THROW-OUT BEARING- Bearing that decreases friction between the clutch fork and pressure plate.

TIE ROD- Connectors between rack ends and steering knuckles.

TIMING ADVANCE- Making the spark plug fire sooner in the compression stroke.

TIRE- The casing-and-tread assembly that is mounted on a vehicle to provide pneumatically cushioned contact and traction with the road.

TIRE BEAD- Wire ring encased in rubber that helps hold the tire sidewall against the rim.

TIRE IMPACT DAMAGE- Punctures, cuts, or tears caused by running over debris in the road.

TIRE MARKINGS- Information shown on the sidewall to indicate inflation pressure, load-carrying ability, size, and other data.

TIRE PLY- Layer of fabric or other material that forms the carcass or body of the tire.

TIRE ROTATION- Moving tires to different wheels periodically to even out wear.

TIRE WEAR ANGLE- Usually, a reference to camber because tilting the wheels puts more load on one side of the tire tread than on the other side.

TIRE WEAR PATTERN- Areas of tread that are worn off, which can provide information on causes of wear.

TOE- Degree to which opposing wheels are on converging or diverging lines (not parallel). Also, the narrow part of a gear tooth.

TOE-OUT ON TURNS- Steering feature that turns the inside wheel more sharply than the outside wheel.

TORQUE CONVERTER- Fluid coupling that acts as a clutch on an automatic transmission.

TORQUE MULTIPLICATION- Variation in torque achieved by turning the impeller of a torque converter faster than the turbine.

TORQUE TUBE- A solid steel drive shaft enclosed in a hollow tube with a single swivel joint at the front.

TORSION BAR- Spring steel rod that operates by twisting and untwisting.

TORSION SPRINGS- Small coil springs that help absorb the shock and vibration that occur when the clutch engages.

TRACKING- The position or direction of the front wheels in relation to the rear wheels.

TRACK ROD- Metal rod used to prevent axle side-to- side movement when cornering.

TRAM GAUGE- Instrument used to compare distances between the front and rear set of tires for toe adjustment.

TRANSAXLE- A combination of transmission and differential in one case, used on front-wheel drive vehicles.

TRANSAXLE DIFFERENTIAL- Transaxle assembly that transfers torque to the driving wheels and allows them to rotate at different speeds.

TRANSAXLE GEARBOX- The transmission section of the transaxle, housing the forward and reverse gears.

TRANSAXLE INPUT SHAFT- Main shaft that turns the gears in a transaxle.

TRANSAXLE OUPUT SHAFT- Shaft that transfers power to the ring and pinion gears of the differential.

TRANSFER CASE- A power takeoff unit that sends power to both the front and rear axle assemblies on a multiwheel drive vehicle.

TRANSISTOR- Tiny electronic component that functions as a switch, but has no moving parts.

TRANSMISSION CASE- Metal housing surrounding and supporting the transmission.

TRANSMISSION COOLER- A small separate radiator, used to cool transmission oil in vehicles pulling heavy loads.

TRANSMISSION LINKAGE- System that connects the shift lever with the transmission shift forks.

TRANSMISSION OIL COOLER- Small tank within the radiator, used to regulate transmission fluid temperature.

TRIGGER WHEEL- Rotating component with one tooth for each cylinder.

TRIPOD CV-JOINT- Constant velocity joint used on front-wheel drive vehicles, consisting of a spider and ball arrangement inside a housing.

TUBELESS- A tire that does not have a separate inner tube to hold air.

TURBINE- The driven fan in a torque converter.
TURNING- Tem, usually used for machining a brake drum or rotor, since this process is carried out on a lathe.

TURNING RADIUS GAUGE- Instruments that measure how many degrees left or right the front wheels are turned.

U-JOINT ALIGNMENT MARKS- Scribed marks made on U-joint components before disassembly, allowing the joint components to be reassembled in the same positions to avoid possible imbalance and vibration.

UNDER INFLATION- Operating tires with a lower than recommended air pressure.

UNIBODY- A vehicle structure in which the body and frame are one unit.

UNIVERSAL JOINT- A flex joint allowing limited up-and-down and side-to-side movement.

UNSPRUNG WEIGHT- The weight of the vehicle parts that are not supported by the springs, such as the wheels.

VACUUM ADVANCE- A mechanism on the ignition distributor that uses intake manifold vacuum to advance the timing of the spark to the spark plugs.

VACUUM MODULATOR- A device that modulates, or changes, the main-line hydraulic pressure in an automatic transmission to meet changing engine loads.

VALVE BODY- Housing that contains most of the valves used in operation of an automatic transmission.

VALVE CORE- A threaded air valve that screws into place in a valve stem.

VALVE STEM- A rubber inflation tube with a threaded metal core that snaps into a hole on the rim of a wheel designed for tubeless tires.

VALVE STEM CAP- A cap placed over the end of the valve stem to prevent stem wear.

VOLTAGE- Electrical pressure that causes current flow.

VOLTAGE DROP- Reduction of the amount of current flowing in a circuit.

VOLTGAE DROP TEST- Starting system test that identifies parts showing high resistance.

VOLTAGE REGULATOR- Device used to control alternator output.

WEAR BAR- Solid bars of rubber across the tread that appears when a tire has worn to an unsafe limit.

WET CHARGED- Battery that is filled with electrolyte and fully charged at the factory.

WHEEL ALIGNMENT- Adjusting wheels of a vehicle to roll in a straight line.

WHEEL BEARING- Ball or roller bearing assemblies that reduce friction as wheels or axles rotate.

WHEEL BRAKE ASSEMBLIES- Components that use hydraulic pressure to apply friction for stopping a vehicle.

WHEEL CYLINDER- Hydraulic piston that actuates braking at each wheel.

WHEEL HOP- A bouncing or up-and-down movement.

WHEEL SHIMMY- A side-to-side movement caused by dynamic imbalance.

WHEEL SPEED SENSORS- Magnetic pickups to detect wheel speed (used on anti lock braking systems).

WHEEL WEIGHT- Small pieces of lead that are clipped to the wheel rim to balance the wheel and tire combination.

WINDING- Loop or wire on a motor armature that generates a magnetic field.

WIRING DIAGRAM- Drawings that show relationships of components in an electrical circuit.

WIRING HARNESS- A group of primary wires enclosed in a protective plastic covering.

WORM SHAFT- Input gear in a recirculating ball gearbox.