Tell me about 8.5" 10 bolts
 

Recently I swapped the rear end in my 67 Tempest Wagon to get more highway friendly gears. After sourcing a correct 67 vintage 8.2" with a 2.56 Posi, I set to work swapping the rear out.

After pulling the 10 bolt in the car, I decided to swap covers as I wanted the old chrome cover on the replacement rear as well. Only then did I realize I had something different. The bolt holes on the cover didn't line up. As I stared at things for a minute, it finally dawned on me... I had pulled an 8.5" and was installing an 8.2". With my trusty tape measure, I confirmed my suspicion.

This was a pleasant surprise, as you might imagine, and now I have a spare 8.5" with a 3.23 Posi that works well. I have a feeling it will find its way under my 72 LeMans GT pretty soon.

But here's where I get to my question(s)... I had actually pulled this 8.5" from a 71 LeMans about 20+ years ago, and installed it in my wagon about 18 years back. At the time, I didn't know the difference between the two sizes, and simply installed it as a "10 bolt 3.23 Posi." Who knew. :rolleyes:

So tell me... did Pontiac ever put an 8.5" in one of our beloved A-bodies? I have been under the impression these were found only in Buick's or Old's, not Pontiac's. Is this correct? If so, the LeMans I sourced it from back in the 90's had pirated it sometime before that from something else. Interesting! :o

Second, I know the 8.5" is stronger than the 8.2", but compared to a 12 bolt, are we talking about a step in between 'strength wise,' or are we comparable to the 12 bolt? :confused:

Yes, the 8.5 found its way under 1971-72 Pontiac A-bodies.

It can be as strong as a 12-bolt and many drag racers use them. More plentiful and cheaper than a 12-bolt.

I have a 72 323 nodular 8.5 posi rear end from a 72 Lemans in my 68 GTO, which is stronger than the standard 8.5.

Yours could also be the nodular, check the case for a big N on the drivers side, if so you have a nice rear there.


Frank

Have any pics of that particular housing, Frank?
Would like to see pics of the casting number on center housing.

Thanks for the input, Gents. I'm happy to hear these did come in Pontiac A-bodies as well.

I'll take a peek next week to see if I have an "N" casting. I'll report back. :)

I thought the “N” rears were 8.2’s?

I just looked and I don't have any that show the casting numbers, I should have taken a couple.

I'll try to get a few and post them up, any particular reason why OPH, just wondering.


Frank

Frank, I'm one of the 4 originators of the 8.5 A-body rear buildup & swap. Have built up over 330 8.5 A-body rears since the early 90's. Nearly every one of those rears was built off a core housing which came from a single track rear. Have pulled 8.5 A-body housings & core rears in over a dozen states, I still pick one or two up each year.

Beginning in the mid 80's, my main attention Pontiac wise, has been sourcing parts for & restoring higher performance factory '70-72 Pontiac A-bodys, esp '71 & 72 455 HO cars. Have also hauled in three '72 400 3spd & 400 4spd cars, each of which had a factory Safe-T-Track 8.2 rear. That noted, have never ran across a 8.5 A-body rear factory installed in a '71 or '72 Pontiac A-body. I believe what you may remember as an N is actually a raised A. In the early 90's that raised A along with a few casting numbers, on that particular housing, is something I used to hit with the angle grinder. There was a several year run in the early to mid 90's where when I was setting up at swappers with fresh built 8.5 A-body rears, we were not trying to educate our next competitor. That competition came later.

Very interesting OPH. This was my understanding too.

So what exactly did the 8.5's come under? :confused:

Pontiac installed LATE PONTIAC 8.2 10 bolts in nearly all of its 71 & 72 A-body's & GP's.

'70 GP's w 400's & manual transmissions, as well as all '70-72 factory installed 455 Pontiac A-body's & GP's received 12 bolt McKinnon built rears. The McKinnon built rears have numerous detail differences from a "normal 12 bolt" Malibu-Chevelle-Elco rear.

The 8.5 A-body rear was factory installed under '71 & 72 Buick & Oldsmobile A-body's. Have never ran across a factory installation in a 71 or 72 Pontiac A-body & I've been under tons of them. The axles in the 71 & 72 configurations of 8.5 A-body rear are stronger than the garden variety 12 bolt c-clip axle. Original axles of a 12 bolt taper down, then flare up where the splines begin, this is a trouble spot. The 8.5 S spring posi unit & the factory installed Eaton 12 bolt carriers, are both of a 2 pinion design. The small spider gears in the GM installed Eaton 12 bolt carriers are a trouble spot, and at the least need to be replaced as a 4 piece set.

