I have a 95' Trans Am with a 4l60e, has a 3600 vigilante converter rebuilt last year and when i start it and its cold, converter locks up fine, when it warms up, once it unlocks, it stays unlocked. What could it be? Been chasing this for about a year and no luck?

 

Did the problem start when the converter was installed . I find the best way to diagnose this is to use a Dealer Tech2 and under special functions do a manual TCC test both cold and hot . While observing trans temp , slip speed , release pressure,Duty Cycle , Brake switch function etc. then do a snap shot at approx. the temp that it stops working. This an electronic picture of what happens when or if TCC is applied. Did it set any codes etc.