some and irritating to others.
The device that controls the vacuum created in the Venturi of the carburetor. The greater the vacuum, the richer the fuel-air mixture. The throttle enables the engine to run on a richer mixture and produce more power for high-speed driving. It consists of a Throttle arm located on the outside of the carburetor and connected to the gas pedal (or throttle twist grip on a motorcycle), which in turn activates a throttle Butterfly valve at the base of the Carburetor barrel where it joins the intake manifold.

Throttle arm
The lever that actuates the throttle.
Throttle body
A housing containing a valve to regulate the airflow through the intake manifold. The throttle-body is usually located between the air cleaner and the intake plenum.
Throttle body fuel injection
A form of fuel injection in which the injectors are located at the engine’s throttle body thereby feeding fuel to more than one cylinder. Such an arrangement saves money by using fewer injectors; but because it routes both fuel and air through the intake manifold it eliminates some of the tuning possibilities offered by port fuel injection. Also called Single point injection
Throttle body injection
Throttle butterfly
A valve in the throat of the carburetor which regulates the amount of the flow of gasoline.

Throttle enrichment
Throttle gauge
A tool with straight calibrated measuring pins for determining throttle and choke valve gaps
Throttle kicker
Throttle kickerThrottle kicker

A sensor that uses a vacuum diaphragm to push a rod against the throttle linkage to increase idle speed. A solenoid valve controls vacuum supply.

Throttle microswitch
A device that signals the ECU as to how far the throttle flap is closed so that the ECU can determine the spark advance points or the fuel injection cut-out on deceleration.
Throttle pedal
The foot operated lever (also called gas pedal) which operates the throttle butterfly through a series of linkages.

Throttle position sensor
Throttle position sensorThrottle position sensor


  1. A potentiometric fuel injection switch with two contacts for the two end positions of the throttle valve, which sends a signal to the electronic control unit when the throttle valve is closed (idle) or wide open (full load). The sensor wiper position is proportional to throttle position. The computer uses this information to control fuel flow
  2. A detection device which provides information on the position of the throttle actuation system.
Throttle potentiometer
A device that provides the ECU with a variable voltage signal of the throttle flap position so that the ECU can determine the dynamic spark advance required and the full load enrichment
Throttle relaxer
A device that mechanically controls throttle position during traction control system operation.
Throttle return spring
A spring which forces the throttle valve closed when pressure is taken off the accelerator pedal. See Throttle rod image.
Throttle rod. Click image to supersize
Throttle rod
An accelerator linkage connected to the carburetor or injection system.
Throttle shaft
A shaft on which the throttle valve disc pivots in a carburetor barrel or inlet tract
Throttle solenoid
A solenoid which operates mechanically on the throttle lever; when energized, the solenoid stem extends and opens the throttle to establish the preset idle speed. Since the early 1970s, most manufacturers have used a throttle solenoid to prevent run-on or dieseling
Throttle spindle
A shaft on which the throttle valve disc pivots in a carburetor barrel or inlet tract
Throttle stop solenoid
A device that maintains engine at speed over curb idle
Throttle switch
Throttle valve
  1. A valve in the carburetor. It is used to control the amount of air-fuel mixture that reaches the cylinders. Usually consists of a flat round disc mounted on a shaft so that it can be tilted at various angles in the carburetor throttle valve body. It is connected by suitable linkage to the accelerator pedal.
  2. A modulator valve in an automatic transmission which is actuated either by the accelerator pedal, by the vacuum in the engine intake manifold, or by the carburetor throttle; it converts line pressure into an engine-load dependent pressure, which is directed to various valves
Throttle valve switch
  1. Reducing the power output of an engine by closing the throttle, thus restricting airflow through the carburetor or intake tract.
  2. Expansion of gas through orifice or controlled opening without gas performing any work as it expands.
Throttling valve
Through bolt
  1. Any bolt which is inserted through the parts of an assembly and secured on the other side by a nut.
  2. One of the two long bolts that holds the starter or alternator assembly together
A broad highway designed for high-speed traffic
  1. The offset portion of the crankshaft designed to accept the Connecting rod.
  2. The distance from the center of the crankshaft Main bearing to the center of the Connecting rod Journal. The piston stroke is twice the throw distance.
Elongating certain sections of a panel by hammering. Opposite to Tucking. When making a section rounded along the inner and outer edges that is to be folded along the outer edge, the length of the outer edge must be increased. This is achieved by regular hammering, which causes the edge of the panel to stretch, reducing its thickness by spreading the metal
Throwing a rod
The action of breaking a connecting rod. Often the rod will force its way out of the side of the engine resulting in major damage which is expensive to repair. In most cases the rod breaks because of the lack of enough oil to cool the rod.
Throwout bearing
Throw-out bearing
Throw-out bearingThrow-out bearing

A part of the clutch activated by the Clutch pedal that allows the clutch to disengage. If you allow the vehicle to idle in gear with the Clutch pedal depressed, instead of shifting to neutral gear, you can wear out the throwout bearing. The British term is Clutch release bearing.

Throw-out fork
Throwout fork
Throwout lever
To surge powerfully upward or press outward.

Thrust angle
A locational relationship between the front and rear sets of wheels
Thrust bearing
A bearing with Flanges on its two sides that prevents a shaft such as the crankshaft from moving endwise. In the engine crankshaft assembly these Flanges are a close fit to the two sides of the Crankpin. If the crankshaft tends to shift one way or the other the Crankpin sides come up against the flanges preventing excessive endwise movement.

Thrust belt
Thrust load
A load applied in line with an axis of rotation.
Thrust plate
Thrust washer
  1. A Bronze or a hardened steel washer placed between two moving parts. The washer prevents longitudinal movement and provides a bearing surface for the thrust surfaces of the parts.
  2. An axially loaded washer, e.g., of a shaft bearing
A broad highway designed for high-speed traffic
Thumb nut
A nut or screw with projections enabling it to be turned by thumb and forefinger; a wing nut/screw
thumb screwThumb screw

A nut or screw with projections enabling it to be turned by thumb and forefinger; a wing nut/screw

Thumb shifter
A shifter designed to be operated with the thumbs, such as Shimano Rapid Fire models or Sturmey Archer three-speed models
A small wheel for adjusting, which can be turned by using the thumb and forefinger
A motorcycle with large-displacement, single-cylinder, four-stroke engine.
Ford ThunderbirdClick image for books on
Ford Thunderbird

A vehicle brand of which the 1955-57 and 1958-60 models are milestone cars.

A silicon-controlled rectifier which converts alternating current to a unidirectional current
Thyristor ignition
A Capacitor discharge ignition
Abbreviation for Transistorized ignition
Abbreviation for Breaker-triggered transistorized ignition
Abbreviation for Thermal ignition control
A notice of a violation of a traffic law

A carburetor starting aid. When starting at low temperatures, the float may be pushed below the fuel level in the float chamber by depressing the tickler, so that more fuel is supplied than is required for normal operation
Tick over
  1. To run at low speed with the throttle control closed and the transmission disengaged.
  2. To idle
The speed of an engine when it is turning over
A device for securing a load usually made of straps and hooks.
Tie-down system
Equipment which secures someone who uses a wheelchair to the floor of the van or bus. There are many kinds of devices used including brackets, straps, wheel locks, and belts.
Tie rod
  1. Any connecting red or bar, usually under tension.
  2. A rod, or rods, connecting the steering arms together. It links the pitman arm and the idler arm to the steering knuckle arms. When the tie rod is moved, the wheels pivot.
Tie rod arm
Tie rod end
Tie rod ends
A type of Ball joint which transfers the movements of the steering wheel to the wheels. Grease fittings or Ball joints located on the ends of the Steering linkage.
Tie rod puller
A special automotive tool for forcing out joints on tie rod ends by screw action
Tie rod separator
A special automotive tool for forcing out joints on tie rod ends by screw action
Tier 1 Supplier
Manufacturer to the vehicle assemblers who are responsible for delivery of the finished assembly, product development and continued technology renewal.
Tier 2 Supplier
Producer of parts providing value-added to minor sub-assembly.
Tier 3 Supplier
Supplier of engineered materials and special services, such as rolls of sheet steel, bars and heat treating, surface treatments.
Abbreviation for Traffic Impact Fee
Term used to describe gas tungsten inert arc welding (tungsten inert gas).
  1. A handling condition in which the car’s front end wants to go straight when the wheel is turned. Also called understeer or push.
  2. A description of a vehicle indicating its ability to easily negotiate curves at high speed.
TIG welding
An inert arc welding method using a tungsten electrode
Abbreviation for Transistorized ignition with hall generator
Abbreviation for Transistorized ignition with inductive pick-up
Tijuana taxi
Trucker slang for Well marked police car as in ‘There’s a tijuana taxi about a mile ahead.’.
Tile setter hammer
A hammer used to secure tile
  1. Abbreviation for Tilt steering wheel.
  2. A cab which tilts up for maintenance. It does not mean the vehicle is necessarily a COE. The engine cowls of some conventional power units tilt although the entire cab does not.
Tilt Body
A flatbed for hauling equipment. Sometimes specialized dumps are called this.
Tilt column
A steering column that can be adjusted for height
Tilt/slide sunroof
A sunroof, made of steel or glass, that slides and tilts and is operated either manually or electrically
Tilt steering wheel
(tilt) A steering wheel which moves up or down or which can be set at a different angle. In this way, the driver can find the most comfortable position and also allows easier entry and exit from the vehicle.
Time delay relay
A relay which responds to a signal with a certain delay. In some ignition systems, a time delay relay allows for full vacuum advance 20-30 seconds after start-up, after which control is again taken up by the TCS; some cars have an additional time delay relay which delays vacuum advance about 30 seconds after the transmission has been shifted to high gear
Timed fuel injection
Timed injection
Clock-operated mechanism used to control opening and closing of an electrical circuit.

Timer core
A magnetic pick-up assembly.

Thermostat control which includes a clock mechanism. Unit automatically controls room temperature and changes temperature range depending on time of day.
Time To Repair
Time Trial
(TT) A competition where a vehicle seeks to cover a certain distance in the best time possible. In most cases the vehicle proceeds solo (i.e., other vehicles are not on the track at the same time)
Time valve
  1. The capability of the valves, ignition system, and other engine-driven parts of a vehicle to work together for maximum efficiency.
  2. One of the essential factors in an internal combustion engine (Fuel, Air, Proper proportion of mixture, compression Timing, spark). When the piston is in the compression stroke both valves must be closed. If one or more is open, the Valve timing is out. Perhaps a Timing belt or Timing chain has jumped a tooth. If the spark does not arrive at the correct moment, the engine is out of time. If this ignition timing is only slightly off, the engine may run with less efficiency. Ignition timing is regulated by checking it with a timing light and then adjusting the distributor.
Timing belt
A toothed belt driven by the crankshaft and operates the camshaft. It causes the valves to open and close at the proper time. When an engine is rebuilt, it is important to line up the crankshaft Sprocket with the camshaft sprocket before applying the belt. When the belt breaks, often a valve will remain open and be hit by the rising piston causing the valve to bend and other internal damage.

Timing belt pulley
A spring-loaded jockey pulley or idler pulley designed to take up the slack in the timing belt
Timing belt tensioner
A spring-loaded jockey pulley or idler pulley designed to take up the slack in the timing belt
Timing chain
A drive chain driven by the crankshaft and operates the camshaft. It causes the valves to open and close at the proper time. When an engine is rebuilt, it is important to line up the crankshaftSprocketcamshaft sprocket before applying the chain. When the chain often a valve will remain open and be hit by the rising piston causing the valve to bend and other internal damage. In OHC engines, it is called a camchain chain or cam chain

Timing control
Timing diagram
A diagrammatic representation of the engine timing, i.e., the times during which the intake and exhaust valves are open and closed
Timing gear
Both the gear attached to the camshaft and the gear on the crankshaft. They provide a means of driving the camshaft. This system is used where long life and hard service are expected as in commercial vehicles and race cars. Using gears is generally a noisier method than using a Timing chain or a Cog belt to drive the camshaft.
Timing gears
Timing gun
Timing light
A stroboscopic unit that is connected to the secondary circuit to produce flashes of light in unison with the firing of a specific spark plug. By directing these flashes of light on the whirling Timing marks the marks appear to stand still. By adjusting the distributor the timing marks may be properly aligned, thus setting the timing. xenon timing lights have the advantage over neon lights because they are more visible in daylight.
Timing mark
Timing marks
  1. Marks or notches, usually located on the Vibration damper used to Synchronize the ignition system so that the plugs will fire at the precise time.
  2. One tooth on either the camshaft or Crankshaft gear will be marked with an indentation or some other mark. Another mark will be found on the other gear between two of the teeth. The two gears must be meshed so that the marked tooth meshes with the marked spot on the other gear.
Timing Meter
Timing rotor
A rotating part of the pick-up assembly, in the form of a drum with ferrite rods embedded vertically in the outer edge, used instead of a trigger wheel
Timing shaft
Timing system
Timing valve
In Bosch CIS, a device that regulates pressure in the lower chamber of the differential-pressure valve, in response to a signal from the lambda (oxygen) sensor. Also called Lambda valve (Bosch’s term) or a Frequency valve
Timing window
Window through which it is possible to see the timing marks
Timken® bearing
A type of tapered roller bearing
Timken® roller bearing
A type of tapered roller bearing
A malleable and ductile metal which increases strength, hardness, and corrosion resistance against salt water when added to brass alloys.
Tin can
Trucker slang for CB radio as in ‘I have to get a new tin can at the next truckstop.’
Tin immersion treatment
A formation of a thin tin deposit before electroplating
Tin Lizzie
An affectionate name for the Model T Ford of which 15,007,033 were built.
Tinmen’s shears

Tinner’s hammer
A hammer used to shape tin plates
Tinners Rivet
A small rivet having a head of the same form as a flat head rivet but larger in diameter, used in sheet metal work.
Tinners snips

Coating a piece of metal with a very thin layer of Solder. This is a pretreating procedure before the application of body lead. To ensure that the body lead adequately covers and takes to the area to be repaired, a flux and a thin coating of tin or a special solder paint are applied
Tin snips

Tinted glass
A glass that has been specially colored to reduce glare from the sun
Tinted windows
A glass that has been specially colored to reduce glare from the sun
T intersection
T intersectionT intersection

A road that no longer goes straight ahead but turns either to the left or the right

A colloquial term for glass that has been specially colored to reduce glare from the sun
Tint tone
A shade produced when a small amount of color is mixed with a large amount of white; this is required for formulating the ingredients of a certain paint tone
The end of a spark plug insulator, nearest the electrode.

