I'm attempting to piece together information for my newly aquired 5.7 IROC with it's Factory 9 bolt/2.77 gears. Are there actual differences between the way the disc brakes set up on this VS the 10 bolt? Will I even need to upgrade to an 89+ rear system after all??
Why would someone choose this setup. First: does this have a different rear disc brake system that will interfear with installing the 89 bigger brakes vs the disc braked typical 10 bolt unit? What about routing the rear lines?

Second: I see many posts with people really happy with their 3.*# gears, but little mention of the 2.77. Did it have a specific marketing attraction for GM? What is it best suited for. Any reason not to keep it????

Third: what was the estimated fuel mileage in this setup compared to a H.O. 305 stick shift???

Fourth: Does the normal 3 link system work and all the other suspension parts?

Thanks on this one. There's a lot of posts out there that hint at things but none popping up with detailed information. I'm looking for the details so I can get all the parts ready to go before taking even a wheel off to inspect......
Nitro

 

Where PBR brakes are concerned, the only difference between the 9- and 10- bolt is the backing plates. All else is exactly the same. The following link will provide all the info you require:

https://www.thirdgen.org/techbb2/sho...hreadid=246768

Sorry, I see that you've already been given the link.

JamesC

 

Yes, I got that link, but it's not clear enough for me yet. So I was hoping for more clarification-
Thanks though.
Nitro

 

Strip the old rear end of its calipers, discs, and backing plates. Stick on the new backing plates, new discs, new calipers. Buy new lines. In other words, unbolt the old and bolt up the new. In the above link, I converted a 10-bolt to the bigger brakes. A 9-bolt would work exactly the same way, except 9-bolt backing plates would be used.

2.77's are highway gears and will no doubt save you some mileage (the HO cars had 3.73's).

JamesC