its a iroc-z 88 5.0 tpi automatic with a shift kit installed and uninstalled when the shift kit was first installed when you would hit the gas it feels like a bowling ball in your trunk slamming against the back and ripping the car apart NOW the car wont come out of second. Drives fine but will NOT pass second

 

I had the same sort of problem when I had my 85TA it had a shift kit , the govenor in the trans had a peice of the nylon or plastic cogs broken . Once I replced it trans worked fine , but make sure you use the same counter weights that are in your trans now or it may not shift properly. Mine came out of a v6 trans and it wouldn't shift right , so I just put the original weights on the replacement govenor. This could be one of the problems and is a easy and cheap fix. Good luck