Automotive terms Modern (T)
Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.
The following are examples of Mid Modern technical terms recommended for general use worldwide. For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.
TACHOMETER:
A device used to measure the rotary speed of an engine, shaft, gear, etc., usually in rotations per minute.
TDC:
Top dead center. The exact top of the piston's stroke.
TEFLON SEALING RINGS:
Teflon is a soft, durable, plastic-like material that is resistant to heat and provides excellent sealing. These rings are
designed with either scarf-cut joints or as one-piece rings. Teflon sealing rings have replaced many metal ring applications.
TERMINAL:
A device attached to the end of a wire or cable to make an electrical connection.
TEST LIGHT, CIRCUIT-POWERED:
Uses available circuit voltage to test circuit continuity
TEST LIGHT, SELF-POWERED:
Uses its own battery source to test circuit continuity.
THERMISTOR:
A special resistor used to measure fluid temperature; it decreases its resistance with increases in temperature.
THERMOSTAT:
A valve, located in the cooling system of an engine, which is closed when cold and opens gradually in response to engine heat-
ing, controlling the temperature of the coolant and rate of coolant flow.
THERMOSTATIC ELEMENT:
A heat-sensitive, spring-type device that controls a drain port from the upper sump area to the lower sump. When the transaxle fluid reaches operating temperature, the port is closed and the upper sump fills, thus reducing the fluid level in the lower sump,
THROTTLE POSITION (TP) SENSOR:
Reads the degree of throttle opening; its signal is used to analyze engine load conditions. The ECM/PCM decides to apply the TCC, or to disengage it for coast or load conditions that need a converter torque boost.
THROTTLE PRESSURE/MODULATOR PRESSURE:
A hydraulic signal oil pressure relating to the amount of engine load, based on either the amount of throttle plate opening or engine vacuum.
THROTTLE VALVE:
A regulating or balanced valve that is controlled mechanically by throttle linkage or engine vacuum, It sends a hydraulic sig- to the shift valve body to control shift timing and shift quality, (See balanced modulator valve)
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.
TIE-UP:
Condition where two opposing clutches are attempting to apply at same time, causing engine to labor with noticeable loss of engine rpm.
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 (TOC):
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.
TORQUE CONVERTER CLUTCH:
The apply plate (lockup plate) assembly used for mechanical power flow through the converter.
TORQUE PHASE:
Sometimes referred to as slip phase or stall phase, torque multiplication occurs when the turbine is turning at a slower speed than the impeller, and the stator is reactionary (stationary). This sequence generates a boost in output torque.
TORQUE RATING (STALL TORQUE):
The maximum torque multiplication that occurs during stall conditions, with the engine at wide open throttle (WOT) and zero turbine speed.
TORQUE RATIO:
An expression of the gear ratio factor on torque effect. A 3:1 gear ratio or 3:1 torque ratio increases the torque input by the ratio factor of 3. Input torque (100 ft. lbs.) x 3 = output torque (300 ft. lbs.)
TRACTION:
The amount of usable tractive effort before the drive wheels slip on the road contact surface.
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:
Distance between the centers of the tires where they contact the ground.
TRACTION CONTROL:
A control system that prevents the spinning of a vehicle's drive wheels when excess power is applied
TRACTIVE EFFORT:
The amount of force available to the drive wheels,to move the vehicle.
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 that changes energy from one form to another. For example, a transducer in a microphone changes sound energy to electrical energy. In automotive air-conditioning controls used in auto-matic temperature systems, a transducer changes an electrical signal to a vacuum signal, which operates mechanical doors.
TRANSMISSION:
A powertrain component designed to modify torque and speed developed by the engine; also provides direct drive, reverse, and neutral.
TRANSMISSION CONTROL MODULE (TCM):
Manages transmission functions, These vary according to the manufacturer's product design but may include converter clutch operation, electronic shift scheduling, and mainline pressures
TRANSMISSION FLUID TEMPERATURE (TFT) SENSOR:
Originally called a transmission oil temperature (TOT) sensor, this input device to the ECM/PCM senses the fluid temperature and provides a resistance value. It operates on the thermislor principle,
TRANSMISSION INPUT SPEED (TIS) SENSOR:
Measures turbine shaft (input shaft) rpm's and compares to engine rpm's to determine torque converter slip. When compared to the transmission output speed sensor or VSS, gear ratio and clutch engagement timing can be determined.
TRANSMISSION OIL TEMPERATURE (TOT) SENSOR:
(See trans- mission fluid temperature (TFT) sensor.)
TRANSMISSION RANGE SELECTOR (TRS) SWITCH:
Tells the module which gear shift position the driver has chosen.
TRANSFER CASE:
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 in. of tread remains.
TREAD WEAR PATTERN:
The pattern of wear on tires which can be "read" to diagnose problems in the front suspension.
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 vehicle for the purpose of attaining optimum performance.
TURBINE:
The output (driven) member of a fluid coupling or fluid torque converter. It is splined to the input (turbine) shaft of the transmission.
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.
TURBULENCE:
The interference of molecules of a fluid (or vapor) with each other in a fluid flow.
TYPE F:
Transmission fluid developed and used by Ford Motor Company up to 1982. This fluid type provides a high coefficient of friction. TYPE 7176: The preferred choice of transmission fluid for Chrysler automatic transmissions and transaxles. Developed in 1986, it closely resembles Dexron and Mercon. Type 7176 is the recommended service fill fluid for all Chrysler products utilizing a lockup torque converter dating back to 1978.
