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Olds Type "O" Rear posi conversion

Posted: Mon Apr 02, 2012 3:03 pm
by csouth
I've heard this is THE place to come for rear end/differential related questions. I have a 72 Cutlass where the rear end was changed to a type "O" 12bolt cover/10bolt ring. I'm trying to find out what vendors make posi/lsd units for them? I was hoping to find an Eaton unit, but I was only able to finda part number listed for 10bolt cover. Units for these seem to be scarce. Any help offered would be greatly appreciated.

Re: Olds Type "O" Rear posi conversion

Posted: Tue Apr 03, 2012 3:46 pm
by monzaz
Good to here the word is speading ...:)

We build the 12 botl Olds posi units.

we have 28 spline and 31 spline Full spools reconditioned original unit and aftermarket units
Rebuild kits axle bearing kits
Ring and pinions
AND Custom axle shaft and replacement axle shafts NEW and Used

SO... First we need to start with what ratio you have and axle spline the axle has in it?

1967 1968 rears can be 28 or 31 spline
1969 -1970 are only 28 BUT witrh the custom axles we build you are NEVER limited to 28 we make 31 spline axles too.

We also sell true trac posi unit for the olds 12 bolt too.

J D Race
330 990 8155

Re: Olds Type "O" Rear posi conversion

Posted: Tue Apr 03, 2012 11:12 pm
by csouth
I believe I have 28 spline axles.

Re: Olds Type "O" Rear posi conversion

Posted: Wed Apr 04, 2012 7:21 pm
by monzaz
We are in the process of another run of posi units - We were trying toi get them in before the spring rush but seems the machiniest are getting backed up too. I am pushing to get the unit through quicker BUT it is tough to get the fire under the BUTTS...LOL. Jim

I just sold the last 28 spline 2 days ago - Eaton unit. They are just a better unit that the stock ones.

We do have a 3 series reconditioned original that one is 425.00 as we sell them to guys that are restoring cars back to number matching parts. Jim

What ratio were you looking to go to?

Re: Olds Type "O" Rear posi conversion

Posted: Thu Apr 05, 2012 4:18 pm
by csouth
Well My car is far from a numbers matching resto, so aftermarket is good for me. The car will have overdrive, so I'm thinking 3.42? The tire will be @ 27"


Re: Olds Type "O" Rear posi conversion

Posted: Fri Apr 06, 2012 12:57 pm
by monzaz
Sounds pretty good to me tire size etc. What is the ratio right now? Jim

3.42 12 bolt OLDS gears FOR SALE NEW

Posted: Wed Jun 25, 2014 10:54 am
by monzaz
we now have the 12 bolt 'O' type gears in and for sale NOW!

rebuild kits 109.00
posi units from 385.00-495.00 28 spline

a few w-30 HIGH performance 31 spline posi units also.

Thanks, Jim Mitschke