Dictionary of Automotive Terms: T

TACHOMETER: Device used to indicate speed of engine in rpm.

TAILLIGHT: Lights, usually red or amber, attached to rear of vehicle. Lights operate in conjunction with headlights.

TAIL PIPE: Exhaust piping running from muffler to rear of car.

TANK GAUGE UNIT: Variable resistor device in fuel tank. It operates fuel gauge in dashboard.

TAP: To cut threads in a hole, or can be used to indicate fluted tool used to cut threads.

TAP AND DIE SET: Set of taps and dies for internal and external threading—usually covers a range of the most popular sizes.

TAPERED ROLLER BEARING (Antifriction): Bearing utilizing series of tapered, hardened steel rollers operating between an outer and inner hardened steel race.

TAPPET: Screw used to adjust clearance between valve stem and lifter or rocker arm.

TAPPET NOISE: Noise caused by lash or clearance between valve stem and rocker arm or between valve stem and valve lifter.

TCS: Transmission Controlled Spark.

TDC: Top Dead Center.

TEFLON: Plastic with excellent self- lubricating (slippery) bearing properties.

TEMPER: To effect a change in physical structure of piece of steel through use of heat and cold.

TEMPERATURE GAUGE: Dash mounted instrument to indicate temperature of engine coolant. May be operated electrically or by Bourdon tube.

TENSION: Pulling or stretching stress applied to an object.

TERMINAL: Connecting point in electric circuit. When referring to battery, it would indicate two battery posts.

T-HEAD ENGINE: Engine having intake valve on one side of cylinder and exhaust on other.

THERMAL EFFICIENCY: Percentage of heat developed in burning fuel charge that's actually used to develop power determines thermal efficiency. Efficiency will vary ac cording to engine design, use, etc. If an engine utilizes great deal of heat to produce power, its thermal efficiency would be high.

THERMISTOR: Resistor that changes its resistance in relation to temperature fluctuations.

THERMOSTAT: Temperature sensitive de vice used in cooling system to control flow of coolant in relation to temperature.

THERMOSTATICALLY CONTROLLED AIR CLEANER (TAC): An emission control device used to control temperature of air entering air cleaner. Cleaner receives heated air during engine warmup.

THERMOSTATIC SWITCH: A switch that's actuated by temperature changes.

THIRD BRUSH (Generator): Generator in which a third, movable brush is used to control current output.

THREE-QUARTER RACE CAMSHAFT: Description of custom camshaft indicating type of lobe grinding which, in turn, dictates type of use. Other grinds are one-quarter race, full-race, street-grind, etc.

THREE-WAY CATALYTIC CONVERTER: Converter, sometimes called dual converter, that combines both an oxidizing and reducing catalyst. Controls NOx, CO, and HC emissions.

THROTTLE RETURN DASHPOT: Carburetor device which slows throttle closing and prevents stalling.

THROTTLE VALVE: Valve in carburetor. It is used to control amount of fuel mixture that reaches cylinders.

THROTTLE VALVE SENSOR AND THROTTLE POSITION SENSOR: Sensor which measures amount of throttle valve opening and provides information for fuel injection computer.

THROTTLE VALVE (Transmission): Valve in automatic transmission which controls oil flow to regulator plug.

THROW: Offset portion of crankshaft designed to accept connecting rod.

THROWING A ROD: When an engine has thrown a connecting rod from crankshaft, major damage is usually incurred.

THRUST: A pushing or shoving force exerted against one body by another.

THRUST BEARING: Bearing designed so as to resist side pressure.

THRUST SURFACE: That portion (surface) of a part that either receives or transmits a force from or to another part.

THRUST WASHER: Bronze or hardened steel washer placed between two moving parts. The washer prevents longitudinal movement and provides a bearing surface for thrust surfaces of parts.

TIE ROD: Rod, or rods, connecting steering arms together. When tie rod is moved, wheels pivot.

TIG: Gas tungsten arc welding (Tungsten Inert Gas).

TIMED FUEL INJECTION: Fuel injection is timed to occur when intake valve opens.

TIMING: The act of coordinating two or more separate events or actions in relation to each other. Example: Timing the firing of plug to piston position on compression stroke.

TIMING BELT: A flexible, toothed belt used to rotate camshaft.

TIMING CHAIN: Drive chain that operates camshaft by engaging sprockets on camshaft and crankshaft.