Rear/side tipper: Specialized dump rig, usually. A roll-off tipper is a roll-off container carrying setup.

Abbreviation for Total Indicator Reading. In disc brakes, this refers to a rotor runout reading of the entire swing of the dial indicator’s needle, both above and below zero.
  1. The rubber part of the wheel which contacts the ground. The construction can be Bias-ply Bias-belted or Radial. The plies are made of rayon, nylon, and polyester.Belting can be fiberglass steel, or kevlar. The rest of the tire is hard rubber.
  2. The rubber and cord donut on the wheel rim that is filled with pressurized air and transmits vehicle forces (including braking forces) to the road.
Tire aging
The deterioration of rubber properties by oxidation over a period of time.
Tire balance
Because tires turn at relatively high speeds, they must be carefully weighted so that they do not bounce or vibrate when they rotate. Two basic kinds of balancing are static balanceDynamic balance.
Tire bead
That portion of the tire that bears against the rim Flange. The bead has a number of turns of steel wire in it to provide great strength.
Tire bead lock
The tire bead and rim of a TD rim are designed so that an enlarged and reinforced toe on the tire bead engages in a small circumferential groove in the bead seat area of the rim; the bead thus remains locked in position under both inflated and deflated conditions
Tire body

Tire carrier
Tire casing
  1. The main body of the tire exclusive of the tread tube, etc.
  2. Layers of cord, called plies, shaped in a tire form and impregnated with rubber, to which the tread is applied.
Tire chains
Tire clearance
Tire contact area
Tire contact patch
The area of tire rubber that actually touches the road at any one time. Also called the tire footprint.
Tire contact zone
Tire deviation angle
An angle formed by the direction of travel of a vehicle and the steered direction (that which the wheels are pointing). It is produced by distortions within the tire, due to external forces. Not to be confused by actual slipping or skidding. Also called Slip angle.
Tire dressing
Paint, black glossy or dull finish, to improve appearance of tire sidewalls.
Tire footprint
Tire gage
Tire gauge
An instrument for determining the pressure in a tube or tire.
Tier growth
The stretching of textile tire cord materials due to heat and loss of strength, resulting in the Casing increasing in size.
Tire iron
  1. A tool for removing a tire from the rim of a wheel.
  2. A tool for removing the nuts holding a wheel to the hub since one end is flat and the other has a socket.
Tire jack
A device which is used to lift one corner of a vehicle so that a wheel can be removed and replaced in the event of a flat tire.


Tire kicker
A person who is just looking at a vehicle for sale but is not intending to buy.
Tire lever
A British term for a tool used to remove and install tires by lever action or to pry off parts.


Tire paint
A black paint, compatible to tire bodies, used to enhance the appearance of a tire after retreading.
Tire plies
The layers of nylon, rayon, etc., cloth that are used to form the casing. Most vehicle tires are two ply with a four ply rating. Two ply indicates two layers of cloth or plies.
Tire ply
Tire pressure
The manufacturer’s recommended pressure for a tire, dependent on load, speed, etc., usually given in bar or pound-force per square inch (psi). (1.8 bar = 26 psi; 2 bar = 29 psi; 2.2 bar = 32 psi; 2.4 bar = 35 psi; 2.7 bar = 39 psi)
Tire pressure gauge
An instrument for measuring air pressure in a tire
Tire Pressure Monitor System
(TPMS) Pressure sensors located in each wheel to directly measure the pressure in each tire and warn the driver when the air pressure in any tire drops at least 25% below the recommended cold tire inflation pressure identified on the vehicle placard.
Tire Pressure Warning
Tire, road
Tire roll-off
A condition in which the bead unseats because a tire was run while flat. Also, the sudden loss of air due to side forces, such as hard cornering, combined with underinflation. The Safety ledge on passenger rims (a necessity for tubeless mountings) guards against a roll-off.
Tire rotation
Moving the wheel and tire assemblies to different locations (e.g., front wheels to the rear and the rear to the front) to equalize any wear irregularities in the tires.

Tire scuff
Removal of some sidewall rubber as the tire drags along the edge of a curb.

Tire sidewall
That portion of the tire between the tread and the bead.
Tire size designation
A designation specified on the tire sidewall; e.g., P205160 R 15, where P=Passenger car; 205 = tire width in millimetres; 60 = tire section height to width ratio; R = radial ply; 15 = nominal rim diameter in inches
Tire Size Markings
Those designations that appear on the side of a tire to indicate its basic dimensions; width, and rim diameter.
Tire slip
The difference between the speed of the vehicle and the speed between the tire and the ground, expressed in a percentage.
Tire slip angle
Tire Speed rating
The maximum driving speed for which a tire is designed, indicated by a letter in the tire designation on the sidewall. The speed rating evolved gradually and is thus not directly proportional to the alphabetical order.

P = up to 150 km/h (95 mph)
Q = up to 160 km/h (100 mph)
R = up to 170 km/h (105 mph)
S = up to 180 km/h (113 mph)
T = up to 190 km/h (118 mph)
U = up to 200 km/h (125 mph)
H = up to 210 km/h (130 mph) also called high speed thus the ‘H’
V = up to 240 km/h (150 mph) also called very high speed thus the ‘V’
W = up to 270 km/h (168 mph)
Y = up to 300 km/h (186 mph)
Z = over 300 km/h (186 mph)
Tire spreader
Any device, manual or hydraulic, used to spread tire beads for inspection, repair, service, etc.
Tire squeal
The noise made by the tires when experiencing sudden acceleration or braking or when cornering too fast
Tire store
Retail outlet selling and installing tires and often offering other vehicle repair services.
Tire system
Tire tread
That part of the tire that contacts the road.
Tire tread gauge
Tire, triathlon
Tire tube
An inflatable rubber device mounted inside some tires to contain air at sufficient pressure to inflate the casing and support the vehicle weight.
Tire unbalance
A tire that is not weighted properly can cause vibration. The condition is exaggerated by centrifugal force which increases as speed is increased and by the distance the heave spot is from the wheel axis.
Tire valve
Tire valveTire valve

A small valve, mounted on the wheel rim of a Tubeless tire that allows air to be added to the tire with an air hose and allows air to be withdrawn from an over-inflated tire by pressing on the little stem at the end of the valve. Some tire valves have little caps to protect against leaks and keep dirt from fouling the valve. On tires with Inner tubes the tire valve is mounted on the inner tube. There are two kinds of valves used Presta and Schrader.

Tire wear
The amount by which, for example, the tread of a tire is worn down, or the sidewall damaged by impact with the curb
Tire width
The width of a tire measured across the carcass
The Industry Safety Council.
A silvery gray metal with high corrosion resistance against salt waters, chlorides, and many acids. It is strong, though lightweight, and very expensive.
Abbreviation for Thermactor Idle Vacuum Valve (Ford)
Joint formed by placing one metal against another at an angle of 90 degree. The edge of one metal contacts the surface of the other metals.
A junction where the meeting of a minor road with a major road forms a ‘T’ shape
Abbreviation for Throttle Kicker Actuator (Ford)
Abbreviation for Throttle Kicker Solenoid — An actuator moves the throttle linkage to increase idle rpm
Abbreviation for Truckload — The quantity of freight required to fill a trailer; usually more than 10,000 pounds. Compare LTL
TL Carrier
A trucking company which dedicates trailers to a single shipper’s cargo, as opposed to an LTL (Less Than Truckload) carrier which transports the consolidated cargo of several shippers and makes multiple deliveries.

Abbreviation for Transitional Low-Emission Vehicle
Abbreviation for Threshold Limit Value
Abbreviation for Tetramethyl lead
Abbreviation for Ton Mile Per Hour. A system devised to ascertain the working capacity of earthmover tires; it is a supplement to the normal load and inflation tables.
Tobin bronze
A type of brass containing 59-62% copper, 0.5-1.5% tin, and the rest is zinc. Especially good for resisting salt water conditions. Also called Admiralty brass or Naval brass.
The brake shoe end where the hydraulic or servo force is applied.

The front vertical panel that provides support for the pedals and for the front passenger’s feet, usually inclined towards the front and spot-welded to the floorboard at its bottom end and to the bulkhead at its upper end
Toe Clip
Toe Clip

The metal bracket attached to a bicycle pedal designed to maintain the cyclist’s foot in the correct position. It has a small loop at one end through which a strap is threaded to further secure the foot.

Toe clip pedals
Older style method of securely attaching your feet to the pedals through the use of clips and straps.
Toe control link
A Lateral link in a Multilink suspension designed to control a wheel’s direction as the suspension moves up and down.
Toe dolly
A flat slab of metal thinned down at one end and with a curved surface; useful for getting into awkward and narrow corners
Toe in


An adjustment of the front wheels where the distance from the center of the left wheel to the center of the right wheel is less at the front of the wheels than at the back of the wheels. A slight amount of toe-in is usually specified to keep the front wheels running parallel on the road by offsetting other forces that tend to spread the wheels apart. The major force is the backward thrust of the road against the tire tread while the vehicle is moving forward. Other factors include play in the tie-rod assembly and allowance for angular changes caused by wheel bounce or variations in road conditions. Toe-in is measured in fractions of an inch or millimetres.

Toe-in angle
The angle formed by each front wheel plane and the longitudinal axis of the car, usually expressed as the difference in distance between right and left wheel rims at front and rear, measured at hub level
Toe of weld
Junction of the face of the weld and the base metal.
Toe out

An adjustment of the wheels where the front of the wheels is further apart than the back. Generally toe-out is not desirable. Toe-out is measured in fractions of an inch or millimetres.


Toe out on turns
Toe-out on turns
When the vehicle negotiates a curve, the inner wheel turns more sharply and while the wheels remain in this position, a condition of toe-out exists.
Toe steer
The changes in the direction of a wheel that occur without driver steering input. Toe steer can be caused by Ride steer or by deflections in suspension components caused by the stresses of cornering, accelerating, and/or braking on smooth and bumpy roads.
Toe strap
A leather belt that attaches to a pedal cage and Toe clip to secure the foot to the pedal.
Toe wear
Abbreviation for Trailer On Flatcar — a method for moving cargo which involves transporting semitrailers on railroad flatcars.

Toggle switch
A switch that is actuated by flipping a small lever either up and down or from side to side.
  1. The amount of variation permitted from an exact size or measurement. The actual amount from the smallest acceptable dimension to the largest acceptable dimension. The difference between the permissible maximum size and the permissible minimum size of a measured quantity.
  2. A permissible variation, usually stated as limits of a specification.
  3. The total permissible variation of a size. The tolerance is the difference between the limits of size.
Tolerance Limit
The variation, positive or negative, by which a size is permitted to depart from the design size.
Money charged for the use of a road or bridge — especially for entering controlled highways and government parks
Toll road
A road (usually a highway) where access requires the payment of a toll or fee. The opposite is a Freeway
Toll sticker
A label or sticker displayed on the windshield indicating pre-payment of a toll
(C6H5CH3) Colorless liquid of the aromatic group of petroleum hydrocarbons, made by the catalytic reforming of petroleum Naphthas containing methyl cyclohexane. A high-octane gasoline-blending agent, solvent, and chemical intermediate, and a base for TNT (explosive).
Tomaso Pantera
Tomaso PanteraClick image for books on
Tomaso Pantera

A model of automobile manufactured in Italy

Tommy bar
  1. A rod that fits in a Box spanner.
  2. A short bar used as a lever to provide torque for tightening a box or socket spanner. Also called a crossbar
  1. A speed of 100 mph
  2. A measure of 2000 lbs, 2240 lbs, or 1000kg depending on the type of ton
Tone ring
The gear-like ring that spins its teeth trough the speed sensor’s magnetic field, causing generation of voltage by the sensor.
Tone wheel

Tongue weight
The amount of trailer weight supported by the hitch. Too much, and the rear of the tow vehicle will be overloaded; too little, and the trailer will wander and weave as it’s towed. Tongue weight should be between 10 and 15 percent of the total trailer weight.
Ton mile
The product of the distance that freight is hauled, measured in miles, and the weight of the cargo being hauled, measured in tons. Thus, moving one ton for one mile generates one ton mile.
Ton mile per hour
(TMPH) A system devised to ascertain the working capacity of earthmover tires; it is a supplement to the normal load and inflation tables.
A measure of the internal volume of spaces within a vessel in which 100 cu.ft. is 1 ton.

Tonnage certificate
Tonnage deadweight
Tonnage gross
Gross tonnage includes a ship’s internal volume, excluding such spaces as the peak, double bottom, deep tanks used only for water ballast, bridge, forecastle, open-ended poop, certain light and air spaces, skylights, anchor and steering gear spaces, toilets, the wheelhouse, and certain passenger spaces
Tonnage net
Net tonnage is the gross tonnage less certain additional spaces such as crew and officer spaces, chart room, and a percentage of the propelling machinery spaces.

Tonnage openings
Nonwatertight openings in the shelter deck and in the between deck bulkheads immediately below in order to exclude spaces from tonnage measurement and thus obtain reduced gross and net tonnage. The openings could be closed by nonwatertight wood shifting boards or metal covers meeting the tonnage and load line regulations
Tonneau cover
A cover of leather or other soft pliable material used for protecting the interior of a convertible when the soft top is down. The cover snaps to the dash sides, and rear of the vehicle and often has a zipper allowing the driver to operate the vehicle while the passenger side of the vehicle remains covered.
Ton of refrigeration
Refrigerating effect equal to the melting of 1 ton of ice in 24-hours. This may be expressed as follows 288,000 Btu/24 hr., 12,000 Btu/1 hr., 200 Btu/min.
Ton refrigeration unit
Unit which removes same amount of heat in 24-hours as melting of 1 ton of ice.
  1. As a noun, it is any device which assists in the installation or removal of a component.
  2. To work material by turning, milling, grinding, polishing, drilling, punching, boring, shaping, shearing, pressing, or planing.
  3. As a colloquial verb, it is the action of motion as in We were tooling down the highway when we saw you.
Tool bit
The hardened steel or carbide blade that cuts away metal during machining.
Tool cart
Tool cartTool cart

A tiered table (usually on wheels) designed to hold the pertinent tools for performing repairs on a vehicle.

