# Third Member / Center Section



## TheGoatFather1965 (Jul 30, 2017)

I was cruising in my 65' and i was testing the car from a dig, and with the last attempt i broke the diff - ( did a light inspection still unsure ) the third member's case housing broke, not completely but a small part of it. This was a numbers Matching third member housing. I have the 8.2" 10Bolt BOP with 3.23 gears.

#1: Is it possible / Safe to weld the center section's back? #2: is the 1965 GTO's third member a dropout style or would i have to replace the whole rear end?


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## Pinion head (Jan 3, 2015)

The early Pontiac 8.2 center hsgs are made of gray iron, so are the center hsgs of the early Buick 8.2 center hsgs. Pontiacs design incorporated diagonal converging ribs on each side narrowing towards the pinion area. The early Buick 8.2's only had one rib per side, even weaker. Both gray iron styles of hsgs were known not to provide the pinion support for high torque loads. Hsg damage in the front pinion area manifest itself early on in lower gear ratio (3.55 -4.33) rears that were beat on hard, typically 4spd cars that being launched hard. 

Your center housing will most likely have a casting number beginning with a 97xxxx, would be interesting to know this exact casting number. Unfortunately, even properly welding up a meticulously clean crack in the pinion support area of the housing is not going to solve anything. Have welded on cracked upper control arm perches on nodular 8.2's & it is very tricky. The pinion "nose" area is a much more critical load area. The housing is going to have to be replaced & carrier & ring & pinion properly setup or another rear end substituted. For many years i dealt with weakness of the gray iron 8.2's, blown up ring & pinions from lack of pinion support. Seized sealed axle bearings, chewed up axles, damaged 1/4 panels from archaic sealed axle sealed axle bearing design axles seizing & axles departing vehicles typically during cornering. Have removed axle bearings from literally of hundreds of sealed axle bearing '64-69 8.2 axles, just not a fan of a design of axle bearing designed for narrow tires & minimal side loading. For owners on a tight budget that only concerned about getting a vehicle back on the road, all '70 model bolt-in axles finally received tapered axle bearings, This improvement tied right in with GM equipping their A-body's with wider low profile tires. Much more side loading. On a tight budget, & stuck in the Pontiac 8.2 mindset, one can pick up a '70-72 Pontiac 8.2 10 bolt & just the design improvement of the A9 axle bearings is a vast improvement. 

Not satisfied with the limitations of even the rare nodular iron hsg Pontiac 8.2's, & trying to put near 550 ft lbs of torque to the ground with rears that would hold up week after week on the street and strip, there were 3 of us from the N Texas area who simultaneously stumbled onto building up the 71-72 8.5 A-body rears. This was in the early 90's. As hsg cores were plentiful, all of us were scrambling for posi units & housings. Each were building the housings with merely used 8.5 S spring posi units (which at least 2 of us rebuilt properly shimmed up with new GM clutch packs). In the beginning, all 3 competitors set-up mainly nice used 3.23, 3.42 & 3.73 GM gears, many sourced out of early overdrive application GM 8.5 rears. This began to change at least for me, as so many buyers wanted 3.90's, 4-10's, even 4.56's. At the local strips, club challenge series, etc, the basically stock 8.5 A-body rears proved a very strong GM rear, often much more resilent than 12 bolt rears with oem Eaton posi's Typically, on the track, we found the fresh stock 8.5 clutch type posi A-body rears capable of running down into the high 11 sec quarter mile in 3700 lb A-body's with stock axles. As the 90's rolled on, & combinations got stronger, I began to build more & more with Eaton's (newly introduced at the time) 30 spline 8.5 clutch type posi carriers, as well as custom Moser axles. Built with the new 30 spline carriers & A10 axle bearing Moser axles, axle strength was much higher & the new Eaton carriers proved to be a quality improvement.


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## TheGoatFather1965 (Jul 30, 2017)

Thanks for the very detailed reply , you made it much easier for me. My center section's casting number is 9799822. 

The problem is its a numbers matching diff thats why i thought about the welding part with upgraded internals, but i guess that wont work.

Right now im thinking of getting an alternative rear end with the same casting number or an 8.5" as per your recommendation.


