ASE T3 Drive Train (Medium/Heavy Truck) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Clutch free play

Clearance between release bearing and clutch spring; prevents bearing contact when engaged; too little causes slip, too much causes incomplete release.

Diaphragm spring clutch

Belleville-type spring applies clamp load to pressure plate; release bearing pushes fingers inward to disengage; worn fingers reduce capacity.

Clutch brake function

Friction device applied near bottom of pedal travel to stop transmission input shaft; allows gear engagement in non-synchronized heavy truck transmissions.

Clutch slippage diagnosis

If engine speed rises without vehicle speed under load and free play is correct, suspect worn friction disc, weak pressure spring, or oil contamination.

Pilot bearing role

Supports nose of transmission input shaft in flywheel; seizure or misalignment causes input shaft drag, hard shifting, and clutch drag.

Clutch torque capacity

Approximate capacity equals friction coefficient times clamp load times number of friction surfaces times mean radius; heat and wear reduce actual capacity.

Clutch chatter causes

Engagement vibration often from oil on disc, warped flywheel, loose engine mounts, worn release bearing, or misaligned bell housing.

Synchronizer function

Friction cones speed up or slow the gear before the shift collar locks; worn blocker rings cause clash when shifting.

Range shift operation

Auxiliary planetary range box provides high and low ranges; air shift must occur in neutral with correct pressure to avoid gear damage.

Splitter shift

Splitter divides each main gear into two ratios; operates under load in some designs; must match engine speed and air pressure.

Torque converter stall

At zero output speed converter multiplies engine torque; stall test compares engine and converter condition; limit duration to avoid overheating.

Converter lockup clutch

Locks turbine to impeller at road speed to eliminate slip, reduce heat, and improve fuel economy; disengages during shifts.

Automatic pressure test

Measures hydraulic pressure at test ports in each range; low pressure causes slip and burned clutches; compare to specification at idle and stall.

AMT clutch calibration

Automated manual transmission uses actuators and ECU; clutch wear calibration sets engagement point; incorrect calibration causes harsh engagement or slip.

U-joint phasing

Yokes at both ends of a driveshaft must align in phase; incorrect phasing creates twice-per-revolution speed variation and vibration.

Equal joint angles

For a two-joint shaft, angles at each end should be equal and opposite within specification to cancel velocity fluctuation and prevent vibration.

Slip joint purpose

Splined slip yoke changes driveshaft length as suspension moves; binding or lack of grease causes thrust loads and vibration.

Center bearing function

Supports intermediate driveshaft section; worn rubber insulator or bearing misalignment causes vibration, especially during acceleration.

Driveshaft critical speed

Maximum safe rotational speed depends on length, diameter, and mass; exceeding it causes whipping and potential shaft failure.

U-joint seizure symptom

A seized universal joint cannot articulate smoothly; it causes cyclic vibration, abnormal noise, and can fracture the yoke or shaft.

Gear ratio calculation

Divide ring gear tooth count by pinion tooth count; higher numeric ratio increases torque multiplication and reduces road speed for given engine speed.

Differential function

Allows left and right wheels to turn at different speeds while transmitting torque; spider gears rotate when wheels differ in speed.

Hypoid gear lubricant

Hypoid ring and pinion require API GL-5 lubricant; limited-slip differentials may also need friction modifier to prevent chatter.

Interaxle differential lock

Locks tandem axle power divider for traction; disengage on high-traction surfaces to avoid driveline windup and tire wear.

Pinion bearing preload

Established with shims or collapsible spacer; too little allows pinion movement and noise; too much causes bearing overheating and failure.

Gear contact pattern

Gear marking compound shows tooth contact; pattern indicates pinion depth and backlash adjustment; incorrect pattern causes noise and rapid wear.

PTO output speed

Depends on engine speed, PTO drive ratio, and whether driven by transmission gear; calculate using engine RPM divided by ratio.

Transmission-mounted PTO

Driven by a transmission power take-off gear; output speed changes with selected transmission gear and requires lubricant from gearbox.

Air-shift PTO

Engages with air pressure through solenoid valve; low pressure or electrical fault prevents engagement and may cause gear clash.

PTO duty cycle

Intermittent PTO cannot run continuously at full torque; exceeding duty cycle overheats oil and damages gears or bearings.

PTO safety interlock

Prevents engagement unless transmission is in neutral and parking brake applied; bypassing interlock can allow unexpected vehicle movement.

Auxiliary hydraulic pump drive

PTO-mounted pump supplies hydraulic flow proportional to engine speed; relief valve limits pressure and protects pump and circuit.