  1. Set of required standard or special tools needed to produce a particular part. It includes jigs, fixtures, gauges, and cutting tools; but excludes machined tools.
  2. A colloquial term for driving, as in ‘I was tooling down the road when another car hit me.’

Tool marks
Scratches created by wrenches, etc. used to assemble, install, or remove components on an object.
Tool welding
Toothed belt
A positive-action reinforced rubber or plastic belt in which parallel teeth engage with grooves in a driving and a driven wheel; commonly used for the valve timing gear as an alternative to a roller chain
Toothed signal rotor
The component of an ABS system that rotates with the hub, driveaxle, axle, or ring gear, used along with the wheel speed sensors for generating impulses to the rear by the ABS electronic control unit (ECU). The ECU counts these impulses and determines if a wheel is decelerating too rapidly or not
Tooth heel
The wider outside end of the tooth in the differentialRing gear.
Tooth Lockwasher
A washer, usually a thin disk with prongs or projections, which is elastically deformed when assembled with a threaded fastener, so that the prongs, on which the pressure is localized, resist loosening of the fastener.
Tooth pliers
Tooth toe
The narrower inside end of the tooth in the differentialRing gear.
  1. A car roof, especially that of a convertible.
  2. The highest gear of a transmission.
Top cap
When retreading a tire, new tread rubber is added to the buffed Casing covering only the crown area.


Top carriers
A cage of chrome bars which attaches to the gutter rails on the roof of a car or van. It is used to secure loads on a vehicle roof, such as bulky containers, skis, or bicycles
Top case
A top case sits behind the passenger seat of a motorcycle and may be large enough to hold two full-face helmets. Like the tank bag, a top case is meant to hold lightweight items. Overloading a top case puts more weight on the rear of the motorcycle, thus lightening the front wheel. Traction and steering suffer when the top case is overloaded.
Top chop
A modification of the roof of custom cars. The roof pillars are cut off and shortened when the roof is welded back on, the roof line is far lower than before and the screen and side window height may have been reduced to a minimum. Due to problems of rigidity and finding suitable glass panes, this modification is extremely difficult
Top coat
A final paint coat
Top coat drier
An oven for drying or stoving the final paint coat
Top coat oven
An oven for drying or stoving the final paint coat
Top dead center
(TDC) Highest point of piston and connecting-rod travel in a cylinder; the ends of the compressionexhaust strokes in a Four-cycle engine.

Top electrode
The ground electrode protruding above the center electrode of a spark plug, either full coverage type or set back slightly from the far edge of the center electrode
Top end
  1. The upper range of engine revolutions.
  2. The upper part of the engine (pistons, cylinder, valve gear, induction system) from the base gasket to the valve cover
Top end gasket kit
The gaskets that apply to everything from the base gasket up (e.g., base gasket, head gasket, manifold gaskets, carburetor mounting gaskets) as well as all the O-rings and replaceable spacers. Contrasts with the Bottom end gasket kit.
Top end speed
The maximum speed which a vehicle can attain. This may differ from the maximum speed allowed by the law and from the recommended maximum speed of a vehicle. In some vehicles, governors are installed to limit the speed so that top end speed is not attained. Others may use warning lights or flashing Speedometer readings (i.e., on digital displays) or even warning sounds.

Top feed gun
Top gear
The highest available gear
Top hat section
A structural sheet metal member of U-section, but incorporating flanges for welding or assembling the section to a flat mating panel
Top land
Top off
Fill a partially filled container to full capacity.
Top-of-the-line model
The most powerful and expensive model in a particular manufacturer’s lineup of vehicles
Top-of-the-range model
The most powerful and expensive model in a particular manufacturer’s lineup of vehicles

Topped Crude Oil
Oil from which the light ends have been removed by a simple refining process. Also referred to as reduced crude oil.
Top ring groove insert
A piston ring that has a nickel-iron or comparable metal insert cast into the piston heads. The top ring groove is cut into this metal. As the top ring grooves in aluminum pistons pound out of shape, this insert groove will prolong the useful life of the piston and ring.
Top speed
The maximum speed of a vehicle
Top tints
The tinted stripe at the upper edge of the windshield
Top tube
On a bicycle the horizontal tube that connects the Seat tube with the Head tube.
Top up
To raise the level of a liquid in a container to the required level
Top up the battery
Determine if the electrolyte is at the correct level and add distilled water to bring it up if necessary
  1. The mechanism which the operator holds during gas welding and cutting, at the end of which the gases are burned to perform the various gas welding and cutting operations.
  2. A British term for a flashlight.

An iron donut that induces permeability like a pulse-type transformer

ToronadoClick image for books on

A model of automobile manufactured by the Oldsmobile division of General Motors from 1966-92. The 1966-67 Toronado models are milestone cars. Sometimes you will see this car incorrectly spelled Tornado in classified ads.

An open sports vehicle generally with an unbroken design line from the hood to the back of the car.
Torpedo body
An early type of touring car with a streamlined torpedo-like body
  1. Turning or twisting force such as the force imparted on the drive line by the engine. Usually measured in lb-ft. It differs from work or power in that torque does not necessarily produce motion. Basically, the magnitude of a torque acting on a body is the product of the magnitude of a force and its force arm (perpendicular distance from the axis of rotation of the body to the line of action of the force). This product is called the moment of the torque about the axis or the torque.
  2. To tighten a nut or bolt with a torque wrench.
  3. The turning or twisting force applied at the end of a rotating shaft. It is force applied multiplied by the torque arm. In the traditional system the units are pound-force-foot (or foot-poundforce). The units in the SI and metric systems are newton-metre or dyne-centimetre respectively.
Torque arm
  1. A T-shaped extrusion of the rear axle casing to take up forward thrust of the driven axle
  2. Defined as the distance from the center-point of rotation to the point at which the force is applied. If torque is being applied using a wrench, the length of the torque arm is the same as the length of the wrench.
Torque converter
A unit in an automatic transmission which is quite similar to the fluid coupling that transfers engine torque to the transmissioninput shaft. It also cushions the flow of power. Unlike the Fluid coupling the torque converter can multiply engine torque. This is accomplished by installing one or more Stators between the Torus members. In the torque converter the driving torus is referred to as the pump and the driven torus as the Turbine. The engine drives the Impeller which in turn impels fluid against the Vanes of a turbine connected through transmission gears to the driveshaft of the automobile. The stator redirects oil flow from the turbine to Boost impeller action and multiply engine torque.

Torque converter drive plate
Torque converter housing
A Bell housing
Torque converter lock-up clutch
An automatically engaged clutch in a lock-up torque converter which prevents slipping losses
Torque curve
A graph which shows the engine torque as a function of engine speed
Torque, full load
Maximum torque delivered without overheating.
Torque limiter
A tool used in conjunction with a plug wrench which allows the controlled tightening of spark plugs by releasing automatically once a preset torque setting is reached
Torque multiplication
Increasing engine torque in the automatic transmission through the use of a Torque converter.
Torque plate
Torque ratio
Torque rods
Torque screwdriver
A screwdriver with a device that measures the amount of torque being applied
Torque sensitive limited slip differential
A differential where the mechanism reacts to differences in torque when one wheel on an axle starts to slip, and limits the differential action to help maintain traction.
Torque sequence
The order in which a series of bolts or nuts should be tightened.
Torque split
Distributing torque between wheels on the same axle or between front and rear axles in a 4WD vehicle
Torque stall
The amount of force required to start a shaft turning. Once in motion, the amount of torque to keep the shaft turning is much less.
Torque, starting
Amount of torque available, when at 0 speed, to Stan and accelerate the load.
Torque steer
A tendency for a car to turn in a particular direction when power is applied. Torque steer is common in front-drive cars because reaction forces created in the half-shafts can generate uneven steering forces in the front tires.
Torque strength
Torque is the force used in twisting, such as tightening a fastener. Torsion strength is the amount of force needed to twist a fastener apart. Both measures consider the amount of pressure applied to the fastener and the length of the wrench used in the application.
Torque tube
A hollow forward extrusion of the rear axle casing incorporated in early live rear axle designs, both enclosing the drive shaft and providing a forward location of the driven axle, pivoting about a spherical joint either at the rear end of the gearbox or at the chassis frame
Torque tube axle
A live rear axle layout with a divided drive shaft and a T-shaped axle housing, the hollow forward extrusion of which carries the rear half of the divided drive shaft
Torque tube drive
The method of connecting the transmissionOutput shaft to the differentialPinion shaft by using an enclosed driveshaft. The driveshaft is enclosed in a torque tube that is bolted to the Rear axle housing on one end and is pivoted through a Ball joint to the rear of the transmission on the other. The driving force of the rear wheels is transferred to the Frame through the torque tube. This method was used on older cars in an attempt to get rid of the twisting forces of engine torque on the suspensiondriveshaft.
Torque wrench
A wrench with a dial in the handle or a gauge with a needle for measuring the amount of pressure applied to a nut or bolt. It is used for threaded fasteners with a critical tightening torque, such as cylinder head bolts, alloy wheel lugs, suspension links, etc.

An engine which develops high torque (i.e., it pulls well) at low speeds, relative to its power
Torsen differential
A torque-sensing differential system incorporating a worm and roller mechanism
Torsen four-wheel drive
Based on the principle that a worm gear can drive a roller but not vice versa, the Torsen differential balances different wheel speeds due to different travel distances, whereas speed differences due to differing adherence situations are not balanced. A permanently engaged four-wheel drive incorporating a Torsen differential
The strain on a part or component produced by torque
Torsional rigidity
The resistance against torsional loads, specified in newton-metre per angular degree of body twisting.
Torsional stiffness
The resistance against torsional loads, specified in newton-metre (or lbs-ft) per angular degree of body twisting
Torsional vibration
A twisting and untwisting action developed in a shaft. It is caused either by intermittent applications of power or load.
Torsional vibration damper
  1. Any device that reduces torsional vibrations.
  2. The small flywheel on the front end of a crankshaft
Torsion bar
Torsion barTorsion bar

A long Spring steel rod or flat bar attached in such a way that one end is anchored while the other is free to twist. One end is fastened to the frame at one end and to a suspension part at the other. If an arm is attached at right angles, to the free end, any movement of the arm will cause the rod or bar to twist the bar’s resistance to twisting provides a spring action. The torsion bar replaces both Coil spring and Leaf springs in some suspension systems. The main advantage of the torsion bar over the Coil spring in the Front suspension is the ease of adjusting front suspension height. Some are mounted longitudinally (i.e., front of car to back of car) or transversely (i.e., from the left side to right side of the car).

Torsion bar suspension
A Suspension system that makes use of torsion bars in place of the leaf or Coil spring.
Torsion damper
Torsion spring
Torsion strength
Torque is the force used in twisting, such as tightening a fastener. Torsion strength is the amount of force needed to twist a fastener apart. Both measures consider the amount of pressure applied to the fastener and the length of the wrench used in the application.
The inner surface of a hollow doughnut-shaped structure, especially found in automatic transmissions.

A special star-shaped screw recess or screw head top with six rounded corners to insert the tool. The TORX configuration on tools allows a very tight fit on the fastener and the application of high torque. The rounded corners also reduce wear of both the fastener and the tool
Abbreviation for Transmission Oil Temperature
Total Carbon
(TC) The sum of the elemental carbon and organic carbon associated with diesel particulates. Typically amounts to 80-85% of the total DPM mass.
Total energy management
Conservation concept where a building is looked at in terms of its total energy usage, rather than analyzing the requirements of separate systems.
Total harmonic distortion
(THD). The ratio of the root-mean-square (RMS) value of the sum of the squared individual harmonic amplitudes to the rms value of the fundamental frequency of a complete waveform.
Total heat
Sum of both the sensible and latent heat.
Total hydrocarbons
(THC) A measurement of all the hydrocarbons emitted by the exhaust system
Total indicator reading
(TIR) In disc brakes, this refers to a rotor runout reading of the entire swing of the dial indicator’s needle, both above and below zero.
A Car accident in which a vehicle has sustained severe damage so that the cost to repair it is more than what the vehicle is worth. In this case, it is Written off
Total loss
Ignition or lubrication system in which electricity or oil is used without being generated or recirculated. The ignition system uses power from a battery eventually running it flat. The lubrication system uses oil without returning it to a tank. Both systems were common on early motorcycles. Two-stroke engines use a total loss lubrication system. Scooters designed for the elderly or disabled use a total loss battery system because there is no alternator or generator to charge the battery as it is being driven
Total-loss lubrication
The components of the conventional two-stroke engine with crankcase scavenging are lubricated by the oil added to the fuel; since the oil is burnt along with the fuel, fresh oil is constantly fed to the lubrication points inside the engine
Totally enclosed
An electric motor housing that has no openings (but is not airtight). Used in locations where dirt, oil, etc. is present. It may be Fan-cooled or Convection cooled.
Totally enclosed fan-cooled enclosure
(TEFC) An electric motor housing that includes an integral fan to blow cooling air over the motor.