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## Pinion head (Jan 3, 2015)

Out of curiosity, what engine is your '65 GTO, have you owned the car for many years? Am betting your '65 GTO's housing has a 9779822 casting number. I've yet to run across an early Buick 8.2 rear in a '65 LeMans or GTO, but have only torn down & rebuilt prob a dozen '65 8.2's out of 1965 Tempest, LeMans, & GTO's . Its possible a few early Buick 8.2's also made it into late built Fremont built '65 Pontiac A-bodys. The early Buick 8.2' rears were used in nearly all '65 & '66 Olds F-85's & Cutlasses. 1965 &'66 manual trans "anti-spin" 442's typically were built with early Pontiac 8.2 Safe-T-Track rears, as the early Pontiac version proved to hold up better than the early single rib gray iron Buick 8.2 rears. as a GM differential builder, I've always got a chuckle out of the "BOP 8.2" term, as Olds was only a consumer in the early years, & by'68, only Pontiac was still using the Pontiac 8.2 rearend, Olds & Buick had come out with their own strengthened designs.

Spotting a '65 Pontiac 8.2, even a filthy one in a yard pile.... the original housing used in the '65 Pontiac A-body was the first to have the larger diam (many would say normal size) upper control arm bushings. The '65 rear is also one of the narrow ones, you can use the 1 finger versus two finger test between the shock mtg bracket & the the backing plate. Like all different '64-66 8.2 housings, it will have the flat bolt on coil spring mounts. In coring out rears from part cars & yarding, I have typically kept narrow 8.2 Pontiac housings, as well as the slightly wider '66 Pontiac 8.2 housings.mThis has been the case, ESP if the housing was factory posi coded, or just extremely clean/ non rust pitted housings. On '67-69 gray iron Pontiac 8.2 rears, I've typically gutted them for good used axles (a rarity), rear covers, pinion flanges, & 2.93-3.23 gears, then chunked the gray iron housings on my scrap trailer. Have traded off many early 8.2 housings & built a few up wity new carriers, gears,metc. For owners whose desire with their '64 & '65's has been extensive handling mods &/or throwing a ton of torque at the rear tires, have built several narrowed A10 hsg end 8.5 rears, as well as quite a few standard width 8.5 A-body posi rears. The 8.5 Abody rears are 1/2" wider at the axle flange than the narrow 8.2's & the '65-67 12 bolts. Ocasionally, a 1/2" wider on each side creates wide tire fit problems. Many times, it doesnt. Over the years have taken a die grinder & carefully reshaped the square lugs on the bottom cover area of the most common style '71-72 8.5 A-body hsg to make it more closely resemble the shape of the 8.2's. In the early 90's, on our swapper bargain build 8.5 posi rears, we even carefully ground off the casting numbers & large A's that are cast into the center hsg, as many tirekickers @ swappers were trying to figure out what hgs we were building up.


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## TheGoatFather1965 (Jul 30, 2017)

Hello,

Yes my casting number is 9779822 sorry for the typo! I kept my 389 tripower aside and i currently have a bolt on 455 making just under 500hp/torque. 

So your saying i shouldnt buy the 8.2" numbers matching rear end with the same casting number that ive found? Or if i do go ahead and purchase the rear end what can i do for it to handle more abuse and power?

Can you give me your personal recommendations of what i can do now? Id like to keep it numbers matching but withstand a little more power. Should i get another rear end and will the 8.5" 10 bolt , bolt in directly or will it need modifications? 

Thank you for your very detailed replies!


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## Pinion head (Jan 3, 2015)

The problem with the gray iron 8.2 rears is even when it was factory upgraded (equipped with 4 pinion Safe-T-Track carrier, first in intro'ed in '66 low ratio 8.2 Pontiac rears), the problem is the gray iron 8.2 housing allows flex under heavy load as the pinion abruptly trys to rise up in its bore. The pinion & ring gear teeth, then bind up & BOOM, parts break... The gray iron Pontiac 8.2's & even the optionsl 67-71 nodular iron center hsg Pontiac 8.2's just were not designed to take near 500 ft lbs of torque under heavy loading. Sure you can throw $1500 at a gray iron 8.2 "upgrading" it, I've had customers that insisted on me rebuilding these gray iron 8.2 Pontiac rears with new Moser axles, new Auburn carrier, new Richmond gears, a new rear "performance" rear cover. Several have also broke them. The problem is the composition of the gray iron hsg, even with all the expensive internal oarts, it still does not want to defy physics under heavy torque loading. For that reason, much more pinion support, as well as wanting to keep the near stock bolt-in axle rear cover looks, then add the MUCH superior tapered axle bearing deign,, that is why I build the 8.5 Abody rears. 

