Question : 4T60E lock-up problem

[Daniel-Rydholm]

Hi
I have a Buick Park Avenue in 1994. I have a problem with the lock-up does not work when the transmission reaches normal operating temperature. When it's cold it works perfectly. PCM goes into a protection mode when disconnecting the lock-up and 4 gear. I am forced to shut down and restart the engine to make it work again. I have changed all the shift solenoids and a new torque converter. But without result.

[robertisaar]

it is possible that at full temperature, your 4th gear clutches or TCC start slipping(either due to worn clutches or the TCC/TCC PWM solenoids/valves becoming sloppy), causing the PCM to kick into the protection mode. the TCC PWM valve getting sloppy and allowing apply fluid to bypass the TCC isn't that uncommon with later 4T60Es, I believe Sonnax released a kit that has an updated valve or sleeve or something along those lines.

[Daniel-Rydholm]

Okay, I have checked up Sonnax and it seems logical that it is the one that bothered. Has ordered a TCC Apply Valve Kit. Part No.84754-22K. Will be interesting to see if that helps

[rick444]

I had to make my engine run very smooth. Otherwise I got the same dropout oscillation chuggle fishbite trouble as you have, Turns out that I do not to fix transmission.
I defeated the egr to get engine smooth for a test. I probably have a lazy sensor or a slight vacuum leak or something a little hard to find.
Thats all, thanks.

[rick444]

Daniel
Did the sonnax valve kit fix the tcc slippage?

[Daniel-Rydholm]

Unfortunately, did not help sonnax kit. So now I have picked apart the whole transmission, to replace all gaskets and o-rings. I hope it'll help.

[rick444]

Well, I just changed the filter and some fluid and added some Lucas seal conditioner and that worked for me. My guess is that the 4th clutch piston seals lost their grip.
I think the swelling and softening of seals will maybe buy me some time and now I have my 4th and TCC that should return about 2 mpg.
In my past years I have done 3 trans; gm and two chrysler. Hardest part is pulling them out.
Now I am 69 yrs old and really find such work too difficult.
I am sorry that you went to all that trouble to remove the side cover. Ugh.
In retrospect, How bad was it? I was considering doing it myself.
In short, thanks for the reply.
Rick