Chevrolet's '69 COPO Chevelle was equipped with what has to be the high water mark in factory 12 bolt A-body rears. Most on this site will most likely never run across one, only a few were built. Special heat treated axles, ring & pinion, as well as a special 4 series carrier with special side gear & spider gears. In my differential building experience, the only factory 12 bolt that had an edge in strength over a blueprinted '71 8.5 A-body rear. Aftermarket axles & 30 spline Eaton (& Eaton clone) posi carriers are available as an upgrade to the 8.5 A-body rear. If inclined to go 30 spline axles, make sure to note whether the housing accepts A9 or A10 axle bearings, there are 3 different center housing/axle tube combinations.

My apologies to Mister Pontiac if I've misled him in any way.

OK OPH, now you've really got me wondering, I'll try to get some pics of the casting numbers as well as the letter on the housing.

Meanwhile here are some pics I took, just wondering if you can tell anything at all from these, I hate giving someone bad information.

I pulled this rear from a 72 Lemans I owned that came factory with a 4spd, and had assumed the rear end was original to the car.

As in many cases, in trying to answer a question, I've come up with a few of my own, I'm always willing to learn and appreciate any help.

http://forums.maxperformanceinc.com/...4&d=1611725983

http://forums.maxperformanceinc.com/...5&d=1611726005

http://forums.maxperformanceinc.com/...6&d=1611726025

http://forums.maxperformanceinc.com/...7&d=1611726058


Frank

From looking at the pics, the rear is a Pontiac 8.2 10 bolt. The shape of the lower webbing of the center housing is the telltale. I can tell the posi carrier is an original carrier. If this rear has 3.23 gears & a N housing, I would ck the dates inscribed on the gears & the factory code stamping on the housing tube. Either one of two things is possible, a set of 3.23 gears have at some time been set up in an original '72 3.55 STT coded rear's original housing. This would require installing a mid ratio 8.2 STT carrier. Either that situation, or 3.23's were factory installed in one of the remaining '70-72 Pontiac 8.2 cast Nodular housings. Have never seen or heard of that before, but with axle production winding down of the '72 style 8.2 Pontiac rears (73's would take a totally different geometry 8.5 A-body rear) there remains a possibility that Pontiac's axle plant built such a deal just to use up an excess N housing. Would be interested in pics of the stamped axle tube among other pertinent pics. Can relay '72 coded N 8.2 Pontiac rears are few & far between.

A few numbers of interest:

-8.2 BOP uses a 1.438" pinion shaft with 27 splines, while the Chev 8.2" is 1.438" with 25 spline. Compare to the 8.5 and 12 bolt which use a 1.625" shaft and 30 splines. I believe this is a big part of increased strength.

-8.5 axles meet the side gears using 28 splines. 12 bolt is 30 spline, but factory axles (as OPH mentions) are tapered and a weak spot.

I looked for quite a while up here for a 71-72 A body 8.5" to build up as I wanted the bolt in axles, but could not find one. Ended up using a 1968 12 bolt housing that was original to a Canadian Buick, fitted with new Eaton posi, upgraded carrier bearing cap and bolts, and Tom's axles.

If I lived closer to OPH I would buy a 71-72 8.5 housing for a future build :).

Great intel here, Gents. I love these "deep dives," especially when I realize how much I don't know! We all continue to learn, and I appreciate all the wisdom on this site. Thanks for all the detailed breakdown(s). I will have a more critical and discerning eye going forward. :)

I'm happy to know I have an 8.5" on the shelf now. Really making the case for sliding it under the GT as she's currently a one-legger. ;)

Was there not a "Corporate" rear 8.5"?
10 bolt with bolt in axels.

Supposed to be stronger yet. It has been awhile since I had all this info in front of me.
If I remember - there was no 3.55 ratio option. 3.42 or 3.73 options.

"Corporate 8.5" is just a later day description for all the 8.5 differential, not nearly as bad as the foolhardy connotation of a "BOP" 8.2 10 bolt.

GM divisions had a lot of autonomy in differential mfg up into the early 70's when more divisions began to share more specific rear ends. It wasn't that way in the '60's, just compare the rear suspension designs & rear ends under each divisions big cars.

