I don't have my RPO codes anymore and I am trying to figure out what carier and series gears I have so I can upgrade my GTA from 3.23s to 3.73s. Anyone know where to look or have an answer?

Pull the cover, look for the stampings on the edge of the ring gear and end of the pinion gear.

If 3.23, that's 3-series. Assuming someone sometime in the past didn't change from 2.73's with 2-series 3.23 gears.

87 IROC-Z
Formula
Trans Am
GTA A4 L98 V8 9.3:1 5.7 (350) 225@4400 330@2800 TPI ---- ---- 3.27* ----
*Borg-Warner rear axle


looks like u have a 9 bolt.

www.9bolt.com

Is that a good thing or a bad thing?

good i guess, its a real strong rear end.

I looked at 9bolt.com and didn't really see much there as far as information or pricing for gears. How much am I going to have to spend to get a set of 3.73s for this rear end?

A lot. I can't remember where, but I priced out gears for a 9 bolt and it's like $400 for a gearset instead of the $179 for a 10 bolt gearset. And 9 bolt's have weird gear ratio's so you might not see a 3.73 ratio per say, but something close like 3.70 or something.

Thats not what I wanted to hear I guess she isn't going to be getting new gears anytime soon. $400 isn't worth the jump from 3.23 to 3.73

Parts for 9 bolts are more expensive because they arent nearly as common as a 10 bolt. They are quite a bit stronger than the 10 bolt though. Theres a few companies that make gearsets for them and one company makes axles for them. If 3.45s would be good enough for you, than 5 spd cars with G92 came with those so you could find a used set for pretty cheap.