picked up a 96 to tinker on, seems to run good except when shifting into O/D and the only way to get it to shift is to let off the gas then when it shifts the car just goes to idling rpm if I give it gas it just rev's if I turn off the O/D using the button it will then shift back down where the car will power it self again.

Any thoughts what might cause this

 

You do realize that when you turn O/D off, you won't see 4th gear and remain in 3rd.

 

which is why I said when I turn off overdrive is the only way I can get it back into gear when overdrive is ON it tries shifting to 4th only if I let off the throttle and its like it shifts into neutral at that point car will just rev or go down to idle so then have to turn off overdrive using the button to get it back into 3rd so the car will accelerate

 

Sounds like 4th gear is gone. If you just leave it in D and accelerate, does the transmission attempt to shift all the way through or does it only shift 1-2-3 and remain there?

 

its try's shifting 1-2-3-4 but when it hits forth its like you shifted to neutral