My buddies story:

98 Firebird v6 swapped a ls1 and 4l60e in. This car has given him problems overtime. Lots of leaks, squeaks, etc. Lately his tranny has been acting up. Overdrive only works "sometimes" but only when its cold. After that, it doesn't work anymore. 1st, 2nd and 3rd work fine. Tranny fluid is at the proper level. One of my buddies installed the tranny for him. Is there something that wasn't set up properly when he put it in? The tranny is supposed to have good parts in it, and he got it from a member on this board. Can anyone shed some light to my buddy? Thanks for any help.

If anyone needs anymore info, just let me know and I'll relay it. He currently doesn't have a computer.

 

I would scan for codes first and go from there.

 

That will be the first thing we try. Thanks for the help, I'll reply with more when we get to this soon.

 

Be sure the plug on the side of the transmission is plugged in all the way till it snaps.
Do the codes, if you have more than one it still could be the connector.
Don't ask me how I know. (:

 

Thanks for the help, I will also try that. My buddy hasn't been able to get the codes scanned yet (car is still sitting).