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3.29 Question, and i searched a LOT

S

steves86ta

New member
Hi guys, im new to this site and have been doing some serious searching. All night last night and a couple hours today. I just bought a 2008 GXP and i know the trans will go, its not if its when. And when it does go i want to change to 3.29's. Now i know (from reading on here) that i should only need the 35/35 drive/driven gears, and not the actual final drive as thats what i have now. The car will remain stock minus a CAI, shift kit, and an Exhaust. It also will not be beaten on or drag raced but i do live in the mountains and my commute is pretty rigourous so i would like to do the 3.29's to help with that, itll probably help with fuel mileage as well... I really only have a couple of questions before i order anything.

1. Besides the 35/35 drive/driven gears do i need anything else???
2. Will the car be driveable with the stock tune untill i get it dyno tuned, about a week or two weeks after the rebuild. I know not to floor it as im sure the shift points will be crazy, but still driveable??? My tuner is close to 230 miles away.
3. Anything else i should do to the trans while it is being built to help it hold a little more power?

Thank you all for your time
 


Likely the trans will be very unhapy until you tune for the gears. I'd suggest maybe picking up another pcm or send it to your tuner while your trans is being swapped.
 
agreed, your car will be pissed with the gearing change. You need to have the correct gear ratio in the PCM in the car.

Here is also something to consider Double check that your PCM can actually be tuned. There are some 2008 GP's where the PCM is not compatable with tuning.
 
i have emailed the shop i plan on having tune it and they said it was not a problem. Is there a PCM part number i need to look for or anything?
thanks
 
Odd shifting, maybe limp mode with super hard shifts that feel like they are going to split the input shaft in half (not that 2003 knows anything about breaking inputs..lol)
 


Look on your PCM bottom, if it says acdelco you're in some poop, if it says Delphi you're good to go on tuning.

The acdelco ones can't be tuned, and cars that came with ac delco pcms can't switch with the Delphi ones... The Delphi PCM won't even start the ac delco car. Read my posts in the tuning section under the breakthrough in 2006+ tuning threads
 
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