The 8.5 rear design was introduced for 71 model GM passenger cars. GM 1/2 ton pickups would have to wait til '77 model year.

1971 GM 8.5 uses:
A-body: Buick & Olds both mfg 8.5 bolt in tapered bearing axle rears for the A-body.
Little over a million were installed in two production years.

B body:
for '71, most GM divisions used a c-clip axle 8.5 B series rear in their base B series models.
LeSabres, Impallas, Catalina's w 400 engines.
Most likely Olds 88's with 350 Olds engines, can't remember stripping a '71 Delta 88 rear.

F-body, c-clip axle, often when equipped with a posi unit, that posi unit was a Warner Motive cone type posi (think a light duty Auburn style carrier).

1972:
first 8.5 X-body was installed.
'71 Novas & Ventura II' s originally had Chevy 8.2 10 bolts

Cadillac did not use an 8.5 rear till the introduction of the Seville in mid 1975.
These were nothing more than a Nova (X body rear). For '77 model year, the Seville gained rear disc brakes w 5 on 5 bolt pattern axles & rotors. The calipers & caliper brackets for '77 & early '78 model Sevilles was one style, late '78 &'79 are another. In the 90's & early 00's I stripped many dozen Sevilles of rear disc pieces as well as stripped down quire a few to bare housings, occasionally with a #9 (high ratio) posi carrier.

Didn´t Buick use an 8.5" Corporate 10-bolt w/tapered wheel bearings for the 1969 Sportwagon?

Kenth, 69 Sportwagon 10 bolt is a '68-70 BUICK 8.2 rear AKA the late LATE Buick 8.2 rear.
Same style of gearsets & carriers in this rear as in '68-70 Buick GS rears
Another reason there is no such thing as the misused & erroneous "BOP 8.2" ridiculousness.

Have parted several '68 GS 400's & rebuilt a few of this style of rear. Buick Sportswagons of the mid to late 60's are tricky as to original wheel bearing usage. In the earlier years they took a wider sealed axle bearing. Clearing out the cobwebs, if remember right, the '69 Buick Sportswagon axle takes an early tapered axle bearing, I'd have look it up, I do remember its not a Set 10. Hope this helps.

Type "O" for Oldsmobile. were 8.5" rears with either 12-or 10- bolt covers. I only ran across 12- Bolt covers. Stronger than 8.2" BOPs up until you reach the axles as they were same same.

I found Type "O" in a few Stick GTOs 1970, but doesn't make it factory issue huh.

Also found Chevy 12-Bolts in 70 GTO, GP and Stick Formula Firebird, which was factory issue.

Type "O" Olds A-body rears were originally installed in '67-70 Olds A-body's. There was a B-body version as well. Many of the A-body style have ended up in Pontiac A & G's over the decades often due them being a direct bolt in, or hey i found a 3.08 or 3.42 ratio, no other reason. Have had dozens of 28 spline Type "O"s, nearly all coming in under partscars.

Physical Attributes:
-12 bolt smooth cover.... the cover bolt pattern is slightly different than 12 bolt Chevy cover.
-Slightly less than a 8.5" diameter ring gear, some call it an 8.4.
-factory Anti-Spin carriers are of the first S spring design with replaceable clutches.
-Most have sealed axle bearing axles. Similar lack of pinion support as earlier gray iron 8.2 rears.

In '67 & 68, a 31 spline axle version of the Type "O" rear was used in 3.42 & 3.91 ratio rears. Even lower ratio gear sets were available over the counter. These Low ratio '67 & 68 Type "O" rears took their own specific housing due to larger diam carrier bearings/mating caps which were required for the larger diam carrier ends & 31 spline axles. Higher ratio gear sets like 3.08's & 3.23's were used in the standard housings which received carriers with sealed axle bearing 28 spline axles. 2.56's wre very common. For the '69 models, the 28 spline axle was used for all ratios of Cutlaas/442 type "O" rears. Have a '68 3.91 Anti-Spin rear, it's the second I've had & both have had bad sealed bearing axles. To order in new axles & axle bearings & wheel studs ones knocking on $500, the replacement parts add up.

For 1970 models, Type "O" rears used a 28 spline Tapered Bearing axle. ThIs was the year the rare & highly collectible aluminum center housing Type "O" rear was offered. The '70 model Type "O"s are prob the best Type "O" reaes to pick up cheap & throw in a low budget '67-70 Olds Cutlass or 442, if one does not care about the rearend having an Anti-Spin (posi) unit. With wider tires & side loading forces being what they are, this last year of Type "O" rear is not going to go through sealed axle bearing axles like its predessors.

