[360Rocket]

So I have a 1970 Pontiac GTO with a 12 bolt rear end. I am removing a 4 series carrier and replacing it with a 3 series carrier. Rumor has it the 3 series came out of a 1968 Chevrolet Chevelle. So I'm having to use the Chevy pinion/yoke and of course the Pontiac drive shaft. I am struggling with tracking down an adaptable U-Joint and even more importantly a useable U--Joint part number? I've gone thru a couple of MOOG U-Joints that have just missed the mark, your help would be greatly appreciated. Thanks

[johnta1]

I take it your GTO didn't have a 12 bolt in it originally?

These I think are the U-joints that should work?
(been a very long time since I did this)

Napa PN 372
Precision 372
Neapco 3-3130
Spicer/Dana 5-3022X

I used the 5-3022X I think.



But probably easier to take one in and compare.

[360Rocket]

No I'm pretty sure it did come with a 12 bolt. This was a Canadian built car and from what I can gather these had Chevy 123 bolts installed from the factory?

[360Rocket]

Thank you John, that part number matched all the measurements that I need . Damn that was fast. Thank you again.

[AG]

The Pontiac 3R 12 bolt yoke should work, all 12 bolt pinions had the same spline count regardless of Pontiac/Chevy and U-join difference.

[360Rocket]

For anyone interested the MOOG part number is 372.

[360Rocket]

Originally Posted by AG

The Pontiac 3R 12 bolt yoke should work, all 12 bolt pinions had the same spline count regardless of Pontiac/Chevy and U-join difference.

Not exactly sure why it isn't working but ??? I have no idea, maybe a difference in the carriers? It came originally as a one wheeler 3:08 from the code on the axle tube? Unless I am reading that wrong? So it started as a 3 series carrier from the factory. The axles that came with the carrier ended up being too long as well.

[AG]

Your car only came with a 12 bolt if it is a 455 car. Take pictures of the casting number on the rear and the 3 series carrier, what is the code on the axle tube? The carriers have nothing to do with the pinion yoke.

[sd7369]

Chevy used a smaller u-joint than Pontiac, and even though both are the c-clip rears, yoke is different. As mentioned, carriers have nothing to do with the yoke. You can't mix 10 bolt BOP, 12-bolt Olds or chevy 12-bolt yokes, none will interchange. To use the Pontiac driveshaft you must use the Pontiac 12-bolt yoke which are exceedingly hard to find. There is a u-joint available to mix the chevy yoke with the Pontiac driveshaft. Your pictured code appears to be a chevy c-clip rear code.

[Rocco Testa]

If I remember correctly lakewood was the one I used a long time ago or it might be Moroso. Each joint has a different yoke size. Hope that help you some. If not try posting in the race section someone they may know.

[400 Lemans]

Looks like you have the narrower 12 bolt from 65 to 67 chevelle maybe. 68 to 72 12 bolts are wider so the axles would be longer. Just use your shorter axles. Your carrier will work fine though and you need the 1310 to 3r adapter u-joints from post 2.

[tekuhn]

The 3R (S44) pinion yokes for Chevy 12-bolt are indeed very scarce. I couldn't find a single one, new or used, online. There are 3 common u-joint size pinion yokes readily available for the 12-bolt. 1310, 1330, and 1350. You apparently have the 1310 which is the smallest of the three. Big block Chevy's usually got the 1330 pinion yoke. The 1330 u-joint is very close in size and strength to the 3R (S44) that Pontiac used. If you need to replace your yoke while rebuilding the differential (old one grooved?), you'd might as well upgrade to a 1330 yoke as there's virtually no price difference. The hybrid u-joint you need for that is Spicer 5-793X. 1350 are very commonly used for racing, but would be overkill for street use.

