Thread: Comp G Transmission Swap

Hello. Looking for a bit of information that I just can’t quite find. Found almost what I need here but missing just a bit of info.

So have a 2004 supercharged com g with a blow transmission. Also have a 2007 supercharged gt with a blown motor. Original plan was to put the 2007 transmission in the comp g. Found here that it can be done just not exactly sure on all the details. Apparently the wiring might be slightly different and the pcm will need programming or changed? Anybody happen to have the pin out for the transmission that might need to be changed?

Other option I was wondering about is what internal changes would need to be done to the new transmission to make use of the tap shift again?

Or last option is to scrap the comp g and just put the motor in the 2007.

To many options not sure which is the best.

I'm in the same boat as you, just reversed. I picked up a Comp G transmission for $250. It's a spare for now as I know mine is on borrowed time.

I think I can just switch valve bodies and be alright with it but any advice is GREATLY appreciated

Wanna trade?

Been searching as much as I can. Payed for some wiring diagrams and decided to put the non tap shift tranny in my comp g car. My diff is toast and the tranny has had problems for the last 50k. Had to be warmed up or revved up before it’ll go into gear.

From what I can tell the wiring is the exact same except the comp g tap shifter sends a signal to c1 pin 45/remote shift. The 2007 has a pin there in the harness as well just obviously no tap shifter to send a signal. Tranny side looks the exact same aswell.

So I am putting it in and now trying to find out how I get the pcm programmed. I do have the 07 pcm but imagine that can’t just be used as is. The local gmc dealer said they can program pcm’s but will they be able to do what I want? Which what I believe is just a 2004 gtp non comp g tune, or maybe all I need to do is get the diff ratio change to 2.93 and disable the remote shift?? Or will this custom programming need to be done at a tunner shop? Anybody know what’ll happen if I try driving as is with a different gear ratio? Throw a code, limp mode, or actual damage?

Good to see the forum back running. Pretty slow in here. But anyway Got the transmission installed and seems to work alright. Next step I believe I need to get the pcm programmed.

Anybody know what needs to be done? Can the dealer program it for me? I believe I just need a 2004 supercharged program just with out the comp g version. Dealer I called isn’t sure but thinks they just go by the vin and installed what ever that brings up.

Or do I need a tuner to get that done?

Pretty sure I replied to this. But maybe it’s in the 3week delay before it gets listed.

Anyway, I reply again. Lots of good info here but lots of mislead aswell. Does look like a good forum 10 years ago.

Anyway. Put the 07 hd tranny in my 2004 comp g car. Checked over every thing I could. The wiring appears the exact same other then the 04 has paddle shifters. So when in manual mode the pcm is programmed to hold it into gear until it sees a signal. Or I believe if rpm gets to high it’ll shift its self.

Have acouple thousand km on the transmission. It’s working fine. Paddle shifters work. Taking it easy as the tranny isn’t shifting perfect especially at high rpm. Am getting a gear ratio code so need to get it changed. Not having any luck with anyone wanting to do that.

Other then the valve body and something to do with 4gear clutch not sure there any difference. Not even sure what the valve body difference does. Seems the Volvo had it do. Do they have paddle shifters? Or is it just for better performance at high rpm?

Day later still no reply posted. Not sure what’s going on.

Swapped it working good. Just need to get the gear ratio changed in the pcm.