RANDOM OVERDRIVE PROBLEM
 

1995 BONNEVILLE SE

I had a used transmission put into my car two months ago and had intermittent problems where it wouldn't shift into overdrive. I would pull off the road and turn the car off and start back up and the overdrive would work again.

I read about problems with the TCC selenoid or valve body cross leaking on this forum so I told the transmission guy to install another transmission in my car because there was a problem with the one he put in.

I just received my car again whith another transmission in it (from a wreck, but in good shape) and it worked well for two days. Now it's starting to have the same problem where sometimes it won't shift into overdrive. I think it's mainly when the car is warmed up.

I know it's not the transmission now, could it be the PCM?

Anyone have any ideas what would cause this, the electrical connections are clean.

Thanks for any info ....

There was a GM service bulletin about a similar TCC problem, and the cause of the problem was a chafed wire in the harness that connects to the tranny...but that problem was only documented for the '91-'93 4T60-E transmission. To fix that problem, the wiring harness needed to be replaced.

Both my friend Phil's 1995 SLE and my 1994 SLE have this same problem.
So, swapping the Supercharged 1993 Park Avenue Ultra's tranny into my 1994 won't solve the problem?
How hard is it to change the harness?
Buy new from GM or get one from a salvage yard?

I hear everyone talking about scan tools .... can I buy one somewhere and do it myself?
I'm quite mechanical but I don't have any of these speciality tools like scanners. If I can get one for a reasonable price, how much would one cost and what is a good make/model to get for my 95 bonny se?

If the problem turns out to be the PCM, where is it located and how much is a replacement? Also I hear people talking about replacing some chip or module which gives you better performance. Can you give me some info on that as well? Maybe a price and model to purchase.

Thanks again......