94 GC Upshift Problem

A friend's 94 GC, 114,000 miles, had the overdrive unit internal to the trans fall apart. He had the entire trans rebuilt by a very reputable transmission man.

Now the Jeep isn't wanting to shift into 3rd some of the time.

This happened some before the rebuild but it's back now, When it shifts correctly it shifts well, if a little late with a higher than feels natural RPM.

The trans man said he had it scanned as part of his service and that it showed a TPS and an O2 sensor code.

We replaced the TPS as I know sensors just need to be replaced after awhile.

So now, he has a Jeep that won't go into 3rd but about half the time.

Ideas?

Thanks

I have read on other posts that Jeep owners should not use Dexron type transmission fluid even though the manuals recommend it. ATF should be used. After replacing the fluid, the computer needs to be reset. I recently learned this, but had been battling transmission problems for a few years -- since about the time I replaced the transmission fluid myself. The problems that I had sounded very similar to your friend's.

I had not been driving my 1996 Grand Cher. for about 9 months, until about 2 weeks ago. My transmission fluid continually leaks and was several quarts low. I bought ATF +3 as replacement. My battery also had died. The process of replacing the battery apparently reset the computer. The transmission now works as good as ever. Sometimes better to be lucky than smart. I will completely replace the Dexron fluid when it warms up a bit around here.

You might want to search this site for more detailed descriptions of resetting the computer and how to operate the vehicle to retrain it.

I have also read here about "retraining " the computer as explained in the service bullitin, but to start by disconecting the battery , and going thru many different shift patterns makes me question the validity of it , if that was the case , you d have to retrain the puter every time you disconect the batt for maintence!, im going to have the stealer ship re flash the puter , and hope theres upgrades for it after 10 years