The tranny'* busted in my 2000 Buick Regal. It is a comuter/daily driver so I'm not interested in hi-performance for this car. The engine is a series II L36 and the busted tranny is a 4t65e. What I'm wondering is if I can replace the 4t65e with a 4t60-e which I have on hand?

From what I've read replacing the 60e with a 65e is difficult because the pcm and harness of a 60e car does not suppurt the electronic modulator used by a 65e. But, can I put a 60e tranny in a 65e car, modifiy the plug (delete modulator wires) and run a vacume line to the modulator on the 60e?

You would need to tune the pcm with something like a DHP and Tiny Tuner to be able to make the change. Otherwise you'd throw a bunch of codes and the pcm would reek havoc trying to control the wrong transmission.

Overall though...yes it could be done.