310T Drive Train Systems 2 — Questions and Answers
Question 1: A heavy-duty truck experiences a vibration that increases with vehicle speed but is NOT affected by engine RPM. The MOST likely cause is:
- Worn engine mounts
- Driveshaft imbalance or worn U-joints (Correct answer)
- Faulty torque converter
- Worn clutch disc
Correct answer: Driveshaft imbalance or worn U-joints
A speed-related vibration independent of engine RPM points to the driveshaft or U-joints rather than engine components.
Question 2: Which type of differential is BEST suited for a drive axle that regularly operates on slippery surfaces?
- Open differential
- Inter-axle differential
- Limited-slip differential (Correct answer)
- Spur gear differential
Correct answer: Limited-slip differential
A limited-slip differential transfers more torque to the wheel with better traction, improving performance on slippery surfaces.
Question 3: When checking driveshaft working angles, the front and rear U-joint angles should be:
- Equal and in opposite phase (Correct answer)
- Unequal and in phase
- Equal and in phase
- Unequal and in opposite phase
Correct answer: Equal and in opposite phase
Equal but opposing working angles cancel out velocity fluctuations and prevent vibration in the driveline.
Question 4: A manual transmission jumps out of a high gear under load. The MOST probable cause is:
- Worn synchronizer blocking rings
- Worn shift fork or detent springs (Correct answer)
- Low transmission oil level
- Incorrect clutch adjustment
Correct answer: Worn shift fork or detent springs
Worn shift forks or weak detent springs allow the synchronizer sleeve to slide back out of engagement under load.
Question 5: In a tandem drive axle arrangement, the purpose of the inter-axle differential (power divider) is to:
- Allow speed differences between left and right wheels on one axle
- Distribute torque equally between the front and rear drive axles (Correct answer)
- Lock both axles together permanently for off-road use
- Reduce torque multiplication from the main transmission
Correct answer: Distribute torque equally between the front and rear drive axles
The inter-axle differential allows the two drive axles to rotate at different speeds while splitting torque between them.
Question 6: What does a higher numerical axle ratio (e.g., 4.56:1 vs. 3.73:1) provide?
- Higher top speed with lower torque multiplication
- Lower top speed with higher torque multiplication (Correct answer)
- No change in vehicle performance
- Better fuel economy at highway speeds
Correct answer: Lower top speed with higher torque multiplication
A higher numerical gear ratio provides greater torque multiplication at the wheels but limits top speed.
Question 7: A technician notices the clutch pedal has very little free play. What is the MOST likely result if this condition is ignored?
- Difficulty engaging gears
- Premature clutch disc wear and slipping (Correct answer)
- Excessive noise during gear shifts
- Transmission oil contamination
Correct answer: Premature clutch disc wear and slipping
Insufficient free play keeps the release bearing partially loaded against the pressure plate, causing the clutch to slip and wear prematurely.
310T Drive Train Systems 2
A heavy-duty truck experiences a vibration that increases with vehicle speed but is NOT affected by engine RPM.
The MOST likely cause is: