I just put a built racing 4L60E in my 96 OBD II Camaro. It will WOT shift at 4500 rpms, half throttle it will shift about 5600, and wont downshift at the right time. it has trouble keeping 3rd gear engaged and it doesn't seem to ever go into 4th. On cold start up 2nd gear seems to free rev till it warms up a bit. Converter never locks up(2800 stall) either. I am wondering if it could be the computer having problems since it tells the transmission when to shift or if maybe some valves in the valvebody could be stuck, or if I am way off base completely. Any help is very appreciated. Thanks.

It also seems to like to idle around 1500 in neutral, 1150 in gear and has thrown no codes.

 

Check your TCC selonoid it controls torque converter lockup. You might have to set you OBDII to match your transmissions shiftpoints.

 

Turns out it was my TPS. It was showing a higher voltage at idle than at WOT.... Replaced that and all is well. Thanks for the suggestion.