8.5 Rear Identification

[WH1 85]

A friend of mine is thinking of buying what is supposed to be an 8.5" rear with posi. Complete drum to drum. It is also supposed to have stock 3.73 gears.

As far as I can tell this must have come from an 442 olds, right?

Also how do you make sure that it is an 8.5 rear? Checking the gear ratio and the posi should be easy enough. Just want to make sure that it is really an 8.5.

 

[1ARUNEM]

The 8.5 has a more circular cover than a 7.5. The 7.5 is somewhat squared off across the bottom.
An identifying characteristic of the 8.5 is also that it has large "ears" on each bottom corner... The 7.5 has small "ears" if any.. Check www.gnttype.org i think they have a writeup on distinguishing between the two..

Good luck...

 

[NastyGn]

I think you want to look at the casting of the pumpkin under the cover. The 8.5 pumpkin below the rear cover is more square than round, it looks like it has ears on the bottom. The 7.5 's casting is round. Like was said check the tech area of gnttype.org site.

Good Luck

 

[WH1 85]

Thanks for the replies nastygn and 1arunem. We went out today and picked it up. It was a 10 bolt 8.5 rear. Took the cover off and it was a posi. But it did not have 3.73's it had 2.92's.

Guy says it was out of an 84 cutlass diesel. Guess that helps explain the crappy gears. Seeing how diesels are very low revers.

But for an 8.5 with posi complete drum to drum $150 sounds like a steal to me.

 

[turbofish38]

Wait a minute. Something doesn't sound right here. I've been selling parts for these cars for 24 years and they did not offer a 2.92 8.5 in a G-body. Are you sure this is a G-body(Regal-Cutlass) rear end or is it from a B-body(Delta-Park Ave)? The reason I question this is that you could get a 2.93 8.5 in the big cars but not in the mid size. Even the 7.5 doesn't list that ratio. And the 8.5 only came in the Cutlass 442 and turbo Buicks. Never in a diesel of all cars. If you were to lay the 8.5 from both cars side by side they look so alike that the only way to tell is by measuring the length(about a 4" differnce). I guess someone could have put a 2.93 ratio in there but all that I am saying is this isn't a factory combo. Look on the right side axle tube and scrape the dirt and rust away and you'll see the assembly code stamped into the tube. Get those codes and PM or e-mail me and I can decypher it for you. Thanks Eric Fisher turbofish38@hotmail.com