1968 camaro stock ls6 zo6 motor and 4l60 with yank 3600 red line clutches and beast sun shell , ssp wiring harness ecm is a blue and red connector, just got the car together and brought to tuner to find out car had no speed signal wire , he moved a few pins and got the signal, now trans will start in 1st for fist time and then shift second then it goes almost into limp mode nothing. then u come to stop and even if you put it into 1st it feels like starting in second or third. No codes tuner thinks clutches or wiring, any help please

should i check pin out in trans harness? please need a starting point