12 bolt/8.5'' diff in G Body

[Guest]

I've got a performance buick 350 and a TH400 in my 79 regal. I need more strength in the rear end. Is it possible (and if so how) to put a 12 bolt or 8.5'' rear end in a G body chassis?

[NTX5467]

I believe the 8.5" ring gear rear axle was part of the GNX package and might have existed under a limited number of other A/G bodies over the years.

The 7.5" axle is used in a whole lot of 78-87 A/G vehicles and S-trucks. Interestingly, in the later model S-10 pickups and small Blazers, if you ordered a 4.3L V-6 with a 5-speed manual trans, you got the 8.5" ring gear 10-bolt rear axle. Many of the S-Blazers had rear disc brakes too regardless of which axle was under them. I'm not sure how the spring mounts and widths might compare to your application, but the S-Blazer 10-bolt might provide the core from which to build what you perceive you need. Might also be some Ford 9" rear axle possibilities too.

Some of the performance guys/racers (including our Moderator) might have some more information for you.

Enjoy!

NTX5467

[Jyrki]

I know that the 84-87 T-Types came with a 8.5" axle with 3.42 gears and posi, and that's a direct swap into any 78-87 G-body.

However that S-10 thing I know nothing about.

Jyrki

[NTX5467]

I mentioned the S-10 deal as that would generate rear disc brakes for an 8.5" rear axle that would go in the same place as a 7.5" rear axle. Similarly, the rear disc brakes on the ImpalaSS/Caprice cars are bolt-on situations for other 8.5" rear axles unlike the earlier rear disc brakes on the '79-'81 Firebirds which needed a special rear axle (with cast in caliper mounts) for the rear disc brake setup. In this case, all of these comments would apply specifically to Chevrolet rear axles.

NTX5467