[JLuger]

Can anyone tell me what diff. this is? GM 67 and up 10 bolt 8.5? Its in a 66 GTO I picked up.
thanks

[Tom Vaught]

That would be my 1st guess, as it is designed for a A-Body vehicle vs a leaf spring car and for sure not a typical Pontiac 10 bolt configuration.

The 8.5 rear axle seems to be a lot better rear axle vs the old 10 bolt Pontiac A-Body parts.

Tom V.

[sdbob]

On front right hand axle tube, viewed from rear,should be a code. Usually 2 letters.

[SRR]

I'm pretty sure that's a 8.2 Chevy "C" clip rear.

[JLuger]

I'll be taking it out in a few days and take a better look for any markings on it.
I didn't see any that matched it online figured somebody would know.

[68lemans462]

looks like an 8.2 to me

[Tom Vaught]

The rear cover does look like a Chevy diff cover.
Without the code though it is a 50/50 on being a 8.2 or 8.5 10 bolt rear
cause I know little about 10 bolt chevy rears.
The only 12 bolt A-Body rear did not last long in my GTO.
Post up the code.

Tom V.

[AG]

I don't think the 8.5" GM came out until 1971.

[Tom Vaught]

I would agree with that but it could be installed in any 1964-1972 A-Body vehicle.

Tom V.

[Gary H]

Looks like 8.2" Chevy to me. The 8.5" GM rear has square lugs at the 5:00 and 7:00 location on the bottom of the housing that run parallel to the ground

[Tom Vaught]

Great, Gary H. I will remember that tip.
Tom V.

[JLuger]

Thanks guys I just couldn’t find that cover online anywhere.

[67drake]

This is a ‘71 Cutlass 8.5 that I own. ID’ed by Jim Mitschke at JD race. Looks close, if not identical.
Another good identifier is to look at u-joint retention. 8.2 usually have u bolts holding them in, the 8.5 have straps.

['ol Pinion head]

-there were a little over ONE MILLION '71-72 8.5 A-body rears installed in 71 & 72 GM divisions cars.
-3 different versions of the 71-72 8.5 A-body rear were built. The differences are due to the center housing design, & whether the housing ends accepted A9 or A10 axle bearings.
- one thing ive noted many times: It's never smart to try & identify a housing by poorly written ID Guides & generalities. How many folks use the term "BOP 8.2"? No such thing, just a long time generalization. From decades of hands on experience, there were Early Buick 8.2's, Early Pontiac 8.2's, LATE Buick 8.2's ('68-70), & LATE Pontiac 8.2's. Bunch of differences over the years.

The above pictured rear is indeed an 8.5 A-body rear. Ive posted a pic of that particular style housing on here before & on BuickV8.com when I used to have time to post on that site. In my housing racks have several of that particular style 8.5 A-body housing (only accepts a round cover). Began building up the '71-72 8.5 A-body rears up in the early 90's, while not as common as the style of 8.5 A-body housing that accepts the scalloped style 8.5 cover, have built up over 3 dozen of the style with the round cover.

[JLuger]

I didn’t notice the difference in the straps there was no driveshaft but it looks like a strap setup not u bolts. I have a 66 10 bolt 3.55 with an Eaton posi
for it but want to run a taller gear a friend has a 66 12 bolt with 3.08’s. I was considering But maybe this will work. I’ll try to get to it tomorrow.

[Tom Vaught]

Originally Posted by JLuger

I didn’t notice the difference in the straps there was no driveshaft but it looks like a strap setup not u bolts. I have a 66 10 bolt 3.55 with an Eaton posi
for it but want to run a taller gear a friend has a 66 12 bolt with 3.08’s. I was considering But maybe this will work. I’ll try to get to it tomorrow.

Neither did I. Just blew past the pictures with that info. My bad.

Thanks OPH for the informative post.

Tom V.

[JLuger]

Well pulled it looks like 2.73's 41/15 on ring gear. Not sure how that went with the M20 2.52 first gear, sounds gd for the interstate though.

['ol Pinion head]

2.73 was most common ratio on that particular 8.5 A-body rear.