LSfast1

I have a factory rear end in my 99 Trans Am. it is an a4. what rear gears do i have? are they the 2:73's or 3:23's? thanks

josh

2001NBMZ28

Look at the RPO codes on the drivers side door - GU2 2.73, GU5, 3.23

MountainMotor

iTrader: (2)

Just watch your rpm's on the highway. If your running around 1600rpm's at 60 then you have 2.73's, if your running more around 1900rpm's then you have 3.23's.

LSfast1

thanks guys. i couldn't find the rpo codes on the drivers side door. becasue i don't have the factory DS door. it got dmaged in a wreck. so i'll juts look at my rpm's and see. i'm thinking i have 3:23's though. and if i do how much will it help changing to 3:73's? thanks

josh

2001NBMZ28

Good point, double check against a gear/RPM calculator like www.f-body.org/gears/ to be sure. My car says GU2 on the door, but has a "factory" 3.42 rear in it from an M6 car.

MountainMotor

iTrader: (2)

3.73's would help but not near as much as a stall. If you do have 3.23's then I'd definately go for the stall first. I'd actually go for the stall first even if I had 2.73's. The gears will help but not as much as a stall in an auto.

LSfast1

thats what i had planned on doing. but 'm probably gonna be selling my car anyways. but thanks again for the help guys.

josh