Reference Manual

Chapter 2: Transmissions: Torque Converter Clutch Operation


The Transmission / Transaxle Converter Clutch (TCC) System uses a solenoid operated valve in the automatic transmission to couple the engine flywheel to the output shaft of the transmission/transaxle through the torque converter. This reduces the slippage losses in the converter, which increases fuel economy.


For the converter clutch to apply, two conditions must be meet:

The ECM controls the TCC apply solenoid by looking at several sensors:

On some transmissions/transaxles, a third gear switch (normally open) is placed in series on the battery side of the TCC solenoid. This switch prevents TCC application until the transmission/transaxle is in third gear and then the switch closes, completing the circuit to the ECM.

Also some transmissions/transaxles use a 4-3 pulse switch (or 3-2 on some 3 speed transmissions/transaxles), to open the TCC solenoid circuit momentarily during a downshift.

Results of Incorrect TCC Operation

If the converter clutch is applied at all times, the engine will stall immediately, just as in a manual tranmission/transaxle with the clutch applied.

If the converter clutch does not apply, fuel economy may be lower than expected. If the Vehicle Speed Sensor fails, the TCC will not apply. If the 3rd or 4th gear switch does not operate, the TCC will not apply at the right time.

The Transmission/transaxle Converter Clutch (TCC) system has different operating characteristics than an automatic transmission without TCC. If the driver complains of a "chuggle" or "surge" condition, the car should be road tested and compared to a similar car to see if a real problem exists. Another TCC complaint may be a downshift felt when going up a grade, especially with cruise control. This may not be a downshift, but a clutch disengagement due to the change in TPS to maintain cruising speed.

Table of Contents Top of Chapter

Copyright © 1998-2023 by The Members of The Oldsmobile Mailing List. All Rights Reserved. This web site is not affiliated with General Motors or Oldsmobile. General Motors and Oldsmobile are trademarks of their respective companies. The owners and members of this site are not responsible for errors or inaccuracies.