Some history, can note the improvements in design... With warranty problems that were appearing with gray iron Pontiac 8.2 posi rears, mainly behind 3 spd & 4spd GTO's that were being driven hard, Pontiac introduced the nodular iron 8.2 hsg for the '67 3.55-3.90-4.33 A-body Safe-Track rears. Firebirds got the N housing with 3.36-3.90 Safe-t-track rears. The nodular iron center housing prevented a lot of the pinion up/down movement in the pinion nose, in other words, pinion support was increased. It was a bandaid, however, in the heavier performance A bodys. By 1970, when the 455 was intro'ed in Pontiac GTO's and GrandPrixs, McKinnon built 12 bolts were deemed appropriate to take the higher torque loads. While the McKinnon built 12 bolts had better axles & a bigger ujoint flange (3R), these '70-72 Pontiac 455 application 12 bolts also has a standard Eaton 12 bolt posi carrier with brittle weak spider gears. The weaspider like in 99% of all stock eom Eaton posi 12 bolt rears, was the small brittle spider/side gear combination. One of my own keeper '71 HO cars broke its carrier & lh axle in '77 at the strip causing serious drivers side 1/4 panel damage. Fact is I'd never own that car if the rearend & rear 1/4 hadn't been damaged 

Little more history, Olds & Buick also had their own 500+ ft lbs of torque 455's by the '70 model in their top performance A-body's. Both divisions had abandoned the use of gray iron early Buick 8.2's & gray iron & nodular 8.2 Pontiacs by the '68 model year...just too much torque. Both divisions built their own heavier duty 10 bolts, the '68-70 BUICK 8.25 & the type "O" Olds 8.3" 10 bolt. Both bolt-in axle rears were used by each respective division under their own highest performance 70 models. 500+ foot lbs under both. Well before the '71 model intro, the powers @ GM had Buick & Olds both build the 8.5 A-body rear. There are actually 3 different versions of the '71-72 8.5 A-body housings & axles. One built by Buick, & two versions built by Olds. Contrary to a few naysayers, who know little hands on wise about the strengths of the 8.5 A body rears, Buick & Olds cranked out a little over a million '71 & '72 8.5 A-body rears, they are not extremely rare. Nearly all were peg legs, what ive found rarest are factory posi coded 3.42's under again near 500 ft lb Stage1's & W30 cars. Those are a rare rearend, just due to how originally assembled & code stamped. What the 3 of us stumbled onto in the early 90's, is we could take a normal '71-72 8.5 A body rear, build it up with stock axles. Axles which every bit as HD as the axles in the HD Safe-T-Track 8.2's, and with a nice tight clutch type posi run that 3700-3800lb footbraked auto A body down into the high 11's on slicks. That's the limit with the stock axles. With Moser 28 spline axles, high 10's have been recorded, which to me is pushing it a little. Rebuilt with 30 spline Moser axles, a new 30 spline Eaton carrier, 1/2" axle studs, performance rear cover, have equipped several automatic A-body's that have run into the mid 10's. as well as quite a few modified 4spd-6 speed cars that besides all the torque have been set up for handling & appreciate the availability of the larger diam A10 tapered axle bearing.


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## TheGoatFather1965 (Jul 30, 2017)

Hello pinion head,

Thanks for the history lesson i know now whats good and whats not for my pontiac!

I guess i can just weld this back for the future and when i want to return it back to the original. I posted the damage thats been made, the ring and pinion is shattered inside, my intial plan was to replace all bearings and internals and simply weld back the housing, but i guess its not that simple.

- Attached is my 8.2" 10bolts third member housing (Excuse me for the unclear picture).

