10 Bolt Pontiac vs 12 Bolt Chevy
 

Ok I have a question, are the backing plates and brake details (springs brake shoes etc.) interchangeable between a 10 bolt Pontiac rear end and a 12 bolt Chevy rear?

Yes, 10-Bolt plates, drums, T- bolts and brake stuff being far superior.

Use the 65-72 Big Car Pontiac Yoke on 12-Bolt for better results.

just curious why would you change the yoke? the reason i ask is i have a 72 catalina.

12-Bolt Yoke is for a U-Joint smaller and weaker than the GTO U joint.

Big Car U-joint and yoke are up to snuff, and fit the GTO Driveshaft.

good to know. im trying to absorb as much info as i can. thanks.

Did they put 12 bolt rearends in 65-72 Big Car Pontiacs?

Not in any US built big Pontiacs.

While the big car '65-70 Pontiac 8 7/8 P series rear & the '71-76 8 7/8 MP series rears are both 12 bolts, neither are a 12 bolt Chevy car diff.

So is HIS correct saying that the yoke off the Pontiac big cars will fit a Chevy 12 bolt car rearend? If so do you have an idea where to get one?

'65-70 P series big Pontiacs took a different pinion flange than comparable '71-76 Big Pontiac's. though they will fit on 12 bolt Chevy pinion (& seal), they are not something I use on 12 bolt builds, by using one, one creates another issue, driveshaft yoke compatibility.

GM oruginally built c-clip 12 bolt rears with 3 different pinion flanges (yokes):
-Most common was the style that accepted the small Chevy ujoint (Spicer1310)
-Next version accepts the larger spicer 1330 ujoint. Have only pulled these from rears original to '70 & 71 12 bolts from higher perf Chevelles & Elco's. They may have been used in '69 as well. The ones I've reinstalled used straps & 7/16 headed bolts.
Both the 1310 & 1330 flanges had small **** towards the outside of the pinion flange to locate the external clip type ujoint caps.
-last is the 12 bolt 3R version. The 3R is very similar dimensionally to the Spicer 1330 version, but a 3R ujoint uses internal clips, so flange is smooth to the end of the bore. The oem 3R pinion flanges for 12 bolts are not that easy to come up with used, & the average knowledge mechanic can easily damage the flange where the u-bolts go through. During 12 bolt builds with factory 3R 12 bolt pinion flanges I always set pinion depth without a crush sleeve & use a common 1310 pinion flange. Once pinion depth & backlash are exactly where I need, I disassemble & carefully reassemble with the 3R pinion flange.

Bruce, I have several '65-70 Pontiac 8 7/8 pinion flanges, back on after 7

Therefore another question. I'm pretty sure that the Chevy bolt 10-bolt center hole is slightly smaller than the BOP center hole and therefore the BOP backing plate bolts on to the Chevy, but the smaller Chevy 10-bolt backing plate won't flush up to the BOP axle housing. So is the 12-bolt center hole a little larger and the same as the BOP?

I have been beating on a T400 yoke out of the Oldsmobile station wagon for a long time now. It must be some sort of malleable iron but it stands up to 1.4 60 foots with T brake.

I've seen some beefy TH400 yokes from Olds, and Caddy. Chevy Truck diddnt leave an impression. Hoop strength on TH400 Yokes are surely stronger than Rear Yokes with straps/bolts.

Ford 8.8 Rear seems to have the absolute best Yoke-.driveshaft yoke strength beacuse it is a pair of round plates bolted together. Large Bolts in shear to take the TQ.

My driveline is 1350 so these thoughts are to help those with such parts at hand.

PM sent

I appreciate the additional info provided but am unsure if my original question was answered.

Are the backing plates and brake details on a Pontiac 10 bolt interchangeable with a 12 bolt Chevy rear? Thanks

Yes, this string has gone off the rails a bit!

If you want a definitive answer then look in a Raybestos parts book and compare part numbers.

Look up a like a 68 A body Pontiac and then a 72 Camaro big block.

Just off the top of my head even though both rears could be had with 9.5” shoes, I do not think the backing plates are the same.

The Pontiac used a bearing retainer flange on the axle shaft & housing.

The Chevy used a "C-Clip" retention method for the Axle Shafts.

Not the same brakes based of that difference, I believe.

Tom V.

To avoid confusion, 1971 and newer big car rear ends were different than 1965-1970, they had C clip axles.

C-clip axle 8.2 Chevy-8.5-12 bolt A-F-X backing plates interchange amongst each other. Only exclusion to that rule would be the rear backing plates on an extremely rare 12 bolt rear out of a '65 L16 Chevelle.

The factory use of spotwelded on flange on c-clip axle backing plates used with 9.5" diam drums came to an end at the end of the '74 models. The extra long parking brake cables on early 2nd Gen F-body backing plates disappeared at the same time.


Slightly larger diamer center hole-- i.e., bolt-in axle 9.5" drum backing plates interchange amongst theirselves. There are several different styles, but as long as the rear's axle carried a sealed bearing rw507 axle bearing or a A9 tapered axle bearing, the center holes will be the same size, & backing plates will interchange.

Oddball 9.5" drum backing plates...
Larger diam axle bearings like those used on '67-68 31 spline axle type "O" rears, & at least two styles of Buick & Olds A-body station wagon rears, all these required specific style backing plates, & on one occasion wider rear brake shoes.

Following is for those interested, but ESP, Serious Restorers.
The factory use of c-clip axle spotwelded on flange type backing plates used with 9.5" diam drums came to an end at end of the '74 GM models. The use of extra long style parking brake cables on F-body backing plates also disappeared at the same time.

Last, the 9.5" style backing plates used on McKinnon built 12 bolt c-clip axle rears (used in certain Buick, Olds, & Pontiac A-body applications) did not have the spotwelded on flange. On several occasions, have spotted incorrect detailed supposedly correct 12 bolts under '70-72 455 GTO's. McKinnon built 12 bolts of this variety also used their own style 12 bolt axles with the center pilot being slightly larger diam than the much more common axle used in typical 12 bolt c-clip rears (Chevrolet uses). While original Chevy usage A-F-X 12 bolts continued to use "smoothy" style drums, the McKinnon built 12 bolts like used in '70-72 455 Pontiac A-body's & GP's used the finned rear brake drum. This finned style brake drum was installed at the McKinnon axle plant & will have a stenciled/painted on two letter rear end ID code towards the center of the drivers side rear brake drum. No two letter code color bands were installed on McKinnon 12 bolt axle tubes like we're installed on early Pontiac 8.2 10 bolt rears.

Not all '71+ Gm big car rears, there is a bolt in axle A10 axle bearing 71 up B series rear.

I appreciate your very detailed history on GM differentials but I am having difficulty sorting through your dissertation to find my answer.

In my car I have a 10 bolt Pontiac rear end from a 65 GTO. I purchased a 12 bolt Chevy rear to handle more torque for my new combo. I would like to use the backing plates, wheel cylinders, brakes and drums from the Pontiac 10 bolt on the Chevy 12 bolt. Will this work? Thanks for your advice.

The backing plates off the original '65 8.2 Pontiac rear will bolt on the 12 bolt chevy rear as the spacing between the bolt holes on each rears axle flange is the same. Same diam & width of brake shoes used on the backing plates. Conversely, to install the 12 bolts backing plates on the GTO's original rear would require a lot of time with a die grinder to the center of each backing plate. Not a big fan of stock 12 bolts as an "upgrade".

Throwing the torque of an upgraded engine to a stock 12 bolt posi rear, it's a good measure to upgrade the pathetic stock axles & the weak 10/18 spider gear/side gear combo in the OEM Eaton posi. Also fit a steel LH bearing cap. Currently have three 12 bolt housings in the racks, with broken LH caps/need to be fitted with steel caps in order to be built up. The lower the gear ratio & the harder these rears were "popped" was reason each rear was heavily damaged. Pulled 4.56 & 4.88 pinions out of each rear. Stock (junk) axles with leaking c-clip elims out of one.

Post 2 nailed your question: use every bit of the 10-Bolt Brake setup onto the 12- Bolt.