Here's a 1330 yoke that uses U-bolts. There are also versions that use straps and bolts if that's your preference.

https://www.dennysdriveshaft.com/p37...y_12_bolt.html

[00fxd]

If it’s any help, 40ish years ago, I used Borg Warner part# 114-9hd to use a 68 Camaro 12 bolt in my 68 Firebird 4spd.

['ol Pinion head]

The 3R 12 bolt pinion flange really isn't worth chasing, unless you have are involved in a very high point Concours restoration on factory 455 / 455 HO A-body car, and even then, most well versed national show judges wouldnt know the appearance of a factory 12bolt 3R pinion flange from an aftermarket cast steel Spicer 1330 piece. Would agree with tekuhn, the u-bolt style spicer 1330 12 bolt pinion flange is the way to go. Ignore the Parts Place listings & other sellers who are selling a spicer 1330 pinion flange with bolts & straps for the '70-72 455 application 12 bolt, that's incorrect.

Rebuild tips for those with a factory 12bolt with factory installed pinion flange.
During a build with a factory 3R 12 bolt pinion flange, one has to be very very careful reinstalling a factory flange, as if there is any "rock" of the pinion flange holding tool when bolted up (Kent Moore or aftermarket slotted style), one or two of the corners of the 3R 12 bolt flange can chip out, ruining the pinion flange flange. When rebuilding McKinnon 12 bolt rears which came with a 3R pinion flange, I go through the last phases of the build with a common 1310 12 bolt pinion flange. This means using the 1310 pinion flange to compress the new crush sleeve to "near" correct final dimension. Only after the differential has patterned out, do I use the 1310 flange to compress the crush sleeve. Then, I install the correct pinion seal (McKinnon 12 bolt & 3R pinion flange used a different pinion seal), & oh so carefully tighten the factory 3R 12 bolt pinion flange using a pinion flange holding tool of my own design, & the 3/4 sliding breaker bar & 3ft piece of thick wall pipe. Carefully installing this pinion flange in this way will result in no damage to the flange.

[tekuhn]

Originally Posted by 360Rocket

Not exactly sure why it isn't working but ??? I have no idea, maybe a difference in the carriers? It came originally as a one wheeler 3:08 from the code on the axle tube? Unless I am reading that wrong? So it started as a 3 series carrier from the factory. The axles that came with the carrier ended up being too long as well.

I think you might need to do a little detective work here. Reading between the lines of your post, with the 4.XX gears, were you using a standard Pontiac 3R u-joint and not a hybrid? All 12-bolts regardless of gear ratio would accept the same pinion yoke. By that I mean it will physically bolt on, regardless of which u-joint it's sized for. If your 4.XX gear set and your 3.XX gear set are not allowing you to use the same yoke, then there is a problem. Are both pinion gears the same bearing diameter and cut with 30 splines? You mentioned the new 3-series carrier coming with axles that were a different length. It's true that the '64-'67 A-body 12-bolts were about 1 inch narrower than the '68-'72 and had axles that were correspondingly shorter. (BTW, Pontiac went 1 inch wider two years earlier in '66). Again, your original axles should work with either carrier. Are both sets of axles retained by C-clips and with the same diameter and number of splines? Did both ring gears have the same bolt pattern and bolt circle diameter? I believe these should each fit the others carrier, although the thickness would not be correct. The only difference between a 3-series and 4-series carrier would be the ring gear offset to maintain alignment with the different pinion gear head sizes. A 12 tooth pinion head is necessarily larger in diameter than a 9 tooth. At some point you can't maintain proper ring and pinion mesh by varying the ring gear thickness and it's necessary to move the ring gear offset with the carrier.

I guess if you have this gear swap complete and working properly then you're all set, but if this is still in progress, I'd strongly recommend you thoroughly inspect all these parts and make sure you know what you're working with. All part numbers as well as dimensions and spline counts are readily available on the Internet. Start with the part number for your differential housing and take it from there so you know what you've got.

[tailored68.........]

See if you can obtain an earlier Pontiac 10 bolt Keep it pure....