I have a lt1 and just wired in a 4l60e. its a 12 pin not a 13 pin connection. when i go to drive the car the transmission won't shift out of 1st gear automatically until about 6k rpms. If i shift it manually from 1st to 2nd it shifts but then it tries to shift into 3rd but it just slips. If I allow it to shift automatically out of 1st it shifts fine into all the other gears after that, no slipping in 3rd, but it wont downshift. i can manually make it downshift but it wont go back to 1st gear. starts me off in 2nd gear, no 1st. if i shut the car off and restart it i have first gear again. i dont know what the computer came from originally and need help figuring that out, i cant find anyone with the broad casting codes, without knowing what the computer is from i dont know if this is the right transmission for my lt1. please help

 

It sounds like it has no power. It's in limp mode.

 

do you mean the transmission has no power from battery?