Hey guys. New member here first time posting. I have tried to look for an answer but struggling to find a clear 1. Im looking to replace the diff in my 2008 g6et which if i am correct has the m86 diff since its a turbo. While doing so im looking at replacing my diff ring and pinion.
What im wondering is.
Number 1
Being an automatic what diff gear does it have in it already?

Number 2
The most accessible diff gear i can find is a 3.7 or 3.9. Cant find many others and of a good brand (i am putting a truetrac m86 lsd in and i can get ring and pinion supplied with it for a good price). Is this a good all round upgrade? Im looking at probly having a better take off without greatly reducing top speed. Also this is my daily and i understand that my fuel ecconomy will go down but i dont want to be guzzling like a big a** v8.

Number 3
If any1 has any better opinions of what i should do, im all ears. Any advice people who have modded there xr6t auto or g6et auto is greatly appreciated.

Let me know if any more info is needed.

Cheers, Mitch

It will be a 2.92 or something like that. If it's a turbo don't bother changing diff gears. They go better with some load on them and fitting diff gears achieves nothing. It's been tried and from memory actually went slower.

I'm presuming being a 2008 that it has the ZF 6 speed auto? If that's the case, anything more than a 3.23 diff will make first gear absolutely useless. First gear in a ZF is 4.17 (or similar), second is close to the 4 speeds first gear (2.3X).

So overall (first gear) ratio of ZF and 2.73 = 11.38, ZF and 3.23 = 13.46

4 speed first gear of 2.39 with 3.46 (XR ratio) = 8.26, with 3.7 = 8.8, with 4.11 = 9.8 (see the pattern here?)

A 4 speed would need a 4.7 diff to achieve similar (11.233) acceleration to the ZF with standard ratio.

As already stated, turbo models like a bit of load to build boost, a ratio change is a complete waste of time.

ZF and 2.73 @ 5000rpm with 245/40R18 will do 54.0kph
ZF and 3.23 @ 5000rpm with 245/40R18 will do 45.0kph in first
ZF and 3.73 @ 5000rpm with 245/40R18 will do 39.8kph in first

4 speed BTR with 4.11 @ 5000rpm with 245/40R18 will do 62.6kph in first gear

So as you can see, numbers speak for themselves. Stock ZF ratios have more brutal acceleration than a 4 speed running 4.11 gears.

Sorry for the multiple explanations.