TCC Repair 3.1L TS

Recently the TCC (Overdrive) clutch quit working on our '92 3.1L TS.

For now we have uncoupled the TCC socket on the transmission & it works fine but the mileage has gone down, especially for long trips.

Does anyone know how this can be repaired, is it necessary to disassemble the transmission for this or can it be accessed/replaced by taking down the pan/filter?

The TCC itself is located in the torque converter. The transaxle would need to be split from the engine to remove the converter.

The 1991 TranSport was likely the first year for the 4T60E transmission. That being the case, the only things accessible through the lower pan/cover are the 1-2 band servo, the 1-2/2-3 accumulators, and the filter. The control for the TCC is in the valve body behind the left side cover of the transmission.

http://www.wwdsltd.com/files/4T60SideCoverRemoved.jpg

TCC lockup/fallout was a common problem in the early series of this transmission after some age and mileage. You might find some details if you search for the TransGo K66908E or T84167E repair kit (https://transgo.com/product-details/sk-4t60e-jr/) designed specifically for this problem.

Short of removal and disassembly of the transmission, you could try to drain and refill the transmission witrh clean, fresh oil and a clean filter, then force the torque converter clutch to cycle on and off to exercise the valves and actuator. This is best done with the vehicle on a lift or stands, and by either wiring a switch to power the TCC solenoid or forcing the TCC with an older GM Tech II or similar bi-directional scanner.

That's an excellent piece of information BB!

Thank you for the picture/link - it's the most valuable lead I got on this issue.

Any idea on how much the mileage could drop due to TCC? Currently I disconnected the socket to prevent it from engaging at lower speeds and stalling the engine.