ASE T3 Drive Train (Medium/Heavy Truck) study guide
ASE T3 Drive Train (Medium/Heavy Truck) · Work through your exam, one topic at a time.
ASE T3, Drive Train, is the medium/heavy truck certification test that covers the hardware that carries engine torque from the flywheel to the wheels of a commercial vehicle. It is written for working technicians - fleet shop hands, dealership driveline and axle specialists, and independent heavy-truck mechanics - who already diagnose and repair clutches, gearboxes, driveshafts, rear axles and power take-off systems on the job, and who want third-party proof of that skill for employers, insurers, or their own career plan. The ASE T3 Drive Train (Medium/Heavy Truck) study guide has 5 sections and about 1,792 words.
01Clutch System: Operation, Adjustment, and Diagnosis
Heavy-truck clutches are dry, single- or double-disc units bolted to the flywheel. In a push-type clutch the release bearing pushes the release fingers or diaphragm toward the flywheel to release the discs; in a pull-type clutch the bearing pulls a release sleeve rearward.
385 words, about 2 min02Manual and Automatic Transmissions
Non-synchronized, constant-mesh boxes (9-, 10-, 13-, 18-speed) use sliding clutch collars to lock gears to the mainshaft, so shifting depends on matching engine and mainshaft speed. The clutch brake is used only when starting from a standstill.
391 words, about 2 min03Driveline and Universal Joints
A single-Cardan U-joint produces a small cyclic speed change, so each shaft has two joints whose operating angles must be equal and opposite (within roughly 1/2 degree) so the fluctuations cancel. The yokes on a shaft must be in phase - ears at both ends parallel - unless the OEM specifies otherwise for a two-piece shaft with a CV or center bearing.
331 words, about 2 min04Drive Axles and Differentials
The carrier houses the pinion, ring gear, differential case with side gears and spider gears, and bearings set with preload. Single-reduction hypoid axles are most common; two-speed and planetary double-reduction axles also exist.
334 words, about 2 min05Power Take-Off and Auxiliary Drive Components
A PTO takes power from a transmission aperture (side, top, or rear) or from the engine through a front gear train (REPTO). Most light-duty truck PTOs are countershaft driven : they turn whenever the clutch is engaged, so during stationary operation the transmission must be in neutral with the clutch engaged, the parking brake set, and the wheels chocked.
351 words, about 2 min