TIMING COVER: Cover over front of engine. Houses timing chain or gear mechanism and front crankshaft oil seal.

TIMING GEARS: Both the gear attached to the camshaft and the gear on the crankshaft. They provide a means of driving the cam shaft.

TIMING LIGHT: Stroboscopic unit that's connected to secondary circuit to produce flashes of light in unison with firing of specific spark plug. By directing these flashes of light on whirling timing marks, marks appear to stand still. By adjusting distributor, timing marks may be properly aligned, thus setting timing.

TIMING MARKS (Ignition): Marks, usually located on vibration damper, used to synchronize ignition system so plugs will fire at precise time.

TIMING MARKS (Valves): 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 other gear between two of teeth. Two gears must be meshed so that marked tooth meshes with marked spot on other gear.

TIMING SPROCKETS: Chain type sprockets on crankshaft and camshaft.

TINNING: Coating piece of metal with a very thin layer of solder.

TIRE BALANCE: In that tires turn at relatively high speeds, they must be carefully balanced both for static balance and for dynamic balance.

TIRE BEAD: Portion of tire that bears against rim flange. Bead has a number of turns of steel wire in it to provide great strength.

TIRE CASING: Main body of tire exclusive of tread.

TIRE INFLATION PRESSURE: Recommended maximum tire air pressure as given on tire sidewall.

TIRE PLIES: Layers of nylon, rayon, etc., cloth used to form casing. Many car tires are two ply with a four ply rating. Two ply indicates two layers of cloth or plies.

TIRE ROTATION: Moving front tires to rear and rear to front to equalize any wear irregularities.

TIRE SIDEWALL: Portion of tire between tread and bead.

TIRE SIZE: Given on tire sidewall as coded letter-number designation of size, section height, and diameter across bead.

TIRE TREAD: Part of tire that contacts road.

TOE-IN: Having front of wheels closer together than the back (front wheels). Difference in measurement across front of wheels and the back will give amount of toe-in.

TOE-OUT: Having front of wheels further apart than the back.

TOE-OUT ON TURNS: When car negotiates a curve, inner wheel turns more sharply and while wheels remain in this position, a condition of toe-out exists.

TOGGLE SWITCH: Switch actuated by flip ping a small lever either up and down or from side to side.

TOLERANCE: Amount of variation permitted from an exact size or measurement. Actual amount from smallest acceptable dimension to largest acceptable dimension.

TOOTH HEEL (Differential Ring Gear): Wider outside end of tooth.

TOOTH TOE (Differential Ring Gear): Narrower inside end of tooth.

TOP OFF: Fill a container to full capacity.

TORQUE: Turning or twisting force such as force imparted on drive line by engine.

TORQUE BAR or ROD: An articulated bar between frame and drive axle housing de signed to relieve leaf springs of axle torque (twisting) strain. Prevents axle windup and/or hop during heavy acceleration or braking. Also called Traction Bar.

TORQUE CONVERTER: Unit, quite similar to fluid coupling, that transfers engine torque to transmission input shaft. Unlike fluid coupling, torque converter can multi ply engine torque. This is accomplished by installing one or more stators between torus members. In torque converter, driving torus is referred to as “pump” and driven torus as “turbine.”

TORQUE (Gross): Maximum engine torque developed by engine without fan, air cleaner, alternator, exhaust system, etc.

TORQUE (Net): Maximum torque developed by engine equipped with fan, air cleaner, exhaust system, and all other systems or units normally present when engine is installed in the vehicle.

TORQUE MULTIPLICATION (Automatic Transmission): Increasing engine torque through the use of a torque converter.

TORQUE TUBE DRIVE: Method of connecting transmission output shaft to differential pinion shaft by using an enclosed drive shaft. Drive shaft is enclosed in torque tube that's bolted to rear axle housing on one end and is pivoted through a ball joint to rear of transmission on other. Driving force of rear wheels is transferred to frame through torque tube.

TORQUE WRENCH: Wrench used to draw nuts, cap screws, etc., up to specified tension by measuring torque (turning force) being applied.

TORSIONAL VIBRATION: Twisting and untwisting action developed in shaft. It is caused either by intermittent applications of power or load.

TORSION BAR: Long spring steel rod attached in such a way that one end is anchored while other is free to twist. If an arm is attached at right angles to free end, any movement of arm will cause rod or bar to twist. Bar’s resistance to twisting provides a spring action. Torsion bar replaces both coil and leaf springs in some suspension systems.