OK OPH, I'll try to get all the info your interested in seeing. I can attest that the gear set is indeed 3.23, I recall seeing that but I'll get all the info that's on the ring gear.

I can also attest it is a N housing, I remember seeing a large N on the drivers side of the housing, I assume that's where the A is you mentioned on the 8.5's is right?

I likely wont have any trouble finding info on the housing, can you assist me with where on the tube I can find the factory code stamp? I did look but didn't see it.

I'm in a similar position with you now and very curious to find out exactly what it is I have. I'll get some pics posted up as soon as I can, appreciate the help.


Frank

Should be on the driver side axle tube. It's a faint stamping so you may have to wire brush it.
EDIT- According to John's site, not all years placed the stamping in the same locations..
http://www.wallaceracing.com/axledata2.htm

“A” on a 71-72 8.5. Also note the green arrow, which shows a threaded hole for the brake line attach point, another way to differentiate an 8.2 from a 8.5

Thanks Greg, with the various types not to mention years, I've seen a variety of different locations they can be found.

That's why I thought OPH having extensive knowledge in many of the different rears could narrow my search efforts.

I'm still trying to figure out why 8.5 was stuck in my mind, thinking back I believe 8.2 is on the ring gear... jeez... :noidea:


Frank

My Typo O would go through Driverside axle bearings.
The Tapered Roller bearing version had me over the barrel for housing fit, long ago.

Typo O Posi can cross pollinate with GM 8.5 rear. GM c-clip axle gears needing C-Clips. O not so.

Frank, the rear is def a LATE 8.2 Pontiac 10 bolt.
Regret, I could not get on here quicker, had some time yesterday to post, but was covered up today, & its going to get busier.

For your 72 rear, the stamped assembly date & two letter code, ck on the pass side axle tube on the front side of the tube directly in front of the axle tube vent.

Problem on the Pontiac 8.2 housings is the location of these stamped codes moved every couple years. Before ck'ing a 72 gray iron housing, I cked a '69 N housing & it's stamped codes were indeed on the drivers side about 5 inches outboard of the center housing. Pitched a '69 GP 8.2 earlier this winter & its stamped codes were in similar position, but above the routing of the brake line. Will be ck'ing a '71 coded Pontiac 8.2 housing thats coming out of a partscar chassis mid next week.

Well hopefully busier is good for you OPH, may the gear God's shine upon your endeavours. I'm more than happy just having your ear no matter the time.

Thank you for pinpointing the location, I did look on both tubes but my efforts were mostly on the left tube as I was under the impression that was the location.

I see that you stated, "the rear is def a LATE 8.2 Pontiac 10 bolt", can I inquire how it is you know it's a late 8.2? Do you mean late 72 8.2 or just a late 8.2?

With any luck at all I should be able to gather enough info off this rear so you can decipher exactly what it is I have, after your comments I'm truly puzzled.

I'm thinking by now I shouldn't even be in this thread since I don't have a 8.5 but I guess there's no harm, Mister Pontiac got his question answered.


Thanks,
Frank

Thanks for kind words, no problem on questions, will try & keep it concise.

The term Late Pontiac 8.2 10 bolt denotes:

-Tapered axle bearing Pontiac 8.2 10 bolt housings & axles.
-7/16" LH thread ring gear bolts with corresponding flange holes in matching carrier.

Original usage:
- late '69 model usage in a Firebird
-'70-72 model usage in a Pontiac A/G body

Have been watching for decades for a factory installed tapered bearing Pontiac 8.2 housing & axles in a '69 Pontiac A-body but haven't run across one yet.

On the subject, I found an 8.5 in a 1975 El Camino. Did they come in those originally? I am thinking of putting it in my 68. Will it bolt in? I haven't measured but my research tells me a 68 has a 60" rear track and a 1975 El Camino has a 60.7" rear track. Track is probably not an issue. Like i said, I have not measured.
It has the scalloped cover like my 8.2 , the square bosses on the bottom, the brake hose mounts on the top (not on a bracket on the notched cover). The only numbers I found are on the driver side casting "N L35". The car is up on welded rim blocks in the yard with the tubes obscured so I havent found any stampings.
I don't know the gearing but comparing the axle/pinion turns I thing they are highway gears. Can be had for $150. My 8.2 has 2.78's. i'm thinking I'd rather regear an 8.5.

alsalp, the '73-77 A-body rears will not fit in the '64-72 A-bodys or '69-72 GP's.
The spread on the upper control arm perchs is wider/a larger angle. The '73-77 A-body rear is also nearly an 1" wider drum to drum. Desiring an 8.5 A-body rear to go in your '68, you will need an 8.5 A body rear from '71-72.