Totally enclosed non-ventilated enclosure
(TENV) An electric motor housing that is not equipped with a fan for external cooling, but depends on convection air for cooling
Total Out-Of-Pocket Cost
This is the total of all monthly payments, any lease fees and deposits, and any capital cost reduction (except tax, license, and registration) from lease inception to closure.
Total Particulate Matter
(TPM) The total particulate matter emissions including all fractions of diesel particulates, i.e. the carbonaceous, organic (SOF), and sulfate particulates.
Total quality management
(TQM) A management technique to improve the quality of goods and services, reduce operating costs and increase customer satisfaction.
Total Reflection
Total static head
Static head from the surface of the supply source to the free discharge surface.
Total Thread
Includes the complete or effective thread and the incomplete thread.
A power unit designed to transport mobile homes.
The condition after respraying a body when the paint coat has dried to an extent that foreign substances will not stick to the surfaces and light finger pressure will not leave any marks; the coat has not yet hardened completely, however, i.e., it cannot yet be sanded or polished
Touch up
To repair minimal blemishes in the paintwork, e.g., those caused by stone chippings or scratches
Toughened glass
Toughened windshield
A windshield made of toughened glass which, on impact, will not shatter like ordinary glass but fractures into small pieces and crazes over; laminated glass is now the preferred material
A fastener’s capacity to accept various impacts and shocks.
  1. British term for Touring car
  2. Similar to a Phaeton but the windshield does not fold, the posts are fixed. For example a 28-29 Ford Model A 4-door soft top is a tourer while the similar style for 30-31 is a Phaeton.
Touring bike
  1. A motorcycle that comes from the manufacturer with saddlebags and a trunk.
  2. A bicycle that has been equipped with saddlebags (often over the front wheels as well as the rear).
Touring car
A vehicle with a body longer than the phaeton style, but very similar to it. It permits the use of auxiliary seats in the rear passenger compartment. It was an open car with seats for four or more passengers. Early models had no side weather protection but later were fitted with detachable side screens and curtains. Made until about 1930.
Touring Prototype
Touring triple
A triple chainring crankset designed to provide the wide range of gears needed for loaded bicycle touring.
A cyclist who takes short or long excursions by bicycle often carrying several Panniers containing clothing and camping equipment.
An older and slower category Randonneur used in the 1901, 1911, and 1921 Paris-Brest-Paris events. In 1931 the race organizers turned this segment over to touring clubs.
  1. To pull a trailer behind a vehicle by means of a towing hitch.
  2. To pull a disabled vehicle behind another vehicle by means of a rope, cable or rigid bar
  1. A vehicle after an accident that is able to be towed.
  2. An old vehicle which may be used for parts or to be scrapped that is still able to be towed
This cargo category refers to motor vehicles being carried piggyback on a power unit. The trucks being carried have their front axles off the ground resting on the vehicle in front. Several vehicles may be hitched together in this way. This category is also used for wreckers towing a vehicle. Piggyback also refers to the way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road.
Tow away
To remove unauthorized (e.g., illegally parked) vehicles, thus incurring a hefty fine for the owners
Towaway cargo
The piggyback/towaway category refers to motor vehicles being carried piggyback on a power unit. The trucks being carried have their front axles off the ground resting on the vehicle in front. Several vehicles may be hitched together in this way. This category is also used for wreckers towing a vehicle. Piggyback also refers to the way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road. See also DECK SET.
Tow away zone
An area where unauthorized parking is not permitted. Unauthorized vehicles will be towed away
A British term for a Hitch ball
  1. A crossbar of a towing bracket on which the hitch ball is mounted.
  2. A rigid bar used for towing disabled vehicles short distances.
  3. A Drawbar
Tower jack
A tower with a solid foot and an arm at right angles which fits into a slot in the side of a car and is wound up the tower to raise the vehicle
Towing ball
A British term for a Hitch ball
Towing bracket
A structure attached to the rear of a car to enable a trailer to be towed. It consists of one or two brackets, a towbar and Hitch ball
Towing eye
A steel ring fitted to the chassis of a car to which a tow rope can be attached
Towing hitch
An inverted cup on the drawbar of a trailer which fits over a hitch ball
Towing hook
Towing jaws
A coupling attachment on the rear of a truck cab into which the drawbar eye of a trailer fits to lock with a coupling bolt
Towing lug
A steel ring fitted to the chassis of a car to which a tow rope can be attached
Towing package
Brand name for a fork lift
Town car
The same as the Imperial sedan without the rear quarter windows or a roof over the front compartment.
Town Coupe
See Coupe DeVille
Tow rating
The amount of weight in pounds of an external trailer that a vehicle can pull.
A rope, or textile-covered or plastic-covered cable, usually no longer than 5 metres, used for towing another vehicle
A substance which is poisonous to a living organism.
Toxic coolant
Transfer fluids having a Gosselin rating of two (2) or more, including ethylene glycol, hydrocarbon oils, ammonia refrigerants, and hydrazine. Such fluids are deemed essentially toxic by the BOCA Basic/National Plumbing Code.
Toxic Emission
Any pollutant emitted from a source that can negatively affect human health or the environment.
  1. The physiological effect of absorbing a poisonous substance into your body, either through the skin, through mucous membranes or into respiratory system. When describing their toxic effect, solvents are usually classified as having high, medium, or low toxicity, depending upon whether a solvent vapor concentration of less than 100, 100 to 400 or over 500 parts per million respectively is the maximum amount permissible in the air for safe or healthful working conditions.
  2. The relative degree of being poisonous or toxic. A condition which may exist in wastes and will inhibit or destroy the growth or function of certain organisms.
ToyotaClick image for books on

The largest car manufacturer in Japan and was until recently the third largest in the world (after GM and Ford), but has surpassed Ford in 2007. Includes 4Runner (1984-current), Avalon (1995-current), Camry (1980-current), Sienna (1998-current), Corolla (1966-current), Cressida (1973-92), Echo (2000-05), FJ Cruiser (2007-current), Highlander (2001-current), Land Cruiser (1951-2007), Matrix (2003-07), MR2 (1988-95), MR2 Spyder (2000-05), Paseo (1992-97), Pickup (1988-95), Previa (1991-97), Prius (2001-07), RAV4 (1996-current), Sequoia (2001-07), Sienna (1998-current), Solara (1999-2007), Supra (1979-2002), T100 (1993-98), Tacoma (1995-current),Tercel (1978-99), Tundra (2000-current), and Yaris (2007-current)

  1. Abbreviation for True Power
  2. Abbreviation for Throttle Position
Answer-Manitou suspension design that houses all damping in one stanchion, and a single spring in the other side.
Abbreviation for Tank Pressure Control Valve
Abbreviation for Tuned port injection
TP Mode
Abbreviation for Throttle Position Mode
Abbreviation for Tire Pressure Monitor System
  1. Abbreviation for Tread pattern percentage
  2. Abbreviation for Throttle Position Potentiometer
Abbreviation for Throttle position sensor — Detects location and speed of movement of accelerator
Abbreviation for Throttle Position Transducer (Chrysler)


Abbreviation for Total Quality Management.

  1. Abbreviation for Thermal reactor
  2. Abbreviation for Transmission Range Sensor Commonly called PRNGL – this provides input of the Gear Selector position
Tire and Rim Association.
  1. Front track is the distance between the center of the left front wheel and the center of the right front wheel when the vehicle is set to its normal ride height and wheel alignment specifications. Rear track is the distance between the center of the left rear wheel and the center of the right rear wheel. They are not always the same.
  2. A designated course or roadway where vehicles race.
Track arc
The path traveled by a road wheel during a turn
Track bar
Track bike
A type of bicycle used for racing on a bicycle track (velodrome); looks a lot like a road bike but features only one gear and has no brakes.
Track control arm
TrackerClick image for books on

A model of SUV produced by the Suzuki Motor Corporation and rebadged and sold through the Chevrolet division of General Motors from 1998 to 2004

  1. The alignment of the vehicle with respect to axle centers of a vehicle being in the same plane, rear tires following front tires and trailer following the tractor, in the attitude designed. Correct tracking is when the rear wheels of a vehicle follow the same line as the front wheels.
  2. A line of carbon along which electricity leaks.
  3. Shunt firing of a spark plug.
Tracking mark
A telltale sign on the distributor cover or ignition cables indicating a leakage of current
Tracking Switch
Track rod
One of the transverse bars connecting the steering system to the steering arms; the link between the pitman arm and the steering-knuckle arm.

  1. Pulling force.
  2. The force of adhesive friction exerted by a body on the surface on which it moves.
  3. Tires ability to grip the road. Higher traction allows greater braking and cornering force without slip, skid, or sinking.
Traction avant
A French term for Front-wheel drive
Traction bar
An Articulated bar or link attached to both frameRear axle housing to prevent Spring windup (with resultant wheel hop) during heavy acceleration or braking.

Traction control
  1. A system that helps prevent front-wheel spin on slippery or gravel surfaces during acceleration at speeds up to 40 kph (25 mph).
  2. A means of preventing wheelspin due to acceleration, either by braking the spinning wheel or reducing engine power.
Traction controls
The lever controlling the transfer gearbox and center differential lock.
Traction control system
Traction differential
Traction engine
A steam or diesel engine used for hauling heavy vehicles on roads or over difficult terrain.
Traction limited grade
Steepest negotiable grade where traction is the limiting factor.
Tractive conversion
Tractive effort
The amount of pull exerted by a vehicle as a result of traction.
The truck portion of semi-tractor-trailer unit or train which is designed to pull a semitrailer by means of a fifth wheel mounted over the rear axle(s). It has no cargo capacity. Unlike a straight truck which has a cargo body mounted to the truck frame, the tractor has a circular fifth wheel plate for coupling to a semitrailer. A tractor may includes gooseneck hitch tractors, even though they lack fifth wheels; and includes auto carrier tractors with racks for carrying automobiles; includes mobile home haulers. Tractors can carry motor vehicles in a saddlemount or piggyback fashion. Sometimes called a truck tractor or highway tractor to differentiate from it from a Farm tractor.

A Tractor and Semi-trailer combination.
Trade agreement
Trade Agreement of the Americas
Trade-in price
The price of your old car when you are selling it in part exchange for another one
Trade Organization
A road with moving vehicles.

Traffic circle
An intersection of several roads where the traffic goes around a central circle and goes out another road. Although it is a rapid way of negotiating an intersection, many people are intimidated by it because of its unfamiliarity. The British term is roundabout
Traffic control devices
Signs, signals, markings, and other devices placed on or adjacent to a road to regulate, warn or guide traffic.
Traffic control measures
Elements of the traffic control plan including, but not limited to, traffic control devices, personnel, materials and equipment used to control traffic through a work zone.
Traffic control plan
A written and drawn plan for handling traffic on a specific roadway through a work zone.
Traffic Counters
Traffic island
A raised area in the middle of a road designed to separate two flows of traffic and to provide a safe temporary stopping place for pedestrians crossing the road
Traffic jam
A number of vehicles stopped behind one another on a road
Traffic lane
That part of the road marked for moving a single line of vehicles.
Traffic light
A series of red, amber, and green lights placed at the intersection to regulate the flow of traffic
Traffic Safety Administration
  1. A path used by pedestrians and smaller vehicles (e.g., bicycles, quads, snowmobiles, etc.).
  2. The path that a wheel makes.
Trail bike
A dual purpose motorcycle for use on or off-road
TrailblazerClick image for books on

A model of full-size SUV-van produced by the Chevrolet division of General Motors from 2002 to 2008

Trail braking
A driving technique in which the driver begins to brake before entering a turn and then continues to brake as he eases into the corner. As cornering forces build, the driver gradually feathers off the brakes — trading braking power for cornering grip. By increasing the vertical loading — and thus the traction — at the front tires, trail-braking can improve a car’s turn-in.
Trail distance
The distance from the point at which the cornering force acts to the center of the wheel or Steering axis.
  1. Platform or container on wheels pulled by a truck or tractor.
  2. Distance between fifth wheel pin and center of rear axle (or center between tandems).
  3. A unit which contains camping equipment and is pulled behind a vehicle.
Trailer Kingpin
An anchor pin at the center of a semitrailer’s upper coupler which is captured by the locking jaws of a tractor’s fifth wheel to attach the tractor to the semitrailer.
Trailer On Flatcar
(TOFC) A method for moving cargo which involves transporting semitrailers on railroad flatcars.

Trailer preponderance
A condition where there is a heavier load on the front of the trailer (thus on the vehicle towing hitch) than on the back of the trailer.
Trailer tire
A small tire often 12′ with a load range B and a capacity rating of 850 lbs
Trailer towing package
Trailer-towing package
An Optional equipment which usually includes a heavy-duty suspension a larger radiator a transmissionCooler and a rear bumper with a trailer hitch. This improves handling and allows a vehicle to haul a heavy trailer.
Trailer weight
Trailing arm
Trailing armTrailing arm

Type of Independent rear suspension in which the pivot axis is exactly across the vehicle, or perpendicular to the longitudinal axis. This means the wheels are always upright relative to the body and hence leaning with the body in a corner. Widely used at the rear of front-wheel-drive cars.

Trailing axle
Trailing brake shoe
The brake shoe that is installed facing the rear of the vehicle. Also called Secondary brake shoe or Reverse brake shoe.
Trailing edge
The rear edge (e.g., of a body panel). Compare Leading edge
Trailing link
A front suspension linkage that is aligned to resist longitudinal motions in a wheel; it is mounted to the chassis ahead of the wheel. The links pivot forward of the axle.

Trailing link suspension
Trailing shoe
  1. A shoe whose friction surface trails behind the shoe pivot and is pushed away from the drum by drum rotation.
  2. A British term for a Secondary shoe — a shoe of a brake drum system whose activated end faces away from the approaching drum
Trailing throttle
An oversteer handling situation of rear drive cars. When the throttle is closed the engine applies compression braking so that the rear suspension alignment changes. This change causes the rear tires to lose traction which promotes a lateral slide.
Train station
Trucker slang for Traffic court that fines everyone as in ‘Get out your money traffic court is a real train station today.’
Train Stop
Train weight
  1. A British term for a Streetcar.
  2. A small train used to haul ore at a smelter.
A British term for a Streetcar
Tram gauge
An alignment tool — a long bar that has two or three parallel pointers extending at right angles and attached so that they can be moved to any position along its length
The rails along which a tram runs
The tendency of a vehicle’s tires (often when of low profile) to follow a ridge or rut in the road’s surface
  1. A hopping or oscillating motion of the front wheels usually caused by incorrect balance or when a high inflation tire has been run empty.
  2. The action of rapidly depressing the throttle pedal.
The rails along which a tram runs
Colloquial name for transmission.
Abbreviation for transmission.
Trans Am
Trans AmClick image for books on
Trans Am

A sports car manufactured by the Pontiac division of General Motors

A drive setup in which the transmission Gearbox, clutch, final drive, and differential are combined into a single unit connected directly to the driveshaft. It is used mostly in rear-engine cars like the Corvair or Front-wheel drive cars and some performance cars where a front engine/rear transaxle gives better overall balance (such as the Alfa Romeo Alfetta).

