Automatic Transmission Systems Flashcards

A vehicle has very poor acceleration from a stop but drives normally at highway speed. Which torque converter fault fits best?

Answer: Stator one-way clutch freewheeling in both directions

If the stator can't hold, there is no torque multiplication at low speed, but coupling-phase operation stays normal.

A stator one-way clutch that is seized (locked in both directions) typically causes what symptom?

Answer: Poor high-speed performance and fluid overheating

A locked stator interferes with fluid flow during the coupling phase, which limits top speed and creates heat.

A shudder at 40-50 mph under light throttle happens only when the TCC applies. What is a common first repair step?

Answer: Drain and refill with the specified fluid that has the correct friction modifiers

Degraded or incorrect fluid often causes TCC shudder, and a fluid exchange with the correct fluid is a common fix.

A torque converter multiplies torque the most under which condition?

Answer: Turbine speed much lower than impeller speed

Maximum torque multiplication happens near stall, when the speed difference between impeller and turbine is greatest.

When performing a stall test, about how long should the throttle be held wide open?

Answer: No more than about 5 seconds

Holding stall more than about 5 seconds can overheat the fluid and damage the converter and clutches.

During a stall test in Drive, stall rpm is well above specification. What does this most likely indicate?

Answer: Slipping clutch or band applied in that range

High stall speed means a holding member is slipping and letting the engine rev too high.

The PCM/TCM usually applies the torque converter clutch under which conditions?

Answer: Warm engine, steady cruise above a set speed

TCC lockup is commanded at steady cruise with a warm engine to remove converter slip and improve fuel economy.