Comp G trans swap Question

**dbcruzr** · 11-03-2013

I have an 01 GTP and I'm about to pick up an L32 with 73000 miles on it that I am going to a mild build for it over the winter. The guy also has the transmission available. Its out of a Comp G with the tap shift. would this trans work in my car without any issues? I know the valve bodies for the tap shift are different, would this cause any issues? I really just would like to get it for the 3.29 gears and then build it from there. Thanks

**Fivefingerdeathpunch** · 11-03-2013

Good luck even trying to make a comp g tap shift trans work in a pre 2004 car.

**OH4CompG** · 11-03-2013

The only way it would work would be if you pulled the valve body and channel plate and swapped them from your trans. You would have to do that to swap chains anyway. Then you need tuning for the new gear ratio

**Shmoke** · 11-04-2013

I had the same question this spring when I swapped a 2005 Tap-Shift tranny into my 1999 GTP. As stated earlier, there are differences but it can work. Being 2003+ the transmission has a different electrical connection scheme at the harness plug. It also has a different pressure control solenoid and a very abbreviated manifold pressure switch assembly, compared to earlier model years.

I found that there is more than one way to skin this cat: Change the harness wiring scheme and iron out the wrinkles with your current PCM or Simply run a PCM from a 2003 GTP (GM P/N 12209624) and leave everything else alone. I chose the second option because it would address both the control signal differences with the new style PCS valve and the wiring changes with one swap. Plus everything was plug-and-play. Just put the existing range selector switch onto the new trans and plug in the 2003 GTP PCM.

The valve body differences between standard and Tap-Shift don't amount to much, P-R-N-D ranges are entirely identical between the two. I worried that selecting the 3-2-1 manual ranges would cause problems but everything works just like normal. Those manual ranges have a few circuit differences that seem to tailor the Tap-Shift trans for faster hydraulic actions during manual shifts but still perform normally without Tap Shift control.

Mine is a Tap-Shift trans but still has the 2.93:1 final drive, so I needed zero trans parameter changes to have a fully-functioning 2005 Tap-Shift trans running in a 1999 GTP using the 2003 GTP PCM. The trans adjustments that I have made are for driveablity with my cam.

Yours would require some custom program work in the PCM to accommodate the 3.29:1 final drive. But that's pretty easy if you know what to change.

P.S. That same 2003 PCM is also working very well on my 2007 L32 engine with the mods listed below and some custom tuning. It was $25 shipped on ebay and included the factory plugs that I need to build an outboard flash setup.

**dsmuts** · 11-04-2013

I'd take that trans off your hands

**dbcruzr** · 11-04-2013

Originally Posted by Shmoke

I had the same question this spring when I swapped a 2005 Tap-Shift tranny into my 1999 GTP. As stated earlier, there are differences but it can work. Being 2003+ the transmission has a different electrical connection scheme at the harness plug. It also has a different pressure control solenoid and a very abbreviated manifold pressure switch assembly, compared to earlier model years.

I found that there is more than one way to skin this cat: Change the harness wiring scheme and iron out the wrinkles with your current PCM or Simply run a PCM from a 2003 GTP (GM P/N 12209624) and leave everything else alone. I chose the second option because it would address both the control signal differences with the new style PCS valve and the wiring changes with one swap. Plus everything was plug-and-play. Just put the existing range selector switch onto the new trans and plug in the 2003 GTP PCM.

The valve body differences between standard and Tap-Shift don't amount to much, P-R-N-D ranges are entirely identical between the two. I worried that selecting the 3-2-1 manual ranges would cause problems but everything works just like normal. Those manual ranges have a few circuit differences that seem to tailor the Tap-Shift trans for faster hydraulic actions during manual shifts but still perform normally without Tap Shift control.

Mine is a Tap-Shift trans but still has the 2.93:1 final drive, so I needed zero trans parameter changes to have a fully-functioning 2005 Tap-Shift trans running in a 1999 GTP using the 2003 GTP PCM. The trans adjustments that I have made are for driveablity with my cam.

Yours would require some custom program work in the PCM to accommodate the 3.29:1 final drive. But that's pretty easy if you know what to change.

P.S. That same 2003 PCM is also working very well on my 2007 L32 engine with the mods listed below and some custom tuning. It was $25 shipped on ebay and included the factory plugs that I need to build an outboard flash setup.

Thanks Shmoke! Thats exactly the information I was looking for! So basically if I get this trans all I need is the 2003 PCM, modify it for 3.29's and Other than that it would be plug and play correct?

**Shmoke** · 11-05-2013

It worked for me. The only problems that I might not be able to forecast would be differences between your 2001 and my 1999.

The only snag that I had was my 1999 cooler lines couldn't be connected on the trans end. I had to buy new cooler lines for the 2000-2003 GTP: AC Delco P/N 10330105 & 10330106. But you've got that covered.

The biggest surprise came during the test drive when I discovered that all of the manual ranges were fully functional. I wasn't expecting that.

And what ever you do - Do NOT forget to connect the pig-tail to the REAR Knock Sensor before you connect the motor to the trans!

Hit me up if you run into a snag.