310S Drivetrain and Transmission 4 — Questions and Answers
Question 1: What is the purpose of the transmission valve body?
- To store transmission fluid
- To direct hydraulic fluid flow through a series of valves and passages to control clutch application, shift timing, and line pressure (Correct answer)
- To cool the transmission fluid
- To connect the torque converter to the transmission
Correct answer: To direct hydraulic fluid flow through a series of valves and passages to control clutch application, shift timing, and line pressure
The valve body is the hydraulic control centre of an automatic transmission. It contains numerous spool valves, check balls, and fluid passages that direct pressurized ATF to apply and release clutch packs and bands in the correct sequence.
Question 2: What does the ring and pinion gear ratio in a differential determine?
- The maximum vehicle speed only
- The final drive torque multiplication and the relationship between driveshaft speed and axle speed (Correct answer)
- The shift points of the transmission
- The turning radius of the vehicle
Correct answer: The final drive torque multiplication and the relationship between driveshaft speed and axle speed
The ring and pinion ratio (e.g., 3.73:1) determines how many times the driveshaft rotates for each revolution of the axle. A numerically higher ratio provides more torque multiplication but lower top speed, and vice versa.
Question 3: What is the purpose of the clutch pilot bearing (pilot bushing)?
- To support the clutch pedal mechanism
- To support and centre the front end of the transmission input shaft in the crankshaft (Correct answer)
- To release the pressure plate from the clutch disc
- To reduce clutch pedal effort
Correct answer: To support and centre the front end of the transmission input shaft in the crankshaft
The pilot bearing is pressed into the end of the crankshaft and supports the front tip of the transmission input shaft, keeping it centred and aligned with the crankshaft. A worn pilot bearing causes noise when the clutch pedal is depressed at idle.
Question 4: What is the function of the accumulator in an automatic transmission hydraulic circuit?
- To store extra transmission fluid
- To cushion the application of a clutch pack by temporarily absorbing hydraulic pressure, providing smooth shift engagement (Correct answer)
- To increase line pressure during heavy loads
- To filter debris from the transmission fluid
Correct answer: To cushion the application of a clutch pack by temporarily absorbing hydraulic pressure, providing smooth shift engagement
Accumulators use a spring-loaded piston in a bore to temporarily absorb some of the apply pressure during a shift, cushioning the engagement of the clutch pack for a smooth, controlled shift feel.
Question 5: What causes a clutch to chatter during engagement?
- Excessive clutch pedal free play
- Oil contamination on the clutch disc, warped disc or flywheel, worn disc damper springs, or loose engine/transmission mounts (Correct answer)
- A worn throw-out bearing
- Incorrect transmission fluid
Correct answer: Oil contamination on the clutch disc, warped disc or flywheel, worn disc damper springs, or loose engine/transmission mounts
Clutch chatter is a grabbing/vibrating sensation during engagement. Common causes include oil or grease on the friction surfaces, a warped or heat-checked flywheel, a warped clutch disc, broken disc damper springs, or loose mounts.
Question 6: What is the purpose of the speed sensor(s) on an automatic transmission?
- To monitor transmission fluid temperature
- To provide the TCM with input and output shaft speed data for calculating gear ratio, shift timing, and detecting slippage (Correct answer)
- To activate the backup lights
- To measure torque converter pressure
Correct answer: To provide the TCM with input and output shaft speed data for calculating gear ratio, shift timing, and detecting slippage
Input (turbine) and output speed sensors provide the transmission control module (TCM) with rotational speed data. The TCM calculates the actual gear ratio, commands shifts at proper points, and detects clutch slippage by comparing the two speeds.
310S Drivetrain and Transmission 4
What is the purpose of the transmission valve body?