Bummer. I guess the 4 link mounting ears are off then. It even has bolt in axles. Is it worth flipping?

Btw, the pics you've put up are of the bolt-in axle variety of '73-77 8.5 A-body rear. The better alternative for a '73-77 use over the c-clip axle 8.5 version.

Personally, I wouldn't give 150 for it as a core. I have several very clean housings in the racks.
Through the 90's I set up a bunch of '73-77 bolt in axle A-body rears for circle track (Factory Stockers) & prob a dozen of that style housing as 3.42 & 3.73 posi rears. Since that time, I try & not take in any work from the '73-77 guys.

How durable is the 8.2 if i wanted beyond 350hp? i have 2.78's and am looking to change to 3.55 or 3.73's. I don't know if it's worth the investment of new carrier and gears. Also the yard rearend has 11" brakes. Are the backing 8.5 plates compatible to 8.2 and worth grabbing or are they readily available new? Also I'm running 14" ralley 2's.

You will want to keep those 2.78:1 running, for best enjoyment on 70 mph highways. Otherwise begging for Overdrive with 3.55+

Some 14" Rally II rims will rub the Disc Caliper. As for 4-Bolt Drum backplate pattern: probably same from 8.2-8.5-Type O-12Bolt.

OPH...you spoke of the 12 bolts that came in the 455 A-bodies. My 70 455 gto still has its original 3.31 posi 12 bolt. What are the differences between that and the chevy 12 bolt? What parts will interchange? Thanks

I have overdrive. 700r4. My brakes are single piston up front. 9.5 drums in the rear. I was wondering if 11" drums will fit in 14" rims

Durabilty wise, the gray iron 8.2' 10 bolts lack pinion support, that is their major weakness. From '64-69, their axles required sealed axle bearings, an archaic design which are prone to seize & chew up the axle. Attempting to "upgrade" the gray iron 8.2 for a performance build, the limitations will appear, esp when throwing a bunch of torque to the rear & one can get the tires to hook up. For anything other than serious restoration/putt-a-round cars, & desiring a strong GM rear alternative, the A-body 8.5 10 bolt is very hard to beat.

11" backing plates off the later 8.5 A-body rears will bolt on to most earlier housing designs if that is your perogative. I occasionally pull that style 11" backing plates when I run across them, mainly to offer them aa an option in builds. My own rear drum car rears, are set-up with stock 9.5 backing plates with MCB brake in the box kits, then able to alternate original 9.5" drums & later alum drums.

OPH, thanks for the history lesson. As many diff's as I've set up thru the years most have been plain old 8.5 "C" clip variety, a few 12 bolts, and a few later 7.5's. There were transitions years between 8.2's and 8.5's but I thought that the 8.5's were pretty much the "standard" by 1973.

You mentioned someplace about 1977 half ton trucks getting 8.5's by 1977. I've seen 12 bolts diffs as late as 1979. Did they overlap for a few years like the 8.2's and 8.5's in the early 1970's?......

Cliff, On the half tons, the base 1/2 tons began receiving the 8.5 10 bolts in '77, while the Big 10 Chevys & Heavy Half GMC's received the 12 bolt truck axle.

My Dad special ordered a '78 short wide Silverado Big10 w the Big 10 pkg. Basically a 5/8 ton. Believe 1980 was the last year for the Big10 pkg.

On the 12 bolt c-clip axles that found their way under the '70-72 455 GTO's & '71-72 455 LeMans, they were all built of the McKinnon plant in Canada. There was also some usage of this style rear in '68 & 69 Olds A-body's & '69-70 Buick Skylarks. These specific 12 bolts had different axles, backing plates, different drums, and a 3R pinion yoke. All different than the common Chevrolet application 12 bolt rear.

The McKinnon cast 12 bolt housing will also not have a date code cast into the lower pass side webbing. Instead, the housing is date coded on the front of the lower "lip" area of the housing, visible from the front of the housing. On many McKinnon 12 bolts this date casting may not even be legible, the casting date is quite small.

