I have a 68 442 convertible with the dreaded "O" axle rear end and 2.56 gears. Can someone tell me how many splines does the pinion have? Thanks!

 

Who told you that the Olds rear was junk? The O axle was used starting in 67 and thru 1970. I have heard nothing negative about them. Your numericly low gear is not good for quick acceleration but good for the highway.

 

From what I have heard and read there are no longer parts available for this rear end. Im thinking of swaping with a 10 bolt gm from a 68 gto.

 

http://ratechmfg.com/toc.htm

Ratech still makes parts, all you need.

 

If you swap it out, get either a 71-2 8.5 ten bolt or a chubby 12 bolt (assuming you want to stay with GM). The early ten bolt Pontiac rears aren't strong. Quick Performance makes bolt in 9" ford rears and they can fix you up with different levels of cost/strength for your present budget. You can upgrade later when you have more money.

If you had the performance version of the O, meaning 3.42 or stiffer, it would be a good starting point. The standard O rears have smaller bearings, etc. and aren't anything special to be pouring money into.

 

You've clearly heard and read incorrectly.

In addition to Ratech, you can also get parts, gears, and posi... er, ANTI-SPIN carriers here:

http://www.drivetrainspecialists.com...-o-oldsmobile/

 

Lame type "O" Don't get your undies in a bunch.

 

Swapping from the O-axle to a 68 GTO 8.2" 10-bolt is going in the wrong direction. "IF" your are going to swap rears,just get an 8.5" 10-bolt from a 71-72 Cutlass/442 or 71-72 Skylark/GS.You will need to shorten your driveshaft for this swap,but the rear itself is a direct bolt-in.All of the mounting points are the same.
Parts for the 12-bolt O-axle can be purchased,but not on the cheap side.Richmond makes 3:42 & 3:90 gearsets for $280.00.Reider Racing was making the posi units,and were bought-out by DTS,& I have gotten a few from them.Those units are about $525.00 once they get to your door.They are a remachined 8.8" Ford unit with clutches.They weld & machine the ring gear flange area,& redrill a new bolt pattern.I've done the same with a few different carriers.All of the bearings are available at your local parts store,or there are kits like the one Ratech has.You will have about $125.00-$150.00 into all of your bearings & seals,including the axle bearings.Your are looking at about $950.00 in all new parts,before installation.If you can set it up yourself,great.If you need someone to do it,then you have to add that to the total cost.You can get a completely rebuilt 71-72 8.5" 10-bolt,with all new parts,ready to run,for $950.00 plus the freight,but you also need to figure-in the coast of shortening the driveshaft.You always need to look at the final cost,to help decide what the best route is for your application.Both of these rears can take plenty of abuse. To answer your original question,the O-axle has a 27-spline pinion.

 

I have a 68 gto 10 bolt 8.2 housing and was thinking of a total rebuild eaton posi,3.55 gears,better aftermarket axles and all new bearings and seals. I drive a 68 442 convertible and just want a posi rear thats stout enough for the ocasional burnout and romping around town. Would this setup be enough?

 

Thanks for the info! I apreciate it!

 

I bought my first 66 W30 in 1973 and in short order blew the spider gears. The first owner of the second 66 W30 I bought told me that one day at the strip he blew the center section at the starting line. The housing split vertically and fell onto the track. I consider the 8.2" ten bolt "for display purposes only."
The Rund car blew the 10 bolt rear multiple times in 1966-67. The original owner told me he broke the rear in the fourth round of C/S eliminator at the NHRA Nationals in 1966 and that cost him the chance at the trophy which the Brainbeau car ended u p getting.

When I see a restored 66 W30 with the "correct" ten bolt, i know it will never be used for the purpose Olds engineers intended.