NCED Transmission & Drivetrain Systems 2 — Questions and Answers
Question 1: What is the primary function of a torque converter in an automatic transmission?
- To lock the transmission into a fixed gear ratio
- To transfer engine torque to the transmission while allowing slip during low speeds (Correct answer)
- To regulate hydraulic pressure throughout the transmission
- To engage and disengage the transmission from the driveshaft
Correct answer: To transfer engine torque to the transmission while allowing slip during low speeds
A torque converter uses fluid coupling to transfer engine torque to the transmission, allowing the vehicle to remain stationary with the engine running.
Question 2: Which component in a manual transmission synchronizes the speeds of the gear and shaft before engagement?
- Clutch disc
- Synchro ring (synchronizer) (Correct answer)
- Shift fork
- Countershaft
Correct answer: Synchro ring (synchronizer)
Synchronizer rings match the rotational speed of the gear to the shaft before teeth engage, preventing grinding.
Question 3: A continuously variable transmission (CVT) achieves different gear ratios using:
- Planetary gear sets and hydraulic clutches
- A belt or chain running between two variable-diameter pulleys (Correct answer)
- Electronically controlled friction discs
- A series of fixed helical gears
Correct answer: A belt or chain running between two variable-diameter pulleys
CVTs use a belt or chain between two pulleys whose effective diameters change continuously, providing an infinite range of ratios.
Question 4: In an all-wheel drive (AWD) system, what is the role of the center differential?
- It converts two-wheel drive to four-wheel drive on command
- It distributes torque between front and rear axles while allowing speed differences (Correct answer)
- It locks both axles to the same rotational speed at all times
- It controls individual wheel braking during traction loss
Correct answer: It distributes torque between front and rear axles while allowing speed differences
The center differential allows front and rear axles to rotate at different speeds during cornering while still transmitting power to both.
Question 5: Which seal in an automatic transmission is most likely to cause external fluid leaks at the rear of the transmission?
- Pump seal
- Rear output shaft seal (Correct answer)
- Valve body gasket
- Torque converter seal
Correct answer: Rear output shaft seal
The rear output shaft seal prevents transmission fluid from leaking where the driveshaft exits the transmission case.
Question 6: What does 'gear hunting' or 'shift busyness' in an automatic transmission typically indicate?
- Worn clutch packs causing slippage
- A faulty transmission speed sensor or throttle position sensor signal (Correct answer)
- Contaminated fluid preventing fluid pressure buildup
- A broken planetary carrier preventing ratio changes
Correct answer: A faulty transmission speed sensor or throttle position sensor signal
Erratic or repeated shifting (hunting) usually stems from bad sensor inputs causing the TCM to misjudge the optimal gear.
Question 7: What is the purpose of a limited-slip differential (LSD) compared to an open differential?
- It eliminates the need for a ring and pinion gear set
- It biases torque toward the wheel with more traction instead of the spinning wheel (Correct answer)
- It allows both wheels to spin freely at all times
- It locks the axle shafts together permanently for off-road use
Correct answer: It biases torque toward the wheel with more traction instead of the spinning wheel
An LSD uses clutch packs, gears, or viscous fluid to transfer more torque to the wheel that has grip rather than the one that spins freely.
NCED Transmission & Drivetrain Systems 2
What is the primary function of a torque converter in an automatic transmission?