Automotive Glossary of Terms - T -
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Definitions for automotive terms and illustrations from tachometer to turn over engine.
TACHOMETER: A device used to measure the rotary speed of an engine, shaft, gear, etc., usually in rotations per minute.
TAMPERING: Used in conjunction with a vehicles emission control system. Tampering is used to describe any alterations to the original design of the vehicles emission control system.
TAMPERING INSPECTION: An inspection done by State or Local authorities to determine if a vehicle's emission control system has been tampered with.
TDC: Top dead center. The exact top of the piston's stroke.
THERMOSTAT: A valve, located in the cooling system of an engine, which is closed when cold and opens gradually in response to engine heating, controlling the temperature of the coolant and rate of coolant flow.
THROW-OUT BEARING: As the clutch pedal is depressed, the throwout bearing moves against the spring fingers of the pressure plate, forcing the pressure plate to disengage from the driven disc.
TIE ROD: A rod connecting the steering arms. Tie rods have threaded ends that are used to adjust toe-in.
TIMING BELT: A square-toothed, reinforced rubber belt that is driven by the crankshaft and operates the camshaft.
TIMING CHAIN: A roller chain that is driven by the crankshaft and operates the camshaft.
TIRE ROTATION: Moving the tires from one position to another to make the tires wear evenly.
TOE-IN (OUT): A term comparing the extreme front and rear of the front tires. Closer together at the front is toe-in; farther apart at the front is toe-out.
TOP DEAD CENTER (TDC): The point at which the piston reaches the top of its travel on the compression stroke.
TORQUE: Measurement of turning or twisting force, expressed as foot-pounds or inch-pounds.
TORQUE CONVERTER: A turbine used to transmit power from a driving member to a driven member via hydraulic action, providing changes in drive ratio and torque. In automotive use, it links the driveplate at the rear of the engine to the automatic transmission.
TORSION BAR SUSPENSION: Long rods of spring steel which take the place of springs. One end of the bar is anchored and the other arm (attached to the suspension) is free to twist. The bars' resistance to twisting causes springing action.
TRACK TIRES: Distance between the centers of the tires where they contact the ground.
TRACTION CONTROL: A control system that prevents the spinning of a car's drive wheels when excess power is applied.
TRANSAXLE: A single housing containing the transmission and differential. Transaxles are usually found on front engine/front wheel drive or rear engine/rear wheel drive cars.
TRANSDUCER: A device used to change a force into an electrical signal.
TRANSFER CASE GEARBOX: A gearbox driven from the transmission that delivers power to both front and rear driveshafts in a four-wheel drive system. Transfer cases usually have a high and low range set of gears, used depending on how much pulling power is needed.
TRANSISTOR: A semi-conductor component which can be actuated by a small voltage to perform an electrical switching function.
TREAD WEAR INDICATOR: Bars molded into the tire at right angles to the tread that appear as horizontal bars when 1/ 16 th in. of tread remains.
TREAD WEAR PATTERN: The pattern of wear on tires which can be "read" to diagnose problems in the front suspension.
TSB: Acronym for Technical Service Bulletin. This bulletin is produced by the vehicle manufacturer and alerts automotive technicians about specific service problem areas, repair procedures, and new service techniques for a vehicle.
TUNE-UP: A regular maintenance function, usually associated with the replacement and adjustment of parts and components in the electrical and fuel systems of a car for the purpose of attaining optimum performance.
TURBOCHARGER: An exhaust driven pump which compresses intake air and forces it into the combustion chambers at higher than atmospheric pressures. The increased air pressure allows more fuel to be burned and results in increased horsepower being produced.
TURN OVER ENGINE: Synonymous with "cranks over", the action of the engine internal components rotating during the starting cycle. This is what happens when you turn the key before the engine starts.