I'm just wondering about the RPO codes, Did G92 mean you MIGHT have the 9 bolt.....thirdgen.org says G92 means 9 bolt, and G80 means 3.23, but how can I have both, 3.23 wasn't an option with the 9 bolt....then another site says that the G92 was the 3.23 gear ratio....something is wrong...I'm almost 100% sure I have a 10 bolt....I did go under, but the rear of my car is so low and I didn't have a jack at the time, so I was counting one side of the cover, then moving over and counting the other side, I couldnt' see, so I was just feeling for bolts, I might have counted a bolt twice. If someone can clear the RPO code up for me it would make it alot easier.

My codes:
G92 : AXLE REAR RATIO, PERFORMANCE
G80 : AXLE POSITRACTION, LIMITED SLIP
GU5 : AXLE REAR, 3.23 RATIO



quote:
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G92 and L98(B2L) cars finally got the Borg-Warner HD 7.75 inch four pinion rear end, produced by GM Holden's Limited of Australia (Firebird WS6 cars went to this unit in 1986). These units can be identified by their 9 bolt (rather than 10) differential cover that has a rubber plug. The Borg-Warner logo is also cast into the bottom of the differential case. This rear axle came with tapered rather than straight roller bearings and a cone-clutch rather than disc-clutch limited slip unit. These units came painted black from the factory while most others were bare metal.

G92 for 1987 required the following options:

5.0 TPI (LB9)
Limited slip differential (G80)
Rear disc brakes (J65)
Engine oil cooler (KC4)

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I have all 4 of the required options for the G92, so either the GU5 is incorrect, and should not be there (3.27 was BW, yet GU5 is 3.23) It would be nice if i had a 9 bolt, I need the extra strength

 

You have a 10 bolt. GU5 is a 10 bolt gear ratio.

 

Thats what I figured, did the BW 9 bolts come with their own special RPO, or do you have to check the cover?

If I wanted to put a 9 bolt from a 3rd gen in my iroc, would it be a straight bolt in...or did GM change the car to accomodate the 9 bolt as opposed to my 10 bolt

 

They interchange with no mods. Brakes may be different but that is all.
9 bolt is the way to go since they are stronger.

 

BW 9-Bolt RPO Codes:
GH3 = 2:77
GW6= 3:27
GM3 = 3:45

All came with G80 Limited Slip.

 

i have rear disc, all 9 bolts had rear disc. so it should be a direct swap then...im gonna try and pick one up....how much they go for, complete used rears....

 

Most rear ends go for between $100-150. Depending on where you are and how scarce they are in your part of the country. If you grab yours from a pick and pull, just be sure to take a listing of RPO codes and take them directly from the car that you grab from. You stand a better chance that way of getting what you want instead of just taking the salespersons word that it is what you want.

 

If you are looking for a BW 9-bolt the cost is about $300/500 +freight, the best year is 1989 if you can find one. Reason the big rear disc brakes (11.655 rotors & PBR alum. calipers and 28 spline axle shafts) and a working parking brake. Question, what is wrong with the 10-bolt 3:23 rear you now have??? Actually that is not a bad setup for a 10-bolt (3:23 & Limited slip and disc's) and a 9-bolt is not going to be a improvement over what you have unless it is a 1989 3:45 one. My opinion and I swapped in a 1989 9-bolt 2:77 to replace a a shot 2:73 and that rear was hard to find.

Note: Only 12,300 & unk number of firebirds produced in 1989 with a 350 & 9-bolt rears and biggest number will be 2:77 ratio. So after 15yrs the number available to you is going to be slim picking. No matter what other opinions may be, because they have not actually done it.

 

I'm putting in a 350 next week, I'm looking at 375HP/400+lbs torque....I want to hook, I don't want the rear to go...12 bolt/9" is too expensive, 9 bolt should be able to handle that power range and be cheaper/easier to do.