theres a problem with the tranny on my 90 sse . it doesnt shift into overdrive at all. everything else works fine shifts smooth and everything it never worked since i got the car. i dont really do a lot of highway driving so its not tha big of a problem but it kinda bothers me that its broken. i had a guy look at it but all he said was that it could be something stupid or it could cost a lot of money. i dont want rip it apart until i know what what know what im getting myself into.. so my question is: is this a common problem with these cars? and what could it be the cause? if anyone knows itll be you guys

On my 90 the TCC does not engage until 48-50 mph and the coolant temp must be over 150F. At 55 the engine should be turning about 1500 rpm and will change very slowly (70 mph = 2000 rpm) if you accelerate mildly. If not locked the tack will be around 2k and will jump when you accellerate.

TCC not locking is not a big thing, drove a Fiero for about 50,000 miles that never locked up but is good to know why. Besides the coolant temp (will also keep the engine from going into closed loop if too low) certain error codes can also block.