not sure if my car has it. whats the rpo for posi? possible to tell which ring and pinion gears are in car by rpo?

 

G80 = posi

 

The RPO's will tell you the gear ratio also, look for a GUx code. Just from your description (91RS, V8, auto) you've got 2.73's unless the car is a B4C. If it's TBI it's 2.73, end of story. However the best way to know is to pull the cover off the differential, find the stamped numbers and it'll either have the ratio clearly stamped or it'll have xx:xx, in which case divide one number by the other and you'll have the ratio.

 

gu5=3.23

gu6=3.42

g80=positraction-limited slip

 

Unless the rear end has been changed, the only stock gear ratio available for his ride (1991, RS, V-8, Auto tranny) is the RPO GU2 = 2.73
(as mentioned by Drew)

 

If the your Camaro spent her life in Arizona the axle code may still be readable(I'm lucky the codes on my '83 are still very readable).It's stamped into the right axle tube on the pinion side.It will give the axle code(gear ratio)the code if it had positraction and the production date.Again as mentioned if the gears haven't been changed or the entire assembly itself.But it sounds like stock the V8 RS was stuck with one gear option.

 

thanks ill be sure to check there. shes always been in az and cali so its real clean, i should be able to read it

 

You don't have to pull off the cover, just turn the rear wheels and count the number of rotations of the drive shaft to one rotation, the number of the rotations is your gear ratio. Ex. 3.5 rotations = 3.50:1 gear ratio

 

I always thought (incorrectly now I know!) that the Camaro and Firebird used the same axle code RPO's. Turns out my '85 IROC is a GU4 = 3.08 where my '89 TTA is a GW6 = 3.27 .... Learn something new every day it seems!

Mike

 

What's so unusual about that? You've got two different cars with two different differentials with two different gear ratios.

 

I don't think it's unusual at all ... I was just saying that I have always thought they used the same "GU" RPO scheme. Not until I read this thread did I think to look at mine.

 

what do you mean scheme ?

the G letter prefix codes are rear axle and suspension group codes


camaros and birds and other models of cars including trucks did use the same code for a given ratio

and GU is not the only series of g codes
theres GT and GQ and GS and GN and GC and so on

http://www.drivetrain.com/GMtrkratio_posidata.html


im not sure what you mean


good luck

 

Thank you Randy for the link.Good info on that website.

As you stated the "G" prefix in RPOs has always been at least rear axle code related.G80 has been the RPO for positraction/limited slip since the mid '60s if not earlier.My '73 CST has the truck 12 bolt and the RPO for positraction is G80 on her.It's funny they used a version of the SPID back then the stopped then went back to it.

 

Camaro and Firebird do use the same codes. My 87 IROC-Z also has GW6 for 3.27. I think he thought that because the Camaro had a GU code and the Firebird had GW that the manufacturer was using different codes for the different models. I don't know if the coding is different because all GU codes were already in use when the Borg-Warner rear was put in our cars. That might account for the GW labeling.

 

That's good info - I know these cars are different manufacturers, but I'm always interested to know where they are similar and where they are different. Just curiousity ...