ASE T3 Drive Train (Medium/Heavy Truck) key terms

The small amount of pedal movement before the release bearing contacts the clutch fingers, allowing full clutch engagement and preventing slippage as parts wear or expand.

A bearing that rides on or near the clutch release fingers and converts pedal or linkage movement into axial force to disengage the clutch.

A small bearing in the end of the crankshaft that supports the forward end of the transmission input shaft, keeping it aligned with the clutch disc.

A mechanism that stops the transmission input shaft from spinning after the clutch is disengaged, allowing gears to mesh without grinding during a shift.

A conical, slotted steel spring in many clutches that presses the pressure plate against the disc; its finger tips are moved to release the clutch.

The shaft that carries engine torque from the clutch into the transmission; its front end is supported by the pilot bearing.

A shaft in a manual transmission, driven by the input shaft, that carries gears which transfer torque to gears on the main shaft.

The output-carrying shaft in a manual transmission on which the driven gears and synchronizers are mounted; it delivers torque to the driveline.

A hub-and-sleeve assembly that frictionally matches the speed of a gear to the main shaft before the shift sleeve engages its teeth.

A brass or steel ring in a synchronizer that creates friction and blocks the shift sleeve until gear and shaft speeds are close enough to engage.

A forked lever that slides a synchronizer sleeve or gear along a shaft when the driver or an actuator moves the shift rail.

A fluid coupling with an impeller, turbine, and stator that multiplies engine torque and drives an automatic transmission's input; it also cushions driveline shock.

A set of gears consisting of a sun gear, planet gears, and a ring gear that provides different ratios and direction changes when components are held or driven.

A hydraulic control block in an automatic transmission containing valves and passages that direct fluid pressure to apply clutches and bands for shifting.

An electronic controller that monitors speed, throttle, and other inputs to command shift solenoids, line pressure, and torque converter clutch operation.

A two-speed gear section behind the main gearbox in a compound transmission that provides a low and a high range, often shifted with a splitter or range valve.

A flexible coupling that transmits torque between shafts meeting at an angle, typically using a cross and bearing cups that allow the driveshaft to flex as the suspension moves.

A splined yoke that permits the driveshaft to change length as the axle moves, sliding on the transmission output shaft or a splined stub.

The alignment of universal joint yokes on a two-piece or multi-section driveshaft so their angles cancel vibration; yokes are usually installed in a specific relationship.

A support bearing, usually rubber-mounted, that carries the middle of a two-piece driveshaft and reduces vibration and sag while allowing slight flex.

A constant-velocity coupling made of two universal joints connected by a centering ball and socket, used where shaft angles are large and smooth power flow is needed.

The angle between the transmission output shaft and the driveshaft or between the driveshaft and axle pinion; incorrect angles cause vibration and joint wear.

A flange bolted to a shaft or yoke that provides a flat, bolted connection between the driveshaft and the transmission, axle, or center support.

The final-drive gear set in the axle; the pinion drives the larger ring gear to multiply torque and change driveshaft speed to axle speed.

The housing or assembly that holds the ring gear, differential case, spider gears, and pinion bearings and mounts into the axle housing.

A small bevel gear mounted on the differential cross shaft that allows the side gears, and therefore the two wheels, to turn at different speeds.

A bevel gear splined to an axle shaft inside the differential; it receives torque from the spider gears and turns the wheel.

The measured tightness applied to the pinion bearings by a crush sleeve, shims, or adjusting nut so the pinion rotates with controlled drag and stays stable under load.

The small clearance between the teeth of the ring gear and pinion, measured with a dial indicator, that allows lubricant film and prevents binding or noise.

A differential in a tandem axle assembly that lets the two axle assemblies turn at different average speeds while still dividing torque between them.

A mechanism that locks the differential case to a side gear or axle shaft, forcing both wheels to turn together for traction on slippery surfaces.

A device driven by the transmission or engine that supplies mechanical power to auxiliary equipment such as a hydraulic pump, winch, or blower.

A multi-plate clutch inside some PTO units that engages or disengages the auxiliary drive, often controlled by air or hydraulic pressure.

A condition where the PTO output spins faster than its rated limit, which can damage the PTO, pump, or driven equipment and may be prevented by interlocks.

A PTO arrangement that mounts between the transmission and differential, driving auxiliary equipment from the driveshaft line rather than the transmission side opening.