Technical Pontiac/Olds Rearend TECH...post it here...

Gonna try to post some pics here for reference and discussion.


Casting date: E 23 7
Casting#:522496
Stamped #8 to denote original gear ratio




29 spline powerlok diff
1/4" ring gear spacer on a 4.56 gearset
Powerlok case stamped with these #'s
on the case half OPPOSITE of the ring
gear half. 10 6 9 C and 22096X


Casting date:A 30 1
Casting #: 535200
Stamped # 0 for gear ratio and is a 3.08
gearset.





And just for grins a M/T magnesium carrier
that sold on Ebay recently for $320 some.


Feel free to point out any mistakes you see. Mainly wanted to show
difference between 2 and 3 rib carriers.

 

A company called Fabcraft (1 800 208 8242) will help you guys in all your needs they are reproducing the side gears, spiders, and clutch drums for the 59-62 posi's also the 3.6, 3.9, 4.3 ratios for the taller series posis so you dont need a spacer. they also have all the bearings and clutches you would need . Yery freindly folks they saved my ass.

 

In reference to Ramblur's post above, with the pic's...

The first pic: This is a '57-8 2-rib case. The photo is slightly distorted, making it look like it's not perfectly round, but it is in fact perfectly round. Do not confuse this with the SLIGHTLY oblong '56-and earlier third members (which also happen to be a little smaller). Those '56-and earlier ones also have two big ribs. Very easy to confuse them if your eye isn't trained well. This one happens to have a Dana Spicer "Powerlok" posi in it, and the 22096X says that it started life as a 31-spline unit. Someone must have swapped the inner side gears and side gear cups to 29 spline as was used in '57-8.

The second pic: This is a three-rib case, as was used in '59-62 and in '63-4 (the difference there being in the O.D. of the pinion bearing and seal).

The third pic: This is a "Thompson" (Mickey Thompson) magnesium third member. With the two ribs on the side, this particular one is for pre-'57, either a '39-53 or a '54-6. This one shown is not for '57-64, as those had three ribs on the side like what was in photo #2. At least the few that I have seen. The '57-64 rears were commonly used in gassers, and the lighter, smaller pre-'57 ones were commonly used in dragsters.

 

Blownolds, Thanks for your reply and schooling on the Olds/Pontiac axles.
I'll try and edit my post to reflect the correct "Powerlok"name of the posi.
Offhand do you know the gear ratio break for the "Powerlock"that requires
the 1/4" ring gear spacer? I had NO idea that the M/T magnesium piece on
ebay was a pre 57 unit. It just said it was from the 60's and for an"early"
Olds/Pontiac rearend and that they were used in the dragster rails of that time.

 

Yes, the 54?-55-56 ran 16 spline axles, the center carrier/pig is slightly oblong like a 55-64 Chevy, but I have never tried to put one in a Chevy housing. I may have to try that tomorrow.
They can use nearly all the same internals as the earlier rears such as gears, and most bearings. The backing plates should fit all years as long as you have corresponding drums for the plates.
As far as setting back lash, I have always set them up between .005"-.008" trying to stay closer to .005". This is for nearly all the rears/diffs I have done. Some of the new cars are different though.
I get most of my parts from my local NAPA store for rebuilds although I do also use Gevo's Rears n Gears in NY state for some hard to find parts like posi stuff. He always has treated me very well and is extremely knowledgeable.

 

There are three different ratio's of carriers for the '57-64 rears:

1) 2.56 (only)
2) 2.69-3.23
3) 3.42 and steeper

The 1/4" ring spacer is used when installing 3.42 and steeper gears on a 2.69-3.23 carrier.

 

Don't waste your time, it's not even close.

 

This all good information. I have a 56 Pontiac and am looking to upgrade to a Posi. So from what I have read here an other places I would have to probably get my hands on a 57 rear end and a later year 3rd member to bolt into it?

 

You'll also need axles made for that combination, but otherwise essentially yes -

 

That would be your best bet--

Although, "anything" is "possible". I know a guy that says he machined some modifications to a Mopar 8-3/4 posi and installed it into his '50 Olds rearend housing. I do NOT know if he installed Mopar gears along with that, or what.

But if a '57 Poncho rear is the same length as a '56 Poncho, and with the perches in the same place, then that would be a good way to go. Then install a posi third member of your choice (29-spline Powerlok, 31-spline Powerlok, or 31-spline Eaton) along with the ratio of your choice, and then get the axles to fit the setup.