Trans-Canada Highway sign
Trans-Canada Highway
One of the world’s longest national highway of 8,030 km (4,990 mi). The highway system is recognizable by its distinctive route marker displaying a white maple leaf on a green background. A number 1 (for the southern route) or 16 (for the Yellowhead route) appears in the middle of the maple leaf. Below the maple leaf is the name of the province.
A radio device which can transmit a signal and opposite to a receiver
  1. A device for transferring power which is generated in one system to another system in the same or a different form, e.g., electrical to mechanical.
  2. Any device that converts an input signal into an output signal. Used to actuate electric or vacuum servo motors in an automatic temperature control system.
  3. Device turned on by change of power from one source for purpose of supplying power in another form to second system.
Transducer Assembly
Transducer EGR
Transducer EGR valve
Transducer Valve
A process in which organically-derived oils or fats are combined with alcohol (ethanol or methanol) in the presence of a catalyst to form esters (ethyl or methyl ester).
Transfer box
A device that transfers power from the main gearbox (transmission) to both the front axle and the rear axle on a four-wheel drive vehicle.

Transfer case
An auxiliary device in a 4-wheel-drive vehicle that allows power to be delivered to both axles. Normally the transfer case incorporates a shifting device so that the front drive can be disconnected, if desired, for running on pavement. It is mounted between the transmission and driveshaft.

Transfer Dump
A straight dump truck pulling a full dump trailer without hydraulics. The dump box of the trailer slides (transfers) into the empty dump bed of the power unit using the hydraulics of the power unit to unload.
Transfer Effect
Transfer Gear Lever
The small gear lever in the cab next to the main gear lever. It controls whether the transmission is in high ratio or low ratio in the transfer box. The same lever also controls the engagement of the differential lock.
Transfer Module
Transfer molding
The development of Compression molding where powder polymer is placed in a small chamber adjacent to a tool mold and when heated, is forced into the tool cavity.


Transfer moulding
British term for Transfer molding
Transfer passage
The passage connecting the crankcase of a two-stroke engine with the combustion chamber
Transfer plate
An adapter plate in the control valve assembly of an automatic transmission, used to direct the fluid flow between adjacent valve bodies
Transfer port
A channel in the block of a two-stroke engine where the air-fuel mixture enters the combustion chamber and exits out another transfer port after it burns.

Transfer port cover
The transfer passages of most two-stroke engines are accessible from the outside to allow for maintenance, they are covered by the transfer port covers for regular engine operation
Transfer ports
The holes that deliver fuel from the idle circuit during the transition from curb-idle to the main metering circuit. Located just above the throttle plates. At curb idle, off-idle ports function as an extra air bleed for further emulsification of the idle mixture; but as vacuum moves up the carburetor bore when the throttle plates are opened, they become fuel discharge ports. Either one or more holes, or a single slot (slots are usually used because they are cheaper to manufacture). Also called Off-idle discharge ports
Transfer pump
  1. An in-tank pump, used on many Bosch and some other fuel injection system, that boosts the fuel pressure slightly before the fuel is sucked into the main pump, in order to prevent cavitation. Also, part of the fuel injection pump for a diesel engine, boosts fuel pressure from around 20 psi to about 130 psi, depending on the pump and the engine speed
  2. Fuel pump located in the fuel tank, usually used with a two pump system
Transfer Slot
  1. An electrical device with an arrangement of copper coils with an iron center, used to increase or decrease electrical voltage. A vehicle ignition coil transforms the voltage from 12 volts to upward of 20,000 volts.
  2. Electromagnetic device which transfers electrical energy from primary circuit into variations of voltage in secondary circuit.
Combination transformer and rectifier in which input ac current may be varied and then rectified into DC current.
Transient speed changes
See Momentary speed changes
  1. Electronic device commonly used for amplification. Similar in use to electron tube. Depends on conducting properties of semiconductors in which electrons moving in one direction are considered as leaving holes that serve as carriers of positive electricity in opposite direction.
  2. A small semi-conductor electronic component, with at least three connections but no moving parts, that functions as a switch, amplifier, or detector by controlling the flow of current.
Transistor ignition
A form of ignition system which uses transistors and a special coil. The conventional distributor and point setup is used, but the points merely serve to trigger a transistor which switches the heavy primary current. With the transistor unit, the voltage remains constant, thus permitting high engine rpm without resultant engine miss. Transistors are much more efficient switches at high engine speeds and in addition they don’t burn, pit or change gap spacing. The advantages of these systems include greatly increased point life, generally better starting because of improved contact condition and voltage output not greatly affected by Breaker pointDwell time which results in better high-rpm performance. Also point life is greatly extended as the transistor system passes a very small amount of current through the points.
Transistorized coil ignition

Transistorized coil ignition with Hall sensor

Transistorized ignition
(TI) An ignition system using a transistor as a power switch; available as breaker-triggered TI with contact breaker or as breakerless TI with magnetic pick-up or hall generator.

Transistorized ignition with inductive pulse generator
Transistorized ignition with Hall generator
(TI-H) There are two types of TI-H in one version, the dwell angle is determined by the width of the rotor vanes in the distributor; the other version contains a circuit for automatic dwell angle control incorporated in the electronic control unit
Transistorized ignition with inductive pick-up
(TI-I) A transistorized ignition system with a magnetic pick-up in the distributor and an electronic control unit for signal processing, with current and dwell angle control
Transistorized ignition with magnetic pick-up
(TI-I) A transistorized ignition system with a magnetic pick-up in the distributor and an electronic control unit for signal processing, with current and dwell angle control
Transit Bus
A bus providing passenger transportation over fixed scheduled routes within primarily urban geographical areas.
Transitional Low-Emission Vehicle
(TLEV) A vehicle meeting either EPA’s CFV TLEV standards or CARB’s TLEV standards. TLEVs produce fewer emissions than federal Tier 1 vehicles. TLEVs are eligible for the federal California Pilot Program but not eligible for the Clean-Fuel Fleet Program. The TLEV standards are less stringent than the LEV standards.
Transit system
  1. A component of gear that allow your car to move forward and backward with varying amounts of power to meet a variety of driving situations. Manual transmissions are operated by means of a clutch and gearshift. Automatic transmissions are driven by hydraulic pressure.
  2. A device (full of gears) that uses Gearing or Torque conversion to effect a change in the ratio between engine rpm and driving wheel rpm. When engine rpm goes up in relation to wheel rpm, more torque but less speed is produced. A reduction in engine rpm in relation to wheel rpm produces a higher road speed but delivers less torque to the driving wheels.
  3. Heat loss or gain from a building through exterior components such as windows, walls, floors, etc.
Transmission adapter
A unit that allows a different make or year transmission to be bolted up to the original engine.
Transmission, automatic
Transmission brake
The handbrake on all Land Rovers operates by gripping the rear propeller shaft at the point where it leaves the transfer gearbox and is thus called a transmission brake. It should be used as a parking brake only and should never be operated whilst the vehicle is in motion except in emergency –
Transmission control
Transmission controlled spark
(TCS) A system to reduce the emission of nitrous oxides by which a vacuum solenoid and a switch in the transmission system prevents the distributor’s vacuum advance mechanism from operating in the lower gears and at low speed
Transmission control module
(TCM) An electronic automatic transmission control unit which computes data on the actual operating conditions of the vehicle and generates corresponding signal pulses for the solenoid valves of the hydraulic control system; may also exchange data with other electronic control units
Transmission control system
A hydraulic or electro-hydraulic system which controls the changes of ratio in automatic transmissions corresponding to engine load, vehicle speed, positions of the selector lever, and shift mode button
Transmission, conventional
Transmission cover
A removable part of the floorpan usually located at the front end of the center tunnel in cars with a longitudinally mounted engine; provides better access to the top of the transmission for maintenance and adjustment purposes
Transmission extension housing
A rear-wheel drive transmission housing enclosing an extended main shaft, sometimes accommodating the gear lever and associated mechanism
Transmission fluid
(ATF) A superthin oil that fills the automatic transmission system so that it can run on hydraulic pressure. It can also be used in some power-steering pumps. It is sometimes used to clean the inside of a carburetor.

Transmission governor
A governor on the output shaft of a hydraulically controlled transmission converts line pressure into governor pressure. In electro-hydraulically controlled transmissions, the governor is replaced by a sensor.
Transmission housing
The outer shell which contains the transmission gears.
Transmission input shaft
A spinning shaft which transmits power from the clutch to the gearbox
Transmission output shaft
A spinning shaft which transmits the power out of the transmission
Transmission powertrain control module
An electronic module or a computer that receives input from various transmission related sensors to determine the operating condition of the transmission at a particular moment. The transmission module or computer responds to these signals and/or input from the PCME by sending signals to various transmission controls to meet predetermined operating instructions.
Transmission shifter
Transmission tunnel
A semicircular or oval bulge along the longitudinal axis of the floorpan to accommodate the propeller shaft and, at its front end, the transmission, enabling the shaft and transmission mounting position to be raised to the floorpan level, thus providing better protection for the drive train against road dirt and obstacles
Transmission wind-up
A 4×4 with no center differential or one driven with the center differential locked (i.e., in both cases the front and rear propeller shafts locked together) is unable to accommodate the small differences in distance normally traveled by the front wheels compared to the rear wheels. The differential lock ensures both propeller shafts rotate exactly the same amount despite the small differences in distance actually traveled. This results in some wheel slip and skid which, on loose ground, can take place without any harm. On hard roads, however, the superior wheel grip makes it difficult for the wheels to slip much and in the process of trying to do so considerable torsional stress builds up in the transmission. This is known as transmission wind-up and can sometimes exert so much stress that the differential lock gears will not disengage when so selected. You will also sense very heavy steering. If this occurs due to your forgetting to de-select differential lock on hard ground (or at any other time) and the differential lock will not disengage, the solution is to reverse the vehicle some distance until the differential lock warning light goes out.
A radio remote control system device that transmits electrical or radio signals.

Transmitting Valve
A horizontal bar or beam
Transom beam
The aftermost transverse deck beam
Transom frame
The aftermost transverse side frame
Transom stern
A square-ended stern used to provide additional hull volume and deck space aft and to decrease resistance in some high speed ships.
An overseas production plant; in most cases, the term refers to automotive vehicles produced in the USA, Canada, or Europe at Japanese-owned factories (e.g., a Toyota plant in Cambridge, Ontario, Canada)
A means of carrying goods or people by light duty vehicles, busses, heavy-duty vehicles, and off-road vehicles.

Transportation Research Board
(TRB) Serves as an independent adviser to the U.S. federal government and others on scientific and technical questions of national importance. Promotes innovation and progress in transportation through research; stimulates research and offers research management services that promote technical excellence; provides advice on policy and programs.
Transportation Safety Board
Transportation sector
An energy-consuming sector that consists of all vehicles whose primary purpose is transporting people and/or goods from one physical location to another. Included are automobiles; trucks; buses; motorcycles; trains, subways, and other rail vehicles; aircraft; and ships, barges, and other waterborne vehicles. Vehicles whose primary purpose is not transportation (e.g., construction cranes and bulldozers, farming vehicles, and warehouse tractors and forklifts) are classified in the sector of their primary use. Note: Various EIA programs differ in sectoral coverage. Click here for an explanation of the variations of the transportation sector used by EIA system(s).
Transportation Systems
A large articulated truck for transporting several cars (on two or three decks)
Transverse arm
A suspension arm not split into two separate sections as is an A-arm. Often used as the bottom locating link with MacPherson strut suspension. Also called lateral arm.

Transverse cable
Transverse engine
An engine that is mounted laterally (i.e., left to right) between the drive wheels (rather than longitudinally — front to back), often found on cars with Front-wheel drive. Also called east-west layout
Transverse flow scavenging
Transverse leaf spring
A Leaf spring that is mounted so that it is at right angles to the length of the vehicle.
Transverse link
Any suspension link that provides lateral support for wheels; on front suspensions, a typical design is the Y-shaped wishbone
Transverse mount
The engine is mounted sideways. The fan belt will be over one of the tires rather than in the very front of the vehicle. This is common in front-wheel-drive cars. This enables the car to be more compact because the space under the hood is used more efficiently and provides better weight distribution.

Transverse rod
Transverse torsion bar
  1. The area over which the vehicle is raced for timing purposes.
  2. A filter or separator
  3. A pedal on a bicycle into which the foot is locked in place.
Trap oxidizer
In diesel particulate filters, a means of burning the particulate charge trapped in the filter element, to prevent the filter from clogging and to restore filtration capacity; usually a catalyst coating that promotes oxidation of carbon particulates to harmless carbon dioxide
Trapped volume
A Clearance volume
Trapping efficiency
In a two-stroke engine, the mass of fresh charge in a cylinder actually retained, divided by the mass of fresh charge supplied per cycle
Trauma fee
$6 per $1000 of car value levied annually in Washington State (and others) to support trauma units in hospitals that care predominantly for car crash victims.
  1. The distance an object can move.
  2. The distance that suspension components, forks and shocks, move up and down when the bike rides over bumps.
  3. Measurement of the total distance that a shock can move.
Travel trailer
Travel TrailerTravel Trailer

A recreational unit which is pulled behind a vehicle and has similar amenities that are featured on a Class A RV. Some have slideout sections to extend the living space. They can sleep up to eight people. They feature a small bedroom, bathroom (toilet, shower), fully equipped galley (cooking facilities, refrigerator, sink, faucets), water tanks (fresh water, grey water, black water), heater, air conditioner, a LP (propane) gas supply, and a separate 100-125 volt electrical system Most tow vehicles must be equipped with a load distributing hitch and other special devices designed to control the sway of the trailer.

travel trailerClick image to supersize
travel trailer

  • Average weight under 4000 pounds
  • Average length 10 ft to 35 ft
  • Average price $10,000 to $100,000
Tray table
A table that folds out of the back of the front seat (similar to those found on airplanes)
Abbreviation for Transportation Research Board which serves as an independent adviser to the U.S. federal government and others on scientific and technical questions of national importance. Promotes innovation and progress in transportation through research; stimulates research and offers research management services that promote technical excellence; provides advice on policy and programs.
TR-Denioc rim

TR-Denioc wheel
  1. The distance between the two front or two rear wheels.
  2. Portion of the tire which contacts the roadway.
  3. The grooves on a tire which provide a grip on the road
  4. The pattern of the outside circumference surface of a tire.
  5. Load-bearing surface of a trail or road.
Tread bar
Raised portions of rubber that make up me tread of the tire, separated by grooves that are arranged laterally, providing traction in the forward or rearward direction.
Tread block
Raised portions of rubber that make up part of the tread pattern They are often present in the shoulder area and are more or less rectangular in shape.
Tread depth
The measurement from the bottom cm of the tread groove to the top of the tread expressed in millimetres or 32nds of an inch. The legal minimum amount of tread is 1.6 mm (2/32′) across three-quarters of the tire width
Tread depth gauge
A simple compact device for measuring the depth of tread, consisting of a spring-loaded plunger calibrated in millimetres or 1/32 of an inch
Tread gauge
Tread groove
One of several channels cut in the tread that disperses road water or provides traction in mud and snow
Tread pattern
Tread patterns differ according to the manufacturer of the tire but they all have in common the aim of dispersing water from the road, to enhance grip, to avoid aquaplaning, to disperse heat, and to reduce noise and wear
Tread pattern percentage
(TPP) The percentage of grooves and sipes to the overall surface of the tread
Tread profile
The shape of the tread as seen in cross section
Tread rib
The continuous raised portions of rubber that run circumferentially (straight or in a zigzag pattern) making up the tread on the tire. Also called the Tread bar
Tread roller
A roller, either manual or power, used to help apply me tread rubber, remove trapped air and obtain adhesion.


