I just bought an 89 IROC-Z. Engine is LB9 with a WC-T5 trans. The car has 4 wheel disk brakes and G92 option but when I checked the rear end it has 10 bolts! Shouldn’t all G92’s have a 9 bolt Borg Warner rear Could it be that the previous owner replaced the 9 bolt BW with a 10 bolt

 

could be the previous owner busted the 9bolt and found a cheapie 10 bolt to replace it.

 

in the pre9 bolt days camaros could be had with disk on a 10 bolt, all were posi as far as i know. 9 bolts came along and no more 10 bolt disk rears.

 

well the next thing to do would be to find out the gear ratio next.

its not the end of the world a 10 bolt is an ok rear end.

 

you will be ok, do not worry, unless yo umanaged to somehow break the 10 bolt gm corp axle, it is 7.5" rear. you wil be fine, just drive the car and enjoy it

 

I broke gear teeth in a factory 10 bolt with a 1985 305 LB9 and a 700R4. Albeit, it had 120K on it before it happened.... I would suggest a stronger posi unit and an aluminum differential cap that has some support for the rear bearings built into it..... That should live behind even a modified (within reason) 305 or a stock 350....

 

Im not sure about the ratio but it’s something like 2.7# when speed is 70 in 4th RPM is on 2600 with a faulty speedo

And btw it’s a posi it burns both wheels in power brakes or when a burn some rubber I get 2 lines.

 

In days of old, when there was a Warner Gear Division of General Motors, the ten-bolt Saginaw axle was all we had in medium and light cars. Most of them didn't have the "C" clips until the late '60s or early '70s, and used the bearing flange to retain the axles as the Borg axles did. Most of them didn't break, either. Unless you're on slicks with traction aid and are doing 3,000 RPM clutch dumps daily, a little judicious driving and regular maintenance and inspection should keep the axle going for a long time.

I might be mistaken, but wasn't 1989 about the time that F-bodies stopped using the Borg axle and went solely to Saginaw/New Process Gear axles? Maybe you have a late '89 that didn't have the 9-bolt as an option. If, or WHEN you open the cover for service (if you have over 15,000 miles) and find a locker instead of cone clutches, don't be too surprised. If that's the case, forget about adding friction modifier for the posi unit - you wouldn;t need it.