Automotive and Mechanics Transmission & Drivetrain 2 — Questions and Answers
Question 1: What does a limited-slip differential (LSD) do compared to an open differential?
- Locks both wheels rigidly together at all times
- Transfers more torque to the wheel with better traction when slip is detected (Correct answer)
- Reduces driveshaft speed
- Eliminates the need for a differential entirely
Correct answer: Transfers more torque to the wheel with better traction when slip is detected
An LSD uses clutch packs or a Torsen gear set to bias torque toward the wheel with more traction, improving performance on slippery or uneven surfaces.
Question 2: What is the purpose of the transmission valve body?
- Filter transmission fluid
- Direct hydraulic fluid pressure to actuate clutch packs and bands for gear changes (Correct answer)
- Regulate torque converter pressure only
- Cool the transmission fluid
Correct answer: Direct hydraulic fluid pressure to actuate clutch packs and bands for gear changes
The valve body is the hydraulic control center of an automatic transmission, routing pressurized fluid to the correct clutch packs and bands to engage each gear.
Question 3: What is a CV (constant velocity) joint used for?
- Connect the driveshaft to the differential in rear-wheel-drive vehicles only
- Transmit torque at a constant rotational speed through a varying angle, used in front-wheel-drive axles (Correct answer)
- Reduce driveshaft vibration on straight-line applications
- Replace the u-joint in high-torque applications only
Correct answer: Transmit torque at a constant rotational speed through a varying angle, used in front-wheel-drive axles
CV joints allow axle shafts to transmit smooth, constant-velocity torque to the front wheels while accommodating the up-and-down and steering angle changes.
Question 4: What symptom indicates a failing outer CV joint?
- Vibration at highway speeds
- Clicking or popping noise during turns (Correct answer)
- Grinding noise when braking
- Whining noise in reverse
Correct answer: Clicking or popping noise during turns
A worn outer CV joint typically produces a clicking or popping noise during turns because the ball-and-groove contact deteriorates, causing the joint to bind under angle.
Question 5: What is transmission line pressure and why is it important?
- The cooling system pressure inside the radiator
- Hydraulic pressure supplied by the transmission pump that controls clutch pack engagement force (Correct answer)
- The pressure inside the torque converter only
- The fluid pressure at the filter inlet
Correct answer: Hydraulic pressure supplied by the transmission pump that controls clutch pack engagement force
Line pressure is the main hydraulic pressure developed by the transmission pump and controls how firmly clutch packs engage, affecting shift quality and durability.
Question 6: What is the role of the transmission range sensor (TR sensor) or neutral safety switch?
- Measure transmission fluid temperature
- Inform the ECU of gear selector position and prevent starter engagement in gear (Correct answer)
- Control torque converter lockup
- Monitor transmission output shaft speed
Correct answer: Inform the ECU of gear selector position and prevent starter engagement in gear
The TR sensor tells the ECU which gear range is selected and prevents the starter from cranking in Drive or Reverse, protecting against accidental engagement.
Automotive and Mechanics Transmission & Drivetrain 2
What does a limited-slip differential (LSD) do compared to an open differential?