TORSION BAR SUSPENSION: Suspension system that makes use of torsion bars in place of leaf or coil spring.

TORUS: Fluid coupling rotating member. There are two — driving and driven torus.

TPC: Tire Performance Criteria.

TRACK: Distance between front wheels or distance between rear wheels. They are not always the same.

TRACTION BAR: Articulated bar or link attached to both frame and rear axle housing to prevent spring windup (with resultant wheel hop) during heavy acceleration or braking.

TRACTION DIFFERENTIAL: See Limited- Slip Differential.

TRACTION (Tire): Frictional force generated between tire and road. Necessary for braking, steering, and driving.

TRAMP: Hopping motion of front wheels.

TRANSAXLE: Drive setup in which trans mission and differential are combined into a single unit.

TRANSDUCER: Vacuum regulator actuated or controlled electrically. A device that converts an input signal (electrical) into an out put signal (diaphragm movement) of a different form.

TRANSFER CASE: Gearbox, driven by transmission, that will provide driving force to both front and rear propeller shafts on four-wheel drive vehicle.

TRANSFORMER: Electrical device used to increase or decrease voltage. Car ignition coil transforms voltage from 12 volts to up ward of 30,000 volts.

TRANSISTOR: Electrical device made of semi-conducting material and using at least three electrical connections. Often used as a switching device.

TRANSISTOR IGNITION: Form of ignition system utilizing transistors and a special coil. Conventional distributor and point setup is used. With transistor unit, voltage remains constant, thus permitting high engine rpm without resultant engine “miss.” Point life is greatly extended as transistor system passes a very small amount of cur rent through points.

TRANSMISSION: Device that uses gearing or torque conversion to effect a change in 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. Reduction in engine rpm in relation to wheel rpm produces a higher road speed but delivers less torque to driving wheels.

TRANSMISSION ADAPTER: A unit that allows a different make or year transmission to be bolted up to original engine.

TRANSMISSION (Automatic): Transmission that automatically effects gear changes to meet varying road and load conditions. Gear changing is done through series of oil operated clutches and bands.

TRANSMISSION BRAKE: A brake of either drum or disc design, working at transmission. Stops rotation of propeller shaft.

TRANSMISSION (Standard or Conventional): Transmission that must be shifted manually to effect a change in gearing.

TRANSVERSE LEAF SPRING: Leaf spring mounted so it's at right angles to length of car.

TRAPS: Area over which car is raced for timing purposes.

TREAD: Distance between two front or two rear wheels.

TREAD (Tire): Portion of tire which contacts roadway.

TREAD WIDTH (Tire): Distance between outside edges of tread as measured across tread surface.

TRIP ODOMETER: Auxiliary odometer that may be reset to zero at option of driver. Used for keeping track of mileage on trips up to one thousand miles.

TROUBLESHOOTING: Diagnosing engine, transmission, etc., problems by various tests and observations.

TRS: Transmission Regulated Spark.

TRUNNION: One of two pivots, bearings, etc., placed opposite to each other so as to permit a swiveling or tilting action of some part. Example: Universal joint trunnion (yoke bearings) that allow cross to swivel.

TUBE CUTTER: Tool used to cut tubing by passing a sharp wheel around and around tube.

TUBELESS (Tire): Tire constructed for use without inner tube, valve stem snaps into and seals in wheel rim.

TUNE-UP: Process of checking, repairing, and adjusting carburetor, spark plugs, points, belts, timing, etc., in order to obtain maximum performance from engine.

TURBINE: Wheel upon which series of angled vanes are affixed so moving column of air or liquid will impart a turning motion to wheel.

TURBINE ENGINE: Engine that utilizes burning gases to spin a turbine, or series of turbines, as a means of propelling the car.

TURBOCHARGER: Exhaust powered supercharger.

TURBULENCE: Violent, broken movement or agitation of a fluid or gas.

TURNING RADIUS: Diameter of circle transcribed by outer front wheel when making a full turn.

TV ROD: Throttle valve rod that extends from foot throttle linkage to throttle valve in automatic transmission.

TVS: Thermostatic Vacuum Switch.

TWIST DRILL: Metal cutting drill with spiral flutes (grooves) to permit exit of chips while cutting.

TWO-STROKE CYCLE ENGINE: Engine requiring one complete revolution of crankshaft to fire each piston once.