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.