Look for the code in the glove box. It would be 2.73s or 3.23s. Those are the two factory ratios autos got. Codes are as follows. GU2 = 2.73s GU5 = 3.23s And of course this will tell you UNLESS they have been changed witch is possible but not likely unless the car seems modded.
2009 G8 GT- Borla