Manual Drive Train and Axles A3 Flashcards

A manual transmission grinds when shifting into 3rd gear but shifts smoothly into all other gears. The synchronizer ring for 3rd gear is suspected. What does the synchronizer do?

Answer: Matches the speed of the gear to the main shaft before engagement

A synchronizer ring matches (synchronizes) the rotational speed of the gear being selected to the speed of the main shaft through friction. If the synchronizer is worn and cannot equalize speeds quickly enough, the dog teeth grind during engagement.

A technician is checking a four-wheel-drive transfer case and finds the chain stretched beyond specification. What symptoms would the driver most likely report?

Answer: A slapping or rattling noise from the transfer case during acceleration and deceleration

A stretched drive chain in a transfer case creates excessive slack, which causes a slapping or rattling noise as the chain alternately tightens under load and goes slack during deceleration. This noise is often confused with engine valve train noise but is located under the vehicle.

During a CV axle boot inspection, a technician finds the outer boot is cracked and has thrown grease onto the inside of the wheel well. What is the MOST important next step?

Answer: Inspect the CV joint for wear and damage before deciding on repair

Before deciding on repair, the CV joint must be inspected for contamination and wear. If the boot has been cracked and throwing grease, dirt and water may have entered the joint. A contaminated or damaged joint requires axle replacement, while an undamaged joint may be repaired with a boot kit.

A rear-wheel-drive vehicle with a solid rear axle exhibits a clunking noise only on initial acceleration from a stop and not during driving. What is the MOST likely cause?

Answer: Excessive ring and pinion backlash in the differential

A single clunk on initial acceleration from rest indicates excessive backlash in the ring and pinion gear set. The free play in the gear mesh allows the pinion to snap against the ring gear when torque is first applied, producing a single clunk rather than a continuous noise.

When performing a clutch replacement, a technician notices the flywheel friction surface has slight heat cracks (heat checks) but is within the resurfacing specification. Should the flywheel be resurfaced?

Answer: Yes, heat cracks indicate metal stress and the surface should be resurfaced or replaced

Heat cracks in a flywheel indicate surface stress from overheating. While they may be within thickness specification for machining, the cracked surface will cause uneven clutch engagement, accelerated disc wear, and potential future cracking. Resurfacing is the correct action to restore a smooth, flat friction surface.

A limited-slip differential (LSD) equipped vehicle exhibits chattering during low-speed turns. What is the MOST likely cause and correct fix?

Answer: Incorrect gear oil — standard hypoid gear oil used instead of friction modifier additive

LSD chatter during low-speed turns is a classic symptom of incorrect gear oil. LSDs require friction modifier additive in the gear oil to properly lubricate the clutch packs. Standard hypoid gear oil without friction modifier causes the clutch discs to grab and release rapidly, producing the chattering noise.