Throw the 12- Bolt brake setup in the creek ( or try selling em ).

Thanks for refreshing my memory on the 10 to 12 and 12 to 10 swaps, ol pinion head.

I remembered one being a royal PIA. (12 bolt's backing plates on the GTO's original 10 bolt's rear would require a lot of time with a die grinder to the center of each backing plate.)

Tom V.

Thanks for the simplified answer, it was the answer I was hoping for because the new 12 bolt has no brakes or drums and backing plates are in sad shape. As for the 12 bolt upgrade it has new steel axles installed and a new after market posi unit with new 3.08 gears. I am installing it in my 67 LeMans street machine. I believe the 12 bolt Chevy is a strong unit, certainly strong enough for my needs. Many years ago I found a 12 bolt in a wrecking yard, I pulled the 12 bolt rear out of a 65 or 66 Chevelle that had a small block in it and it was a four door car. I installed Moser axles, c-clip eliminators and a spool with 3.73's and stuck it in my 65 LeMans. Drove it on the street for several years started out a low 12 second street car then it evolved into a low 10 second bracket car. The car has hundreds of 12 second, 11 second and 10 second 1/4 mile passes 60' times 1.39 to 1.45 depending on conditions and still runs strong never even changed the oil been running it since 1995 and still racing it. Did some street racing with the car years ago in California too but just couldn't get it to hook up on the street. The only problem I ever had with that 12 bolt was c-clip eliminators would leak oil until I figured out how to remedy that and they haven't leaked in over 20 years.

Not meaning to hijack this thread, but wondering what size the stock 65 GTO 8.2 uses for the u-joint attachment flange? 1330? 1350? I’m changing my 8.2 to Chevelle 12 bolt and need to buy a pinion yoke. Thank you.

65 GTO uses a 3r u-joint from the factory and most 12 bolts have a 1310 pinion flange. You can save some money and get the conversion u-joint.https://www.amazon.com/Moog-372-Univ.../dp/B009HQJGVW

I was planning to use a 1350 yoke, is there a conversion u-joint for that swap? I have heard that conversion joints are weak. Also read here in another forum that a yoke from a big Pontiac will work with GTO u-joint, but don’t see how it would work on a Chevy 12 bolt. Thanks for responding.

https://www.dennysdriveshaft.com/c14...556_insid.html

Thank you for the link. I saw their conversion joints are grease able, meaning they are hollow. I emailed them to see if they have the non grease able available.

Wonder if that Dana Spicer P/N 5-3205X (Neapco) U-Joint is forged or cast. Doesn't say on their website and they don't answer the phone anyone know? I have the same concern not too happy about using a U-joint drilled for grease fitting. Wonder if anyone has a non-greaseable 1350 to GM 3R U-joint.

I tried a quick internet search and could not find any.

Bob

Denny's Driveshaft's website says they have them in stock

https://www.dennysdriveshaft.com/c14...556_insid.html

Fact: i have removed a 65-70s Big Car rear's Yoke and slide it onto a Chevy 12-Bolt pinion shaft input, finished the install and drove without failure nor leak. Did it again on every 12-Bolt thereafter. Go forth and enjoy.

Generally you could say Chevelles dropped driveshafts and GTOs chunked their differentials. But i happen to observe 2 GTOs drop their driveshafts at the rear yoke. I've been at the 1350 U-joint system since. And rims attached with Half-Inch Studs

Ueless Side note: The chevy Kingswood Estate Wagon 12-Bolt Posi rear is of amazing strength and parts sizes, and would come close to Dana60 dimensions. But i never got the Yoke.

You're asking the wrong question.

Why would you use brakes from a '65 GTO (9.5" diameter) when you could inexpensively upgrade to ~11" brakes from a B-body? Enormously more stopping power, dirt cheap at the Treasure Yard. One-tenth the hassle of a rear disc "upgrade" that probably isn't an "upgrade" at all.

Solid 1350 x 3R conversions? Thanks.

I looked again at Denny’s and don’t see any solid non grease able 3R to 1350 conversion u-joints.

