Thread: 99 Regal GS transmission interchange

Hello all, I have scoured the internet to find a definitive answer to my transmission compatibility question. I came across a post on here where someone put a 2005 comp G tapshift trans into a 99 gtp by simply replacing the ecm with a 03 gtp ecm and reusing the old range switch. Well my trans has 212k on it and it's tired. We have a pick your part here with a couple 06 gtps that I would love to snag the trans from to put in my 99 GS. Has anyone successfully replaced a 98-02 4t65e-hd with one from a 03-06? If so what did it entail? Thanks in advance, Nick.

Check out post #4. http://www.grandprixforums.net/threa...-swap-Question

I definitely appreciate the info for sure Scotty. I have sucessfully converted a 4l60e and 4l80e to operate without issue on a couple 03+ GM trucks but I have been out of the trans rebuilding scene for quite some time now.

I don't mind swapping my valve body and channel plate (if necessary). I would probably need a separator plate if these trannys are as hard on the plates as a 4l60 is. But I don't want to reuse my pump because it has seen better days. I found a reman delco pump for 160 but that's how much the entire trans will cost from the yard. Any idea if the newer pump would work on the older valve body/channel plate?

That post is quite interesting and not one that I noticed in the past.

I have done the valve body and channel plate including seperator swap and it works well. the pump is interchangeable, pump shaft is not though. you'll notice the moment you button it up that the shaft won't spin if you have the wrong one.

Ok that's good news. So I just need to retain the pump shaft and pump from the new unit plus swap over the vb and channel plate and all will be well?

Ugh I just backed out of the driveway, put it into D, and got a free revving motor. It's toast. So it looks like I will be doing the swap this weekend.