93 4t60-E TCC issues

[Tim's Buick]

Hello all, I just joined. I'm a mechanic, and I specialize in general auto repair covering all kinds of things.

I have a 93 Park Avenue with the 3.8 and a 4T60-E. This is the second unit for this car. This time, I have a problem with the TCC. In the morning, when temps are cold, the TCC works like it regularly does, applying at 60, and then at 70 kph, 4th gear comes in. I do notice a bit of the shudder that they're known for as in TCC slipping, but it stays locked. After the car warms up, TCC is gone. After a little highway cruising, the transmission goes into third like the pcm is programed to do. Sounds really stupid.

I have confirmed it is transmission related and not anything to do with the PCM or wiring as confirmed with a scantool and testing of my wiring. I read a TSB on the TCC PWM valve and how they updated that valve with screens to prevent debris from getting into the valve. I pulled the side case off and replaced the TCC PWM and the TCC apply valve. Didn't fix the issue. I did some research and found this.

http://www.sonnax.com/parts/2549#tabs1-instructions

This describes my condition, and I wonder if I can get time to yank the tranny and do this repair?

For now, I rigged a switch on my dash to turn 4th gear on when I am on the highway cruising to save my gas and wear and tear on the motor. Kinda hard driving with third at 100 an hour.

Does anyone have any advice? I don't get into a whole lot of transmission or engine repairs really, but if its a simple fix that my local tranny shop can do, then I'm all for it VS a 1500 dollar rebuild.

Thanks!

[JerryRigg]

I had a similar issue with the first transmission my 95 GP with a 4T60-E. TCC would lockup when cold but then not at all when warm.

I ended up clipping the PWM wire. It solved the lack of lockup, although lockups were a little more abrupt.
In the end I had other unrelated trans issues that necessitated replacement, I grabbed one from a 1997 model, and the TCC works correctly with the PWM wire attached.