I appreciate the info. I was not aware of that possible upgrade. What year B-bodies would have these brakes? So I would need the backing plates, drums, the shoes and all the goodies? You know it's getting pretty hard to find any of these older vehicles at the salvage yards these days almost all of them have been scrapped long ago.

Might be a dumb question but what model vehicles are the B-bodies? Thanks

Chevy B-body would be Biscayne, Bel Air, Impala, Caprice. I'd expect anything from '65--70 would work, perhaps older or newer. That's what I'd be looking for in the Treasure Yard, since you have a Chevy axle.

I'm thinking all full-size Pontiacs are B-bodies.

Olds had a mix of B and C bodies, as did Buick. But C-body brakes might work for this swap also.

I don't know how the backing plates from Pontiac, Olds, Buick and potentially Cadillac might bolt up to the Chevy axle. Knowing GM, they're likely a direct swap in the '65--'70 model year range; but I know that GM had lots of axle assemblies. Perhaps not everything interchanges.

For the record, I grabbed an axle from a mid-'70s A-body that had 11" drums with the intention of putting them on my '68 'Camino with a 12-bolt; but never finished that project. I'd expect certain A-body brakes could work for you, too.

Schurkey,
Thank for the info much appreciated, but now the quest to find a B-Body in the salvage yards, like I said now days most of what they have left is late model stuff cars made in the 70's are all mostly crushed a long time ago.

There's lots of those cars around here in the Treasure Yard.

Because I'm cheap, I intended to use everything but the shoes and some springs from my A-body brakes. But all you'd really need are the backing plates from the Yard, you'd be able to buy everything else new--shoes, springs, adjuster pieces, hold-downs, etc.

I'd rather you hear this from an actual expert like Ol' Pinion Head, but...yes. Far as I know, '65--'70 B-body, and '73--'78 A-body, that have 11" rear drum brakes should be adequate donors. There may be other years, other models. The big deal would be the bolt spacing on the backing plate needing to match the backing-plate bolt hole spacing on the axle you intend to actually use.

I found a 65-72 big car Pontiac yoke for sale on ebay, from Frank’s Pontiac Parts. His ad states it has 28 splines, my Chevy 12 bolt has 30, so I don’t think that setup will work.

Isn’t the the pattern of the 4 bolts on the end of the axle tube larger on B body’s than A body’s ?
I believe that A,F,G and X body cars use the small pattern and B,Y and truck use the larger pattern.I think that the 1965 Z-16 Chevelle is the only A body 12 bolt that will take the B body brakes.
Old’s Vista Cruiser’s and the Buick wagons with the glass tops both have larger rear brakes that will bolt right on. I think that the shoes are 2.5” wide compared to the regular 2” shoes.

That's why I was hoping for a confirmation/denial by one of our axle experts.

30-splines sounda like the Axle-Diff side gears. 30-Spline pinion-yoke for real?

I have a rear set of, if I remember correctly, 69 Vista Cruiser drum brakes.
The shoes are 2 1/2". Same as the front. They require the VC backing plates to work.
I ran them on my 68 for a number of years but had issues with the rear brakes locking up before the front drums. During the restoration I toyed with the idea of using them with a front disk setup but decided to keep the original drums with Muscle Car Brake Shoes.

And IIRC the 73-77 A body wagons had 11" brakes along with a select few Monte Carlos. Again, OPH can confirm.

Yes, unless I counted wrong. I also bought a Moser yoke for it with the same spline count.

It appears that no one knows the answer to my original question. I have swapped the backing plates from the 10 bolt Pontiac rear housing and installed them on my 12 bolt rear housing. I will be installing the Pontiac 10 bolt brake details shoes drums etc. onto the Pontiac 10 bolt backing plates that are now on my Chevy 12 bolt housing. So, the answer to my original question is YES. Thanks for everyone's thoughts but it looks like I answered my own question.

On the 12-bolt Yoke deal: There is a Chevy Kingswood 454 "12-Bolt that is an "oversized freak; more like Dana60 proportions with 12-Bolt looks.

65-70 BOP big Car Yoke should/will spline nicely into the stock Chevelle-GTO-formula400 4-speed 12-bolts.