So your final suggestion is a 71-72 8.5" 10bolt and beef it up so it can withstand more power?

If so, will they fit directly?

Thank you!


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## Pinion head (Jan 3, 2015)

Goatfather, for the torque level you're dealing with, as well as the increased strength, similar appeareance from the back, tapered axle bearings, & all the affordable posi & gear options, it just makes a lt of sense to go with a '71-72 8.5 A-body rear, & yes, it will will bolt in. In stock width form, it will be 1/2" wider axle flange to axle flange than a '64, '65, or extreme early '66 gray iron 8.2 rear. Have narrowed several 8.5 A-body hsgs, as well as narrowed & converted several for use in '65-67 Novas. To continue to use the bolt-in style coil springs in early A-body's, I carefully trim the fluted flange style spring mount on the later style hsgs, then carefully MIG weld a piece of thin steel plate on top, then clean the beads up & drill a holt in the center to recreate each coil spring perch in the '64-66 style. Takes about 45 minutes. The mtg of the rear will then be the same. A stock early LeMans or GTO driveshaft (or a replacement out of a '68-72 4door Pontiac V8A-body) will measure 60.00" ujoint center to ujoint center. With the pinion area of the 8.5 being larger, the 8.5 pinion flange will extend forward slightly, thus the 60" driveshaft will need to cut down to 59 1/8" center to center. If for chance your '65, has a factory 3 spd manual, I do not have the driveshaft length handy, but it's same deal, stock length driveshaft will need to be shortened 7/8". 

As far as beefing up the 8.5, the stock 8.5 axles & tight 28 spline many times are sufficient. My own experience is the stock 8.5 tapered bearing 28 spline axles will hold up fine under a street driven auto car with 500 ft lbs of torque, even one dipping into the high 11's with slicks. Our budget build 8.5 A-body builds proved it many many times. Sidestepping the clutch on a well setup manual trans A-body that can hook up, and can run that quick, thats where even more of a safety margin is needed. That means a pair of Moser axles, & at that point, in a performance 8.5 street/strip build, it's a point where I'm building with a 30 spline Eaton carrier vs the 28 spline carrier. Hope this helps explain better, realize in prev post I got to rambling on various GM rearends strength. Just hard to explain the increasing amt of torque that these performance vehicle's rears had to deal with, & how each GM division made improvements in order to deal with this serious issue in order to avoid warranty issues.


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## TheGoatFather1965 (Jul 30, 2017)

Sorry for the late reply i travelled and didnt look at the forum much!

Pinion head thank you for the recommendation i guess ill have to start searching for 71' rearends.

Hope they are stronger like you said and i can imagine theyre going to handle more than the 8.2".

Thanks alot for the very detailed replies by the way. If it were an aftermarket instead of the 71' would you recommend strange or moser?

Thanks,


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## PontiacJim (Dec 29, 2012)

If you choose to go aftermarket as I did with my '68 Lemans, I went with the Ford 9". My reason being is that the 9" has been around since 1957, and cars from HP to street rods to drag racers have been using them ever since. Aftermarket parts are plentiful and many build their own housings to your specs.

I chose Quick Performance over Moser, Strange, and others just because they seemed to be less expensive, but in the end, the rear end assembly I pieced together as I wanted it was probably no less expensive than Moser, Strange, or any other.

Quick Performance Ford 9 Inch Rear Ends had the housing which I added a few upgrades looking for a rear end that would handle 600HP without issue - not that I will get that out of my 455, but I wanted a rear end to handle the torque, a shot of nitrous, and wide 12" tires grabbing the pavement. Of course a rear that will handle this kind of HP/torque is useless if the suspension/frame are not beefed up as well - which I have done.

The real beauty of the 9" is that it has the removable center section so if you want to play around with gear ratios, you can actually set-up another center section and swap it out - like a gear for local fun or a set for long trip highway cruising mode.

I have not tried it, but it is under my frame and I did not experience any problems. I opted for the Quick Performance 11" rear drum brake set-up which I felt was more than enough with the front disc brake conversion I have added. Again, I mixed and matched all my center section parts then had a local guy assemble it for me - $125.00 which to me was a deal.

