ASE S3 Drive Train (School Bus) flashcards

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

Overall gear ratio

The product of transmission gear ratio and axle ratio; determines final torque multiplication and wheel speed for a given engine speed.

Torque converter stall

The maximum engine speed reached with the output held stationary; converter multiplies torque at stall and slip decreases as speed rises.

U-joint operating angle

The angular difference between shaft centerlines at a joint; matched equal-and-opposite angles cancel velocity fluctuation and reduce vibration.

Final drive ratio

Ring gear teeth divided by pinion teeth; sets how many driveshaft turns occur per axle shaft turn.

Slip joint function

Allows the driveshaft length to change as the suspension moves, preventing binding and thrust loads on the transmission output.

Driveline power flow

Engine torque passes through clutch or converter, transmission, driveshaft, differential, and axle shafts to the wheels.

Road speed noise test

Noise that changes with vehicle speed points to driveline or axle; noise tied to engine speed points to engine or converter.

TCC slip data

Scan tool value comparing engine and transmission input speed; excessive slip indicates converter clutch or hydraulic fault.

Line pressure test

Measures hydraulic pressure in each range at idle and stall; low pressure causes slipping and delayed engagement.

Burnt fluid indicator

Dark fluid with a burnt smell indicates overheating and friction material breakdown, suggesting internal transmission damage.

Linkage adjustment check

Verify shift cable and lever alignment before internal diagnosis; misadjustment causes wrong range indication and no-start complaints.

Vibration on acceleration

Vibration that appears under load often indicates worn U-joints, loose mounts, or excessive driveline angle.

Clutch free play

Pedal travel before the release bearing contacts the pressure plate; too little causes slip, too much causes incomplete release.

Clutch slip symptom

Engine speed rises without matching vehicle speed under load; caused by worn friction disc, weak pressure plate, or oil contamination.

Release bearing noise

Noise heard when the clutch pedal is depressed and gone when released indicates a worn release bearing.

Pilot bearing function

Supports the transmission input shaft in the crankshaft; failure causes noise, vibration, and difficult shifting.

Clutch chatter cause

Judder during engagement from contaminated, warped, or glazed friction surfaces, or from loose engine or transmission mounts.

Hydraulic clutch bleeding

Removing air from the clutch hydraulic circuit restores full release travel; air causes a spongy pedal and hard shifting.

Stall test purpose

Brief full-throttle stall in each range checks converter and engine power; compare RPM to specification to find slip.

Shift solenoid fault

A failed solenoid causes harsh, delayed, or missing shifts; scan tool codes and live data confirm before teardown.

Fluid specification match

Using the manufacturer-specified automatic transmission fluid prevents shift quality and durability problems from incorrect friction characteristics.

Transmission cooler flow

Restricted cooler flow raises fluid temperature and shortens life; check for blockage and proper flow direction.

Severe duty interval

Stop-and-go school bus service may require shorter transmission fluid and filter intervals than the normal schedule.

Pressure control solenoid

Regulates line pressure electronically; failure can cause low pressure, slipping, or harsh engagement.

Ring and pinion ratio

Ring gear tooth count divided by pinion tooth count; verify ratio before ordering replacement gears.

Differential backlash

Small clearance between ring and pinion teeth measured with a dial indicator; incorrect setting causes noise and wear.

Pinion preload

Bearing load set by crush sleeve or shims; incorrect preload causes whine, heat, and premature bearing failure.

Gear contact pattern

Drive-side and coast-side tooth contact marks show mesh quality; pattern shifts reveal adjustment or wear problems.

Axle seal leak

Gear oil at the backing plate indicates a failed axle seal that can contaminate brakes and reduce stopping performance.

Driveshaft runout

Dial indicator measurement of shaft wobble; excessive runout indicates a bent shaft or worn yoke and causes vibration.

Center support bearing

Supports a two-piece driveshaft; a sagging or worn mount changes driveline angle and causes vibration.

First-order vibration

Vibration frequency matching driveshaft RPM; points to imbalance, runout, or U-joint problems in the shaft assembly.