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Can i use a series 3800 series 3 transmission with a series 2 engine? I was told it got the same bolt pattern and its possible. But got to swap some parts off the old to the new one. Anyone ver did it?

I have. In a nutshell....not possible.

Give me a few moments to say why...check back shortly.

Ok...yes, the bellhousing bolts up just fine. Physically, it' the same transmission (unless we are talking about your '96, in which case, it isn't). MOST Series II 4T65s have reinforced webbing cast into the cases where the bolt bosses are. This allowed the transmission to be placed in different body configurations. Series III 4T65s are fundamentally different in internal wiring and solenoid values. They also have some of those bosses I mentioned done away with or slightly relocated (mainly to streamline them for W-body applications). The needed bosses for a full H-body transplant are not there (What is missing is the rear trans mount. Bosses are there, but are not tapped, and aren't webbed for rigidity).

I used a Series III trans in my '97 buildup. I learned the hard way on what works and what doesn't, and I eventually had to devise a sidepan mount to make it work. If I have to do it all over again, I'd stuff all the Series III guts in the Series II case (and given the direction my '97 is going, that might be sooner than later).

But for a direct swap? NOPE.

Thanks let me know

Check it. Edited first comment.

Being the topic author has a 4T60E and not a 4T65E, the swap would be extensive, including PCM swap and programming, as well as a wiring harness swap.

why do you ask the same quetions in different threads its quite annoying


anything is possible but not worth the work a seris 1 2 or 3 engine and trans are not inter change able plain and simple

a series 1 engine will only fit a series 1 trans series 2 will only fit series 2 and so on and so forth stop asking

This thread is no longer of any use and full of misinformation. Someone PLEASE lock.

Particularly in light of the fact that he's been banned.

3 different times. (and for the record, swiles, you're actually wrong, they will interchange as long as you program the PCM for the correct combination).