McKinnon (GM of Canada division) also built some 12 bolt "Chevelle" rears for Chevy usage, I've ran across several out of '69 & '70 "Chevelles". These will have the Chevy specific ID codes, as well as the standard duty Chevelle ('70 F-body) length axles, smoothie style drums, & the very common style "Chevy" backing plates with the spotwelded flange.

Well. Aren't I embarassed.

I have learned something new, and I wasn't expecting this.

I was sure that the 8.5" wasn't used on B-bodies until the major downsizing in '77, when the B-body was shortened and lightened; basically a boxy body on a modified A-body frame.

And I thought the first use of the 8.5 on pickups was for the '88 model year which started earlier than usual in '87. The 8.5 was upgraded in late '88 for '89 model year with 30-spline axles and side-gears, maybe bigger bearings.

I believed that the 8.5 was a wonderful axle for compact and intermediate cars using small-block engines, but had no business behind a big-block or under a full-size car; and the 8.5 is a hot mess under a full-size pickup. Seen too many 8.5s shattered and exploded under GMT400 trucks. Strangely, I've never seen a blown-up 8.5 under a Squarebody truck.

Abused Eaton Govenor locks have taken out more gearsets & 8.5 rears in pickup housings than anything else. Very rarely have I ran across a blown up 8.5 ring & pinion even in a street strip car build.

What i ran into alot years ago was many young owners thought with a lift & big tires, their "truck" was ready to go to the river. In the course of playing at the river, doing big donuts, etc, the Gov-lock rear was the weak spot. The Gov-locks just do not like two big rear tires/rear of the truck being thrown in an arcing manner.

When a Gov-locks blows & takes out the ring & pinion, they typ take out the drivers side cap, as well as many times taking out the cap mating area of the housing. From there, the owners typical action was a search for another rearend. The chance of finding just a core rear or housing in the cheap yards was usually very slim as the 4WD 8.5 housings & axles are of a different length than the 2WD variety. For a while, I pulled that particular 4WD pickup housing in a few Pick-N-Pulls, eventually rebuilding them with a new clutch type Eaton carrier, or in a few cases with used 30 spline Auburn posi carriers out of B series 8.5's (impallas & Roadmasters).

Is the carrier the same as the chevy 12 bolt? Didnt know if a chevy 3 series posi carrier would fit if anything went wrong with mine.My diff cover looks identical to a chevy 12 bolt cover. Also the rear pinion yoke takes a U bolt and not a strap for the U joint.

the carriers & ring & pinions are the same.

what are the carrier breaks for bop 8.2's?

2.56 and 2.78

2.93, 3.08 and 3.23

3.36 and numerically higher.

"Cliff, On the half tons, the base 1/2 tons began receiving the 8.5 10 bolts in '77, while the Big 10 Chevys & Heavy Half GMC's received the 12 bolt truck axle."

I've seen the 12 bolts as late as 1979 so knew they still offered them in some applications. My 1979 K-5 Blazer had a 12 bolt in it, and it was the only 12 bolt I've ever seen with the Eaton Locking carrier in it.. Those do get a bad rap for blowing up, but I've never had the first issue with one and have owned many GM trucks, Blazers and Suburbans with them. The death sentence for them is putting one wheel on wet grass and the other on pavement and whacking the piss out it. Over zealous youngsters also try to do hard right hard turn burnouts with them at every stop sign they come to and they don't last very long doing that either.

I've found them difficult to rebuild and service, and had to make special tools to press the governor and latch assembly out of them. I still consider them an excellent part for what they were designed for, but a very poor choice for drag racing diffs.......

https://www.youtube.com/watch?v=ftyJvIO0DZ8

[QUOTE=So tell me... did Pontiac ever put an 8.5" in one of our beloved (Pontiac) A-bodies? [/QUOTE]

Short answer ... Nope. BOP 8.2" 10 bolt w. bearing flange axle retainers was specific to Buick, Olds and Pontiac. Chevy had its own 8.2" 10 bolt which utilized C clips for axle retention before the corporate 8.5" 10 bolt became the norm.

Good article here: https://www.hemmings.com/stories/art...o-p-rear-axles

Quite a few errors in that "good" article.

Pontiac most certainly installed 8.5 rears in nearly every '73 A-body.
Mention "nearly every" as there were the 8 7/8 MP series rears that came in the SW's & for a few years in numerous 455 powered GrandAms, etc,