[4zpeed]

Originally Posted by 'ol Pinion head

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.

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

[Greg Reid]

Originally Posted by 4zpeed

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.

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

[Singleton]

“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

[4zpeed]

Originally Posted by Greg Reid

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

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...


Frank

[Half-Inch Stud]

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.

['ol Pinion head]

Originally Posted by 4zpeed

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...


Frank

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.

[4zpeed]

Originally Posted by 'ol Pinion head

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

['ol Pinion head]

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.

[alsalp]

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.

['ol Pinion head]

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.

[alsalp]

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

['ol Pinion head]

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.

['ol Pinion head]

Originally Posted by alsalp

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

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.

[alsalp]

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.

[Half-Inch Stud]

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.

[scott70]

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

[alsalp]

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

['ol Pinion head]

Originally Posted by alsalp

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.

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.

[Cliff R]

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?......

['ol Pinion head]

Originally Posted by Cliff R

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.