 

I'm selling a rear out of my '53 and didn't realize the gear ratio is marked on the case, what am I looking for and how do I interpret the info?

here's the auction if anyone is interested.

http://cgi.ebay.com/ebaymotors/ws/e...e=ADME:B:AAQ:US:1&viewitem=&item=160137986739

thanks

 

The late build 56 Pontiacs were also available with this rearend. Along with the dual quad 285hp Nascar engine.
47-56 10 spline axle Pontiac rear ends are not available with a limited slip.

 

Will Either a 1957 or 1958 Pontiac Posi fit into a 1957 Chevrolet housing?

Thank you.

 

Did you know that a 57 Odls rearend will run for a couple hundred miles without gear lube... I'm just saying that's all.

 

First off, Pontiac only made posi's for '58 that will fit the '57...and none of the Pontiac parts swap into Chevy rears...those '58 Poncho posi carriers should bring enough money to buy the Chevy parts you need...

 

Understood.

I got the info from a previous post on this thread.

*****************************************************


'57 Pontiac third member will bolt into '57 Chevy housing (checking to confirm axle choices for swap)

'59-'64 Pontiac third member will bolt into a '57-'58 housing with modification and custom axles (custom length 31 spline axles

***************************************************

A 1957 Pontiac third member will fit into a 1957 chevy housing yes or no?

Pontiac never offered a Posi for model year 1957?

I have a 1957 Chevy housing and have a chance to buy a 1958 Posi center section and thus wondering if the 1958 Pontiac posi will fit into a 1957 chevy housing.

 

I don't see how it's possible, '57 chevy rears are smaller than pontiacs...I have both on hand, I'll take some measurements and get back to ya...

 

Anyone else have a definite answer? I don't...as far as I know it won't fit...

 

OK, Ive got t 56 Pontiac 860 2 door Wagon, the Center Section has a Casting of K235. Im guessing this is the Early 56 Rear, 10 Spline. I have not taken it apart yet as the car still moves. The Pinion Bearing is out, and the Gear Set is Howling at Cost or in R. I pulled a rear from a 56 Safari Last summer, but it unfortunatly sat in a low spot too long & was full of water. It IS 10 Spline. So far I have access to 4 or 5 Olds Rearends, but they all have that goofy yoke. Anyone know if I can just Change the yoke from my 56? Ring and Pinion in the Olds & Pontiac the same?

Thanks
Ed Evans
56 Pontiac 860 2 Door Wagon

 

I know the '59-'64 pumpkin won't fit into my Chevy housing...and if a '59-'64 fits in a '57 pontiac, then that means the '57-'58 pontiac pumpkin is too big to fit a chevy...maybe the ring carrier fits, but I doubt that...

 

deffinitly going to use this info, my dad has a 36 roadster with a 57' olds rear under it. Who is the best supplier for re-build kits and ring gears?

 

Napa has all or at least most of the bearings, seals and gaskets...gears, I don't know...try fabcraft...

 

I also have a '64 GP (since '86)- LSD was optional. Only code for it (other than on paperwork) would be a Saf-T-Track metal tag on one of the carrier bolts (in '63-64 at least, PMD put these at the 9 o'clock bolt). PMD also color-daubed one axle end, tho these must all be gone by now on unrestored cars.

'64 ratios:
2.56 (3)
2.69 (2)
2.87 (7)
3.08 (0)
3.23 (9)
3.42 (8)
3.64 (6)
3.90 (4)
4.10
4.30
4.55

'63 PMD shop manual shows axle codes were stamped in the boss next to the carrier bolt @ 8 o'clock (code numbers follow the ratios above). Code numbers are the same for open & LSD rears, but in addition to the different color codes, LSDs also get a green daub- I assume this refers to the axle ends again.

 

Hello:

I have the chance to purchase the following Pontiac Posis locally hence no shipping:

1958 Posi 29 spline

1963 Posi 31 spline.

The taget car will be a 1957 Chevy Gasser.

Is it generally best to go for 31 spine?

Can the axles of 31 spine be cut to fit or must they be replaced?

Thank you kindly.

 

Cut to fit what? Are you still trying to fit a Pontiac pumpkin in a Chevy housing? Why not just pic up a '59-'64 Pontiac rearend and use the '63 posi carrier and swap that into the car...

 

Both of these are for entire 58 and 63 Poncho rear ends meaning center sections with housings with axles.

 

So what would you need to cut the axles for if you get the complete rearend? Yes, 31 spline is better, but if the gearing in the '58 is better or the '63 is too wide to fit the car then get the '58, if the gearing is the same and the '63 fits the car width wise, get the '63...

 

The seller is checking Posi ratios. Will re-post as soon as I have more info.

 

I would pick them both up if the price was right. Didn't need much gear with a 3:97 first gear in a hydromatic.

 

The resale on both rears is pretty good...depending on gear ratio those posi rears can bring in 400 bucks or more...