does anyone know if I can change out my 4t60e for a 4t65e?

 

what year car and what engine? im guessin you have either the 3.4 DOHC or the 3100 if its the DOHC then if its a 96 then yes you would need a new computer (PCM) and harness and the trany.

if it is a 96+ 3100 then similar to the other PCM harness and trany

if it is pre 96 then it is either obd1.5 or obd1 andyou would have to upgrade not only the computer, but the sensors in the car aswell. not all the sensors but a good bit of them