Automatic Transmission and Transaxle A2 Flashcards

A late-model vehicle with an electronically controlled automatic transmission sets a code for an incorrect gear ratio. The transmission shifts into all gears but feels like it is in the wrong gear at certain times. What should the technician check FIRST?

Answer: Verify the input and output speed sensor readings are accurate

An incorrect gear ratio code is set when the TCM calculates that the ratio between input shaft speed and output shaft speed doesn't match what's expected for the commanded gear. Verifying speed sensor accuracy is the logical first step before condemning solenoids or the TCM.

When adjusting a transmission band, a technician tightens the band adjusting screw to the specified torque, then backs it off a specified number of turns. What is the purpose of this adjustment?

Answer: To set the correct running clearance between the band and drum

Band adjustment sets the correct clearance (free play) between the band friction material and the drum. Tightening to specification and backing off a set number of turns establishes the proper gap, ensuring the band applies and releases correctly without dragging.

A vehicle with an automatic transmission has a shudder during torque converter clutch (TCC) engagement at highway speeds. What is the MOST likely cause?

Answer: Worn torque converter clutch friction material or contaminated fluid

TCC shudder during lockup clutch engagement is typically caused by worn or glazed torque converter clutch friction material, or by contaminated fluid that reduces the coefficient of friction. The clutch cannot engage smoothly and chatter-vibrates during the apply phase.

When replacing a transmission oil pump, what clearance measurement is MOST critical to verify before installation?

Answer: Gear-to-body side clearance and gear tip-to-crescent clearance

Transmission pump clearances — specifically the gear side clearance and tip-to-crescent clearance — determine the pump's ability to build and maintain hydraulic pressure. These measurements must be within specification to ensure proper pump output.

A front-wheel-drive vehicle with a transaxle vibrates excessively during acceleration from a stop. The vibration goes away when the accelerator is released. What should be inspected FIRST?

Answer: The engine and transmission mounts

Torque-sensitive vibration — present during acceleration and absent during coasting — is a classic symptom of worn or broken engine/transmission mounts. Under acceleration, engine torque causes movement that a deteriorated mount cannot dampen, transmitting vibration to the chassis.

An automatic transmission cooler line fitting is leaking at the transmission case. After tightening the fitting, it still leaks. What is the MOST appropriate repair?

Answer: Replace the threaded fitting boss in the case using a thread insert kit

When a transmission case cooler line fitting continues to leak after tightening, the aluminum case threads are likely stripped or damaged. Installing a thread insert (such as a Helicoil) restores the thread integrity and provides a proper sealing surface without replacing the entire case.