Tread rubber
Tread separation
Pulling away of the tread from the Tire casing.
Tread squirm
The flexibility in the Tire tread between the surface of the tread and the tire carcass. Snow tires, with their small, deep, unsupported tread blocks, have a large amount of tread squirm. Slick racing tires, which have no tread pattern, have very little squirm.
Tread wear indicator
Tread-wear indicator
Tread wear indicators
Tread-wear indicators
Bars of hard rubber that appear across the treads of a tire. They are 1.5 mm (1/16′) above the base of the tread (the legal limit. They become visible when the tread has been worn down so that only 1.5 mm (a sixteenth of an inch) of tread is left. The legal limit may be shown on the sidewall by a symbol or by the letters TWI
Three-lead semiconductor that allows current flow in two directions when a preset voltage is applied at one of the leads.
A type of ATB bicycle or off-road motorcycle competition that tests riders not on speed but on ability to maintain balance while navigating around and over numerous obstacles such as rocks, trees, and steep, slippery terrain. Points are deducted if the rider puts his feet on the ground, goes outside the marked course, or fails to clear an obstacle.

Triangle split system
Dual brakesDual brakes

A brake system that uses a tandem or dual master cylinder to provide separate brake system for both front and rear of vehicle. In the event of a loss of hydraulic fluid, one system may still work because it is independent of the other system. Some cars like the Rolls-Royce, link the two front brakes with the right rear brake, and the two front brakes with the left rear brake.

Triangle-split system
Triangular ground electrode
A ground electrode with three bridges attached to its end points, which form a link to the threaded shell
Triangular safety reflector
The arrangement of the stabilizing tread plies whereby their cords form tiny triangles in the Michelin ‘X. radial truck tire.
A competition in which the participant must swim, cycle, and run a designated distance in each discipline.
Triathlon tire
Triathlon bicycle tires are usually 650c. Although they are sometimes referred to as 26 inch, they are not compatible with tires meant to fit ATB rims.
Triathlon wheel
A wheel consists of a hub, rim, and spokes. Triathletes often prefer to use smaller size wheels than road riders. Triathlon specific wheels are size 650C.
  1. A truck, tractor, or trailer with three axles grouped together at the rear.
  2. Normally implies four total axles if used to refer to a straight truck.

Tri bars
An old name for a three-wheeler
(C2HCl3) A cleaning solvent Methyl chloroform
(C2HCl3) A cleaning solvent
Complete name of refrigerant R-1 13. Group 1 refrigerant in rather common use. Chemical compounds which make up this refrigerant are chlorine, fluorine, and ethane.
  1. A description of a whole motorcycle which is really cool, really hot, really new and unobtainable or expensive.
  2. A component of a motorcycle which is unique
Trickle charge
A continuous charging of a storage battery at a low rate to keep it in a fully charged condition for a period when no current is drawn from it
Trickle charger
A small battery charger which delivers less than five amperes
A three wheeled vehicle (usually pedal-powered) where there is a single front wheel and two rear wheels. A three-wheeled, early-type open automobile using bicycle wheels and a steel-tube frame.


A group of three axles on a truck, tractor, or trailer. Tridems are most common on European semi-trailers.
A vehicle having three rear driving axles.
An implement used in testing something such as the variation from level (e.g., Bubble Trier)
A stretchable laminate of Polartec Fleece and Nylon/Lycra. Windproof, waterproof and breathable. Triflex creates the warmest cold weather cycling gear.
Trigger box
Triggering device
An electronic control unit that activates the air bag in a crash. It contains a deceleration sensor, a Hamlin switch and a check circuit
Triggering mechanism
A device that controls the timing of the ignition module or ignition coils on vehicles with electronic ignition systems.
Triggering unit
An electronic control unit that activates the air bag in a crash. It contains a deceleration sensor, a Hamlin switch and a check circuit
Trigger wheel
  1. A rotor of a magnetic pick-up integrated into the distributor, with as many teeth as the engine has cylinders.
  2. A Hall generator rotor with an outer ring interrupted by one or several Hall windows, depending on its purpose
  3. A Reluctor
A Tricycle. A motorcycle that has been converted to a three-wheeled unit. Sometimes the rear two wheels are powered by a small automobile engine.
  1. Nonfunctional metal or plastic molding, frames and other decorative additions to vehicle bodies and interiors. Also called Hard trim.
  2. A vehicle’s interior decoration, including the upholstery, roof and door linings. Also called Soft trim.
  3. The difference between the draft forward and the draft aft. A ship is trimmed by adjusting the location of fuel, cargo, ballast, etc.
A triple hulled vessel
Trim Buck
A temporary adjustable items within the passenger compartment of a vehicle. It is used in the manufacturing stage to determine the best size and placement of the controls, guages, instrument panel, etc.
Trim emblem
Trim Heads
Similar to the 82 degree flat and oval head machine screws except that the size of head for a given size screw is one or two sizes smaller than the regular flat and oval sizes.
Trim level
A vehicle designation assigned by vehicle manufacturers that represent specific equipment packages.
Trim Pad
Trim panel
The decorative interior panel
Trim panel release tool
A fork-like tool used to pry out fasteners on interior panels without breaking them or damaging the car
Trim rim
Tri-oval track
An oval track with an extra rounded corner. Daytona is a tri-oval track.
  1. In the OBD system, a journey during which all OBD tests have been completed.
  2. Abbreviation for The Road Information Project — a nonprofit organization that promotes transportation policies that relieve traffic congestion, improve air quality, make highway travel safer and enhance economic productivity.
Trip Charter
A hiring vessel to haul cargo for special voyage.
Trip computer
A computer with a multifunction display; supplies the driver with trip information such as range, ETA, distance to destination, time, fuel economy, fuel consumption, average speed, accumulated trip miles, elapsed time since last reset
Tri pin
Tri pinTri pin

A device which is attached to a steering wheel to allow disabled people to insert a hand into its bracket in order to steer a vehicle.

Trip Leasing
Leasing a company’s vehicle to another transportation provider for a single trip.
Triple clamp
The devices which secure the handlebar to the Triple tree on a motorcycle. Named because is has three clamping points — one for each of the two front forks, and one for the steering tube.
Triple crank
A crankset with three chainrings designed to provide a wide range of gears and gear intervals
Triple point
Pressure-temperature condition in which a substance is in equilibrium (balance) in solid, liquid, and vapor states.
Triple tree
The yoke that supports the handlebar on a motorcycle.
Triplex chain
A chain with three rows of rollers.

Trip meter
An instrument which measures the distance a vehicle travels from the last time it was reset and runs in conjunction with the odometer
Trip mileage counter
An instrument which measures the distance a vehicle travels from the last time it was reset and runs in conjunction with the odometer
Tripod jack
A device for lifting a vehicle.
Tripod joint
A constant velocity joint with three balls engaged in curved grooves
Trip odometer
An auxiliary Odometer that may be reset to zero at the option of the driver. It is used for keeping track of the mileage on trips up to one thousand miles.
Tripping bracket
Flat bars or plates fitted at various points on deck girders, stiffeners, or beams as reinforcements to prevent their free flanges from tripping
Trip recorder
  1. Incorporated in the speedometer, the trip recorder indicates the distance (in miles or km) covered during a particular journey (trip), either mechanically or electronically; trip figures can be reset to zero by turning or pushing a reset button. Also called a Trip meter, Trip mileage counter, or Trip odometer
  2. A cab-mounted device which electronically or mechanically records data such as truck speed, engine rpm, idle time and other information useful to trucking management.
TriumphClick image for books on

A vehicle brand of motorcycles and automobiles of which the following car models are classic cars:

  • Dolomite 8
  • Gloria 6

The 1953-63 TR2/TR3 models are milestone cars.

Abbreviation for Thermal Vacuum Valve
TR number
Code number of the tube valves and flaps set by Tire and Rim Association.
Trolley busTrolley bus

An electrically powered public transport bus that takes its power from overhead wires

Trolley jack
A hydraulic jack with swivel wheels
Trolley Reverser
Part of the atmosphere immediately above the earth’s surface in which most weather disturbances occur.
Tropospheric ozone
(smog) is formed when volatile organic compounds (VOCs), oxygen and NOx react in the presence of sunlight (not to be confused with stratospheric ozone, which is found in the upper atmosphere and protects the earth from the sun’s ultraviolet rays). Though beneficial in the upper atmosphere, at ground level, ozone is a respiratory irritant and considered a pollutant.
Trouble code
  1. Engine self diagnosis. Electronic control module questions sensor reading and stores code for which circuit trouble is located
  2. Numerical codes created y an electronic module with self-diagnostic capabilities and normally stored in the module memory. They result from a system self-test that indicates a circuit or subsystem problem, or a general condition that is not within limits. Often called fault or service codes, they are now referred to as diagnostic trouble codes.
Diagnosing engine, transmission etc., problems by various tests and observations.
Trouble-shooting light
A light with a long lead, used in garages to inspect the underside of cars and under the hood
High-temperature (180+) concentrator with one axis-tracking.

Troy weight
A system of measurement of weight used for gold, silver, and platinum
Troy ounce
A measurement of weight where one troy ounce equals 31.10 grams. In writing, it is often shortened to troy oz. after figures, e.g., 25.2 troy oz. Troy weight is divided into grains, pennyweights (24 grains = 1 pennyweight), ounces (20 pennyweights = 1 ounce) and pounds (12 troy ounces = 1 pound). Troy weights are slightly less than their avoirdupois equivalents; the troy pound equals 0.37 kg or 0.82 lb avoirdupois
TR rim
A safety rim developed by Michelin with a flattened rim flange and run-flat potential
Abbreviation for Transmission Regulated Spark Control System
Abbreviation for Transmission Regulated Spark Control System
TRUARC® retaining ring
A trade name for an internal or external circlip of rectangular cross section with holes for easier installation and removal.
  1. A general term for a vehicle designed to haul something. The British term is lorry.
  2. Vehicle which carries cargo in a body mounted to its chassis, rather than on a trailer towed by the vehicle.
Truck camper
Truck camperTruck camper

A vacation unit which mounts on the bed of a pickup truck. Also called pickup camper, or slide-on camper, slide-in camper, or simply camper. Usually the tailgate of the pickup is removed and the camper unit is clamped to the truck. It provides as much as cooking facilities, a refrigerator, heater, air conditioner, a self-contained toilet, a fresh water tank, a waste water tank, a faucet, a sink, a LP (propane) gas supply, and a separate 100-125 volt electrical system. They can sleep from two to six people. Prices range from $5,000 to $30,000. Its advantage is that the vehicle can be used to drive into remote locations.

Truck classification
Vehicle classifications for automobiles and light duty trucks were obtained from the EPA mileage guide book. Almost every year there are small changes in the classifications, therefore the categories will change accordingly. The EPA mileage guide can be found at any new car dealership.
A person who drives a large truck (i.e., larger than a pickup) — usually one who drives a semi-tractor

Trucker slang
A colloquial set of expressions used on a CB communication device.
Truck Ramp
Truck Tractor
The truck portion of semi-tractor-trailer unit or train which is designed to pull a semitrailer by means of a fifth wheel mounted over the rear axle(s). Also called a highway tractor
Truck-type switchgear
A switchgear mounted on a platform with wheels
  1. Something that is accurately made or correctly adjusted.
  2. To adjust something so that it is able to fit perfectly.
True and Level Paving
(T&L) The roadway is paved with asphalt concrete to raise up the low spots and re-establish a proper ‘crown’ for the road. This promotes good drainage of water off the road and improves the smoothness of ride quality. The final treatment may actually skim over some areas that will show little to no new asphalt, while other areas receive a couple inches of new asphalt. This work may take several days, and is usually followed by the application of a surface treatment.
True Paving
True up
To Dress
  1. The act of cutting rubber off the tread of a tire while rotating on a truing machine to make the tire assembly round. A sometimes harmful practice which takes off tread rubber to allow for an out of round wheel, or for a tire not mounted properly.
  2. Process of adjusting a spoked wheel to correct for lateral and radial runout esp. after lacing.
Truncation of Thread
A British term for kingpin — a mechanical pivot located at the lower end of the suspension wheel upright.
The storage compartment of a vehicle. In older cars, a large suitcase (or trunk) was strapped to the back of the vehicle. In rear-engine vehicles, the trunk is located in the front of the vehicle (e.g., Volkswagen); but generally it is located at the rear of the vehicle.

Trunk handle
A lever or handle for opening the trunk
Trunk-piston type
A piston that is connected to the upper end of the connecting rod directly. Indirect connection is called crosshead-piston type.
Trunk lid
The cover of the trunk which is hinged
Trunk model
A vehicle which may come as a hatchback or stationwagon is available in a style which has a trunk behind and below the backlight (i.e., rear window).
Trunk rack
  1. A luggage rack which is mounted to the surface of the trunk. Some are merely decorative.
  2. A bicycle carrying attachment mounted by straps to the rear of a car or truck. Less expensive than most roof or hitch racks.
Trunk spoiler
A Rear spoiler which is mounted to the lid of the trunk.
A supporting framework for a bridge
Truss Head
Low rounded top surface with a flat bearing surface.
Abbreviation for Technical Service Bulletin

A variation of the Split skirt piston. The top of the T tends to retard the transfer of heat from the head to the skirt of the piston. The vertical slot allows the skirt of the piston to close when heated.

