hello all i have a 1994 cutlass convertible 3.1 w/4t60e trans,i bought it 2 years ago after about 3 months one day it started shifting from overdrive into drive after it warmed up to operating temp, never really hurt nothing except for fuel mpg, well i drove it till the trans went out thinking it was to blame that was about 2 months ago so got another one and swapped it out thinking it would cure it,well this trans does the same thing i know its possible for 2 to do the same thing considering these trans aren't the best gm ever made, the engine light isn't on no codes come back,leads me to believe it is the computer has a bad cell,has anyone had this problem before or heard of it?

Welcome to AF.

What type of scan tool are you using ??
Not all scanners can read all codes, especialy trans and chassis DTC's.

But it sounds like a wire harness problem, possibly the ground shorting out causing your constant shifting.

First thing I would do is get it scanned with a trans/ABS capable scan tool and see if thiers any codes.
Then inspect the main harness, it is burried.

Seen this on a few tranys back in the day.
GM's fix was black tape.
Which just fell off, or rubbed through, and shorted again making the customer come back again and again, untill the trans crapped out. :rolleyes:

hope that helps.

thanks for the message will have to check the harness,guess it can't hurt,your talking about the main harnesses that plug in am definatly thinking electrical of some sort,because the old trans that went out did it and the one i just installed does it too,do u think its possible if it isn't the wiring harness,that the computer could have a problem

A scan for transmission codes wouldnt hurt.
I know I've seen these models with which the wires were scraped and damaged causing the continuos up/down shifting.
Could even be right where the wires go into the trans, or somewhere that they could have rubbed through the case.