I did encounter a problem using the factory type rear sway bar. It will not fit as the rear center housing is larger than the 10/12 bolt. Companies like Spohn make a rear sway bar that will work - but more expense. Not going original by any means, I created/fabricated my own means to attach the factory sway bar going out the back of the rear axle/frame as some newer trucks use.

I believe the driveshaft will have to be fitted, but the universal joint size is the same on Pontiac & Ford. Not a big deal with me as I'm not going original and expect these things during my build, so you want to inquire as to driveshaft fitment with whatever rear axle you go with. 

So do a little research on prices whether a complete turn-key rear axle assembly that will bolt under your car or if you want to piece meal it like I did. Also, options on the type of posi you can install. Some can be more noisy and harsher in locking up if you go with a "locker" style unit. Piece mealing mine together I went with a Power Trax locker https://www.powertrax.com/product-info/no-slip-traction-system/ 

Again, this was my preference and the 9" will be around for a long time so parts will be available, they hold up, and can be a selling point should you ever want to sell. It is not inexpensive by anymeans, but I felt I only wanted to do this once and wanted it to last my lifetime.

BUT, as Pinion head has stated and made mention of his work and the 8.5 10-bolt, this would probably be the best bang for your buck, most inexpensive route, direct fit, and capable of handling your HP. I have a friend with a BB Nova doing 10 second 1/4 mile times with an 8.5 and he swears by them. Says the ring gear will wear over time, but the rear itself holds up to the abuse.

You can often find these on Craigslist for $100-$250 and then build it up from there.


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## TheGoatFather1965 (Jul 30, 2017)

Pontiac Jim,

I like your recommendations as well because i have thought of the GM 8.5" after pinion heads advice because its an inexpensive route until i get something better in the future. I have searched on franks pontiac parts and other places but couldnt find anything, i have yet to search in craigslist. If they handle the power then i dont mind - actually i wanted to keep it numbers matching but pinion head said that there is no point in welding the third member case/housing cause it will just break again, and if it cant handle the power then might as well get something worth it. But for strange or moser rear ends they go for 3K$ plus without installation and all of that. Id rather spend less than that which is why i would go with the 8.5" if i find one. 

I will start looking for one maybe on the forum or craigslist. I found one but he wouldnt ship its local pickup so thats no use.


Do you know of a place that can maybe build me one and ship it internationally and i will pay for all costs?


Thanks!


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## PontiacJim (Dec 29, 2012)

TheGoatFather1965 said:


> Pontiac Jim,
> 
> I like your recommendations as well because i have thought of the GM 8.5" after pinion heads advice because its an inexpensive route until i get something better in the future. I have searched on franks pontiac parts and other places but couldnt find anything, i have yet to search in craigslist. If they handle the power then i dont mind - actually i wanted to keep it numbers matching but pinion head said that there is no point in welding the third member case/housing cause it will just break again, and if it cant handle the power then might as well get something worth it. But for strange or moser rear ends they go for 3K$ plus without installation and all of that. Id rather spend less than that which is why i would go with the 8.5" if i find one.
> 
> ...



Send a message to *Pinion head* as he does rebuild these and may be able to help personally or get you in touch with one of his contacts who could. :thumbsup:


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## Pinion head (Jan 3, 2015)

Will be back up building rearends sometime this Fall. Have racks & racks of clean 8.5 & 12 bolt housings & a TON of experience building performance GM diffs. It has taken literally months to haul in bulky parts, a few project cars, haven't even hauled in my '71's yet. Lot of time spent modifying & putting up HD pallet racking, making fender wrappers. Am currently working on expanding a platform that will have a grid of dealership shelving up top for small parts, with two cars backed underneath. Am getting closer to bringing work benches in, finishing wiring, getting two work stations completed. Then will be closer to beginning to again taking on r/e builds & restoration work. as Jim referenced, feel free & drop me a PM, can detail all r/e options.


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## TheGoatFather1965 (Jul 30, 2017)

Hey PJim,

Thanks man.

And im going to pm you now @pinionhead so we can figure this thing out lol cause the winter is coming soon and i want to be done by then hopefully lol


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