Abbreviation for Throttle Solenoid Positioner (Ford)
  1. Abbreviation for Transmission Shaft Speed Sensor
  2. Abbreviation for Turbine Speed Shaft Sensor Measures turbine speed to aid controlled slip
TSXClick logo for books on

A model of automobile from Acura


  1. Tourist Trophy races held on the Isle of Man
  2. Abbreviation for Time trial, a competition where a vehicle seeks to cover a certain distance in the best time possible. In most cases the vehicle proceeds solo (i.e., other vehicles are not on the track at the same time)
  1. A long, narrow, hollow cylinder for holding or passing liquids or gases.
  2. A rubber doughnut-shaped bladder which is placed within the carcass of a tire and inflated.
  3. A light tube, fluorescent tube
Tube axle
Tube bender
A tool for bending tubing without collapsing it
Tube, constricted
Tubing reduced in diameter.
Tube butyl
Tube cutter
A tool used to cut tubing by passing a sharp wheel around and around the tube.

A tire which has an inner tube
Tube drive
Tube frame
A car frame made up of rigid tubing welded together. Tube frames are easier to manufacture in small quantities than unitized frames.
Tube latex
A tire with no inner tube
Tubeless tire
A tire which does not have a tube. Air is sealed in the tire chamber because the bead of the tire adheres to the tire’s rim. First developed by B. F. Goodrich in 1948.
Tubeless tires
Tube Refrigeration
Tube seat
An insert or machined face, against which a flared tube end seals.
Tube Shifter
Tube System
Tube Trailer
A semitrailer used to transport cryogenic gases.
Water-cooled condensing unit in which a small tube is placed inside large unit. Refrigerant passes through outer tube, water through the inner tube.
  1. Fluid-carrying pipe which has a thin wall.
  2. Semi-rigid conduit of steel, copper, aluminum, or plastic.
Tubing bender
A tool used to bend tubing without kinking or deforming its walls.
Tubing reamer
A tool used to remove burrs on hard tubes (not inner tubes), e.g., after a tube cutter is used when servicing the brake line system
Tubing wrench
A wrench used to turn fittings on tubing. A tubing wrench distributes the turning forces evenly around the fitting and minimizes the possibility of damage.
In the shape of a tube; cylindrical
Tubular backbone frame
A backbone chassis with a tubular central spine
Tubular cells
Fuel Cells that are formed in cylindrical fashion and allow fuel and oxidant to flow on the inner or outer surfaces of the pipe.
Tubular frame
A frame construction that features members of tubular cross section; often used for racing cars, as this layout allows for weight-saving design with the use of aluminum
Tubular nut driver
A nut driver with handle and tubular shank for driving hexagon nuts and bolts
Tubular Rivet
A small rivet having a coaxial cylindrical hole in the headless end, designed for securing by splaying the end.
Tubular tire
A type of bicycle tire that has a tube sewn up inside the casing, also known as a sew-up.
A vehicle brand of which the 1948 models are milestone cars.
Reducing the length of certain sections of a panel. Opposite of Throwing. When making a panel with rounded edges that has to be folded along the inner edge, the radius along this edge must be increased and its length reduced; this is done by thickening the material in certain areas
A word coined by Ford for a 2-door sedan.
A boat equipped with powerful engines for towing or pushing large ships or barges
To clean, smooth, or polish in a rotating barrel or drum by friction with each other, assisted by added mediums, as scraps, balls, sawdust, sand, etc.
  1. The severe inward (concave) curvature used on the sides of some cars.
  2. The tilt of a panel of moveable glass such as the side windows as it aligns within the window frame.
  3. The inboard slope of a ship’s side above the designed waterline
  1. The smoothing of an aluminum surface by turning it over and over in rotating barrels with metallic or ceramic shot but without any form of abrasive
  2. To flip fasteners around like clothes in a dryer in order to clean fasteners and increase the shininess of stainless. Soap or a cleansing solution is often added.
To adjust the engine controls (carburetor, timing, etc.) for optimum running.

Tuned exhaust
Intake and exhaust systems that harness the pressure pulses and resonances inside the various passages and chambers of the intake and exhaust manifolds. In this way they increase the flow of intake charge into and out of the combustion chambers. Although the exhaust port must be a smooth as possible, the Intake port must not because the fuel must churn and mix with the air.
Tuned for economy
An engine (and often other components) which have been adjusted to use less fuel
Tuned header
Tuned port injection
(TPI) a GM fuel injection system that uses tuned air intake runners for improved airflow
That component/circuit of a radio which tunes to the frequencies of radio stations; (tuner + amplifier = receiver)
Tune up

  1. The intent of a tune-up is to obtain the maximum performance and economy of an engine with the lowest possible exhaust emissions so that the vehicle engine will meet the manufacturer’s Specifications. It involves checking the components of the ignition system and cleaning or replacing them; cleaning and adjusting the carburetion or fuel injection system; adjusting the points and timing cleaning and Gapping the spark plugs. Tune-ups should be performed according to the recommendation of each manufacturer.
  2. To disassemble the components of a bicycle, cleaning, adding lubricant, reassembling, replacing worn components (brake pads, chain, bearings, cables, tires), adjusting chain, brakes, derailleurs, and tire pressure in order to make the unit safe and efficient.
Tune up kit
Tune-up kit
A set of parts containing points, rotor, condenser, cam lube, and possibly a Feeler gauge. Each vehicle make, model, and year has its own tune-up kit.
Tungstate Screen
A hard, malleable, greyish-white element used in lamp filaments, electrical contact points and, alloyed with steel, in high-speed cutting tools
Tungsten-arc welding
Tungsten-halogen bulb
A quartz-halogen bulb with a tungsten filament
The adjustment of the carburetor, ignition timing, etc. to improve performance.

Tuning system
Tuning the exhaust
A passageway cut through a hill, cliff, or mountain

Tunnel drier
A heated tunnel through which body shells are passed in painting lines, e.g., to dry their phosphate coatings
Tunnel furnace
A heated tunnel through which body shells are passed in painting lines, e.g., to dry their phosphate coatings
Moving a component deeply into its surrounding sheet metal to give the appearance of being recessed, e.g., headlights, tall lights, and antennas
  1. A rotary machine which extracts mechanical shaft power from the working fluid (gas or liquid) using rotor vanes.
  2. A machine for generating rotary mechanical power from the energy of a stream of fluid (such as water, steam, or hot gas). Turbines convert the kinetic energy of fluids to mechanical energy through the principles of impulse and reaction, or a mixture of the two.
  3. A type of engine in which all the parts that are in regular motion are rotating, making for very smooth operation. The basic gas turbine operates as follows air enters the compressor and is compressed. It is then delivered to the combustion chamber under pressure and here the fuel is introduced, mixed with the air and burned, the quantity injected determining speed and power output. The hot, high-pressure burning gases then proceed to the first turbine, which drives the compressor and continue to the power turbine, which delivers power to the Output shaft through reduction gears. The gears are necessary because the speed of turbine rotation is measured in tens of thousands of rpm not thousands as with a typical piston engine. The turbine’s attractions include its utter simplicity and directness in getting power from burning gas, its smoothness, easy cold starting and its ability to run on almost any Hydrocarbon fuel. On the minus side are high cost, problems with materials because of the high temperatures and speed of rotation and relatively high NOx production.
Turbine casing
The casing enclosing a turbine
Turbine engine
An engine that uses burning gases to spin a turbine, or series of turbines, as a means of propelling the vehicle.


Turbine housing
The casing enclosing a turbine
Turbine wheel
  1. A turbocharger wheel driven by exhaust gases, the turbine wheel spins at speeds up to 160,000 rpm and drives the compressor which is located at the opposite end of the turbine shaft; wheel and shaft are usually inseparable.
  2. A driven member of a torque converter which transmits multiplied engine torque to the transmission input shaft
Abbreviation for turbocharger. In computers the term is erroneously used to mean an increase in speed.

Turbocharged engine
An engine fitted with a turbocharger
  1. An exhaust powered Turbine super-charger. Turbochargers always use centrifugal-flow compressors, which operate efficiently at the high rotational speeds produced by the exhaust turbine.
  2. A device used for increasing the pressure and density of a fluid entering a fuel cell power plant using a compressor driven by a turbine that extracts energy from the exhaust gas.

Turbo charger
  1. A method of increasing power and decreasing emissions by rerouting hot exhaust gases through a Turbine which drives a pump that forces more air into the engine cylinders.
  2. Using an exhaust-driven turbine to drive an air compressor that compresses air into the cylinders and increases the power of the engine.
  3. A process of compressing the engine intake air charge in order to allow more air and fuel into the cylinder and, thus, to increase the engine power output. The compressor, called the turbocharger, is driven by an exhaust gas propelled turbine.
Machine for compressing air or other fluid (reactant if supplied to a fuel cell system) in order to increase the reactant pressure and concentration.
A diesel engine which is turbocharged
Machine for expanding air or other fluid (reactant if supplied to a fuel cell system) in order to decrease the fluid pressure and concentration. The unit is normally used in conjunction with a compressor to recover unused energy from hot, pressurized gasses, thereby reducing the net amount of energy required to power the compressor.
Turbo gauge
A boost pressure gauge on turbocharged engines
Turbo Generator
Gas turbine combined with an electrical generator.
Turbo lag
  1. Within a turbocharger’s operating range, lag is the delay between the instant a car’s accelerator is depressed and the time the turbocharged engine develops a large fraction of the power available at that point in the engine’s power curve.
  2. The time delay between injecting fuel to accelerate and delivering air to the intake manifold by the turbocharger. This phenomenon may cause black smoke emissions in some turbocharged diesel engines during acceleration.
  1. Violent, broken movement or agitation of a fluid or gas.
  2. Rapid mixing and swirling of fuel, air, and gases within a combustion chamber. Improves engine performance and efficiency.

  1. To machine on a lathe
  2. To change direction
Turn a lap
To drive one full circle around the race track.
  1. A device which allows the linkage to be lengthened or shortened. A threaded hole is found on each end of the turnbuckle. The linkage which attaches to the turnbuckle can be screwed in or out on each end to create the necessary length. Usually a lock nut secures the turnbuckle in place. In some instances, the turnbuckle may have a threaded hole at one end and a threaded Stud at the other.
  2. A coupling, threaded right and left or swivelled on one end, for adjustably connecting two rods.
Turndown Factor
The moment of transition between driving straight ahead and cornering.
Turning circle
The smallest circle in which a vehicle can turn, i.e., with the wheels on full lock.

Turning over

Turning radius
  1. The diameter of the circle created by the outer front wheel when making a full turn. There are two ways of measuring the turning radius curb to curb and wall to wall. The latter is always larger because it takes into account front-end overhang. As the vehicle turns, the inside wheels make a smaller circle than the outside tires.
  2. The relation of one front wheel to the other on turns. If your tires are squealing on turns, have your front-end alignment checked to be sure that bent steering arms have not affected the turning radius of the car.
Turn-in rate
The way a car steers into a bend; the roll-steer effect
Turn into the skid
To turn the steering wheel in the same direction as that in which the rear of the car is sliding, in order to counteract the skid
A drainage ditch that drains water away from roads and road ditches.

Turn over
An engine is said to turn over when the starter has caused the crankshaft to begin to turn, which starts the pistons moving so that combustion can begin to take place in the cylinders providing power to move the vehicle.
A U.S. toll road, especially one that is an expressway
Turnpike Double
A combination vehicle consisting of a tractor and two 40 to 53 foot trailers.
Turn signal
Turn signal indicator
A light (usually accompanied by a click or chime) which flashes when the turn signal lever is engaged and the signal lights flash. Most are located somewhere on the instrument panel in front of the driver, but Cadillac and others also mounted them on the upper edge of the front and rear fender or the rear headliner.
A circular platform mounted under the front of a full trailer or a jeep dolly to which an axle or axles are attached, allowing the axles to pivot in a turning maneuver.
The inward sloping of a car’s body below the waistline
Turret Truck
Type of man-up lift truck with a rotating fork that can turn 90 degrees in either direction.
Turret web
Abbreviation for Throttle Valve
TVRClick image for books on

A brand of sports cars manufactured in Blackpool, England.

TV rod
This refers to the Throttle valve rod that extends from the foot throttle linkage to the throttle valve in the automatic transmission.
TVRS wire
A type of resistance wire used for spark plug wires. It minimizes ignition system interference with the radio and other electronic components on the vehicle
  1. Abbreviation for Thermal vacuum switch
  2. Abbreviation for Temperature vacuum switch
Abbreviation for Thermostatic vacuum switching valve
  1. Abbreviation for Thermal vacuum valve
  2. Thermal vent valve

Abbreviation for Three-way catalyst sometimes referred to as a dual catalytic converter. Combines two catalytic converters in one shell to control emissions of NOx, HC, and CO


  1. To adjust a screw or component by making a very slight adjustment.
  2. To bend a component to such an extent that it will need to be replaced.
Tween deck
The space between any two adjacent decks
Twelve-cylinder engine
An engine with twelve cylinders, e.g., a V-12
Twelve-valve engine
A three-cylinder engine with four valves per cylinder (e.g., Daihatsu), or a six-cylinder engine with two valves per cylinder, or a four-cylinder engine with three valves per cylinder, i.e., two inlet valves and one exhaust valve
Twenty Foot Equivalent Unit
(TEU) A standard for measuring container capacity on ships, railcars, etc.

Abbreviation for Tread wear indicators
Twilight sentinel
A device found on Cadillac cars which controls the headlights so that they remain on for a set period of time after the engine is shut off.
To construct a highway in which there are two lanes on each side of the road often with a center median dividing each pair of lanes. The British term is dual.

Twin A-arm suspension
Twin axle
Twin barrel carburetor
A carburetor with two identical barrels to feed two banks of cylinders
An engine with Double overhead camshafts.


Twin cam engine
An engine with Double overhead camshafts.
Twin camshaft
An engine with Double overhead camshafts.
Twin camshaft engine
An engine with Double overhead camshafts.
Twin carburetors
(TC) two carburetors on an engine, mechanically coupled and balanced
Twin-choke carburetor
A carburetor with two identical barrels to feed two banks of cylinders.

Twin diaphragm pump
A diaphragm pump with two diaphragms; if one fails the other takes over its function
Twin exhaust system
An exhaust system with two tailpipes; either a complete exhaust system, as on performance cars and cars with V-engines, or simply two tailpipes emanating from the rear muffler. Also called Dual exhaust system
Twin fitment
Twin front pipe

Twin header

Twin headlight
A headlight arrangement containing two headlights; the outer lights provide the low beams, the inner lights are for high beam
Twin headpipe

Twin Ignition
Twin ignition system
A distributor with two sets of contact points, each of which operates with its own coil in a separate primary circuit; the contact points open alternately, each set firing half of the cylinders
Twin I-beam suspension
Used on most Ford trucks in the last 20 years. This variation does not link the wheels, but uses two long beams, each pivoting on the opposite side of the vehicle. Results in a smoother ride, but creates tire-wear problems.
Twin overhead camshaft
Twin-piston engine
An obsolete two-stroke engine design featuring two cylinder barrels plus two pistons per cylinder; the pistons are linked to the crankshaft via a forked con rod or a master/slave con rod assembly
Twin planets
Two planet gears in mesh; one meshes with the sun gear and the other with the internal gear
Twin-plate clutch
A clutch with two driven plates separated by an intermediate drive plate; gives higher torque capacity
Twin plug ignition
Twin port
A cylinder head design in which there are two exhaust ports
  1. A motorcycle with two cylinders
  2. Combination of a tractor and two semitrailers connected in tandem by a Converter dolly. Also called Doubles or Twin Trailers
Twin Screw
A truck or tractor with two rear axles, both driven by the engine.
Twin-spar frame
A motorcycle frame in which the steering head and the swingarm pivot are connected by two metal (usually alloy) members (i.e., spars) that wrap around the sides of the engine
Twin spark ignition
Twin swirl combustion chamber
A special design of a four-stroke engine, in which the intake valves are arranged in such a way as to ensure that the gas flow ends in two separate swirls; this design improves swirl and thus enhances combustion of the fuel/air mixture within the cylinder
Twin Trailers
Combination of a tractor and two semitrailers connected in tandem by a Converter dolly. Also called Twins or Doubles
Twin-tube damper
Twin wheel
  1. A double-rimmed wheel with two independently inflated tires; has good aquaplaning and run-flat properties.
  2. Two wheels fitted to one hub
Twist-beam rear axle
Twist drill
A metal cutting drill with spiral Flutes (grooves) to permit the exit of chips while cutting.
Twisted frame
A type of frame damage often encountered as a result of the car rolling over. The left-hand and right-hand frame members are then no longer parallel and on a level when viewed from the side; instead, they are offset as if they had been turned on a horizontal axis at right angles to the frame members
Twist shifter
A type of shift lever that is twisted to shift the gears such as GripShift models
Twisty bits
The twisting back roads you can find in almost any state. The two lane roads that bring a sports car to life as you master the turns, curves and switchbacks.
Two bolt main
A term referring to the number of bolts needed to secure each cap to a crankshaft rod. Most engines come with two bolt main; but racing engines have four.

Two-coat system
Two-cycle engine
A vehicle with one door on each side; a body design typical of all two-seater sports cars (such as roadsters, spiders) and many subcompact cars
Two-door club coupe
Two-door coupe
Two-door coupeTwo-door coupe

Also called the two-door club coupe, the club coupe designation seems to come from club car, describing the lounge (or parlor car) in a railroad train. The early postwar club coupe combined a shorter-than-sedan body structure with the convenience of a full back seat, unlike the single-seat business coupe. That name has been used less frequently in the 1976-86 period, as most notchback two-door models (with trunk rather than hatch) have been referred to as just coupes. Moreover, the distinction between two-door coupes and two-door sedans has grown fuzzy.

Two-door fastback
Two-door fastbackTwo-door fastback

By definition, a fastback is any automobile with a long, moderately curving, downward slope to the rear of the roof. This body style relates to an interest in streamlining and aerodynamics and has gone in and out of fashion at various times. Some (Mustangs for one) have grown quite popular. Others have tended to turn customers off. Certain fastbacks are, technically, two-door sedans or pillared coupes. Four-door fastbacks have also been produced. Many of these (such as Buick’s late 1970s four-door Century sedan) lacked sales appeal. Fastbacks may or may not have a rear-opening hatch.

Two-door hatchback coupe
Two-door hatchback coupeTwo-door hatchback coupe

Originally a small opening in the deck of a sailing ship, the term hatch was later applied to airplane doors and to passenger cars with rear liftgates. Various models appeared in the early 1950s, but weather-tightness was a problem. The concept emerged again in the early 1970s, when fuel economy factors began to signal the trend toward compact cars. Technology had remedied the sealing difficulties. By the 1980s, most manufacturers produced one or more hatchback models, though the question of whether to call them two-door or three-door never was resolved. Their main common feature was the lack of a separate trunk. Liftback coupes may have had a different rear-end shape, but the two terms often described essentially the same vehicle.

Two-door hardtop
Two-door hardtopTwo-door hardtop

The term hardtop, as used for postwar cars up to the mid-1970s, describes an automobile styled to resemble a convertible, but with a rigid metal (or fiberglass) top. In a production sense, this body style evolved after World War II, first called hardtop convertible. Other generic names have included sports coupe, hardtop coupe, or pillarless coupe. In the face of proposed rollover standards, nearly all automakers turned away from the pillarless design to a pillared version by 1976-77.

Two-door sedan
Two-door sedanTwo-door sedan

The term sedan originally described a conveyance seen only in movies today a wheelless vehicle for one person, borne on poles by two men, one ahead and one behind. Automakers pirated the word and applied it to cars with a permanent top, seating four to seven (including driver) in a single compartment. The two-door sedan of recent times has sometimes been called a pillared coupe, or plain coupe, depending on the manufacturer’s whim. On the other hand, some cars commonly referred to as coupes carry the sedan designation on factory documents.

Two-door station wagon
Two-door station wagonTwo-door station wagon

Originally defined as a car with an enclosed wooden body of paneled design (with several rows of folding or removable seats behind the driver), the station wagon became a different and much more popular type of vehicle in the postwar years. A recent dictionary states that such models have a larger interior than sedans of the line and seats that can be readily lifted out, or folded down, to facilitate light trucking. In addition, there’s usually a tailgate, but no separate luggage compartment. The two-door wagon often has sliding or flip-out rear side windows.

Two-pack filler
All polyester fillers in use today comprise a basic filler paste and a hardener or catalyst
Two-pack paint
Paint prepared by mixing two constituents, such as pigment and an acrylic resin
An AC system using two phases whose voltages are displaced from each other by 90 electrical degrees. Also called bi-phase
Two-piece alloy wheel
A wheel which consists of the rim and the wheel disc or spider bolted together. The word forged is optional, since multi-piece alloy wheels are always forged and not cast
Two-piece forged alloy wheel
A wheel which consists of the rim and the wheel disc or spider bolted together. The word forged is optional, since multi-piece alloy wheels are always forged and not cast
Two plus two
(2+2) A two-door car with seating for the driver and a front passenger and only two people in the rear. It differs from a regular two-seater in that generally three people could sit in the rear seat and possibly three in the front. Usually the rear seats are very small and suitable only for children, small pets, or extra luggage.
Two-pole motor
3600 rpm, 60 Hz electric motor (synchronous speed).
Two second rule
The minimum gap or distance between two vehicles traveling in the same direction. As the vehicle in front of you passes a particular mark on the road or sign along the road, count two seconds and your vehicle should pass the same mark or sign. If road conditions are poor, the gap should be extended to three seconds or more. If you are following less than two seconds, there is not sufficient time to react to emergency evasive maneuvers to avoid the possibility of hitting the vehicle in front.
An electric motor or transmission having two speed settings (e.g., fan, windshield wiper)
Two-speed axle
Axle having two selective gear ratios.
Two-speed gearbox
Two-speed transmission
An automatic transmission with just two speeds (Drive and Low) such as the GM Powerglide popular in the 1960s
Two-stage carburetor
A compound carburetor
Two-stage pump
A centrifugal pump with two impellers and diffusers arranged in series
Two-staged turbo
Since there is often a lag while a turbine comes up to speed, some performance cars use two (or more) turbo units, large and small, driven by different legs of the exhaust. The smaller turbos speed up quickly giving rapid response, and the larger units provide the volume needed for high power at higher rpm’s.

Two stroke cycle
Two stroke cycle engine
Two-stroke cycle
The operating principle of an internal combustion engine characterized by the fact that the intake, compression, combustion, and exhaust phases overlap and require only two cycles; used mainly by some motorcycle engines. On cars, the two-stroke engine was never very popular and was never produced in the USA (although Ford is experimenting with the engine); a new two-stroke engine concept with separate lubrication system and a valve system similar to four-stroke engines may combine the benefits of both the 2-stroke and the 4-stroke systems. Two-stroke engines have the advantage of rapid low-end torque (because it gets its power stroke twice as often) while 4-strokes are better at sustained high-speed.
Two-stroke cycle engine
An engine requiring one complete revolution of the crankshaft to fire each piston once.

Two stroke
A Reciprocating engine cycle in which the piston takes over some of the valve functions in order to obtain a Power stroke each revolution of the crankshaft. This involves the use of Ports in the cylinders which are covered and uncovered by the movements of the piston. As the piston moves down, it clears these ports so that the exhaust gases can exit and a fresh charge of mixture can enter at the same time. In a typical two-stroke engine the fuel-air mixture enters the crankcase through a Reed valve. When the piston is at the bottom of the cylinder a port is uncovered. As prior movement of the piston has compressed the mixture in the crankcase it flows into the cylinder. Further compression in the cylinder starts as soon as the piston reverses and covers the ports. At the same time compression is occurring in the cylinder, movement of the piston has created a vacuum in the crankcase which draws a fresh charge of mixture from the carburetor into the crankcase. The compressed charge is fired as the piston reaches Top dead center. As Expansion of the burning charge forces the piston downward, the reed valve in the crankcase closes and the mixture in the crankcase is compressed. As the piston uncovers the ports at the bottom of the stroke, compressed mixture from the crankcase enters the cylinder again and is deflected by a Baffle on the Piston head into the outer end of the cylinder. This incoming fresh mixture then assists in pushing the burned gases out of the cylinder and the cycle is repeated.
Two-temperature valve
Pressure-opened valve used in suction line on multiple refrigerator installations which maintains evaporators in system at different temperatures.
Two-tone horn
Two horns whose diaphragms cause a column of air to resonate at two different frequencies
Two-tone paint
A paint scheme where two different colors or two shades of the same color are used on a vehicle.
Two up
A term for carrying a passenger on your motorcycle.

Two-valve engine
An engine with two valves per cylinder
Two-valve head
A cylinder head with two valves per cylinder
Two-way catalyst
Two-way catalytic converter
Two-way hammer
A hammer used for dual purposes
Two-way radio
Two-way system
A turbocharging system in which, as long as the charging pressure is insufficient, the air is drawn in from a prechamber via a diaphragm valve; with rising charging pressure, the valve closes and the turbocharger delivers air via the surge tank connected to a pressure regulator
Two-way type check valve
A unit which permits actuation of a brake system by either of the two brake application valves

Two-way valve
Valve with one inlet port and one outlet port.
Two-wheel ABS
An anti-lock brake system that operates on only the rear wheels.
Two-wheel drive
(2WD) A vehicle’s drive system in which two of the four wheels (either front or rear) are driven. Compare Four-wheel drive
Two-wheel driven
A vehicle with two-wheel drive; also written 4×2
Two wheeler
Trucker slang for Motorcycle as in ‘We got a two wheeler coming up fast in the left lane.’
TW sensor
Short for Coolant temperature sensor
Abbreviation for Three Way Solenoid Valve
Type A motorhome
A large, most luxurious motorized recreational vehicle. It is constructed on a bare, specially designed motor vehicle chassis. It is the most spacious and includes most luxuries basement storage, washer & dryer, satellite dishes, VCRs, back-up cameras, hydraulic leveling, security systems, and even hot tubs. Also called Class A RV
Type approval certificate
A British certificate issued by the Department of Transport denoting that a particular vehicle type meets official requirements
Type A School Bus
A van conversion or bus constructed using a small cowl and chassis, van-based cutaway. Has a nose and grille like a typical van, a regular driver’s door (on the left side of vehicle), and the passenger entrance door curbside, behind the front wheel. Front engine location.
Type axle
Type B motorhome
Also called a van camper, it is a customized cargo van which includes temporary sleeping, eating, and bathroom facilities. It is the most economical, versatile, and maneuverable of the motorized recreational vehicles. It is narrower than other RVs because it uses the space within the existing van body. However, most are equipped with a raised roof and sometimes a dropped floor to provide full stand-up room. Also called Class B RV
Type B School Bus
A school bus constructed on a stripped van or truck chassis, perhaps resembling a step-van type of front. Full coach body, with only one door, curbside, behind the front wheels. Front engine location.
Type C motorhome
Also called a mini-motorhome, is built on the frame and front cab section of a manufacturer’s van. A sleeping bunk is mounted above the cab as well as one in the back. It features full sleeping, kitchen, dining, and bathroom facilities. Also called Class C RV
Type C School Bus
A conventional school bus consisting of a coach body mounted on a truck-based, flat back cowl (big cowl and chassis: Hood and fender assembly). Varying lengths and some have wheelchair lifts. There is typically one entrance door located behind the front wheels. Front engine location.
Type designation
A spark plug designation indicating seat and thread type, version, heat range code number, reach, spark position, and electrode material
Type D School Bus
A transit-style school bus. Flat front, full coach body mounted on stripped bus chassis. Can be either front (forward control) or rear engine. Varying lengths, can have wheelchair lift and small storage compartments under passenger floor (accessed though small hatch doors on side of bus).
Type symbol
A spark plug designation indicating seat and thread type, version, heat range code number, reach, spark position, and electrode material
A British term for Tire. The British smile when they see a sign saying Goodyear tires which implies lethargy in Goodyear.
A trade name for a form of rayon produced exclusively for tire cords.