1970 olds 98 12 bolt diff.

1970 Olds 98
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1970 olds 98 12 bolt diff.

Postby 1970 Olds 98 » Fri Sep 30, 2011 9:51 am

Hi, can anyone shed light on the 12 bolt diff in my 1970 olds 98 ?

It has bolt in axles, unlike GM 12 bolt c-clip style. I'm trying to track down a used posi carrier, ring and pinion gears or internals to convert the diff to posi.
I'm pretty familiar with GM rears but this one has me stumped.

Was this diff used in Buick, Pontiac, Caddy etc as well ?
What is ring gear diameter ?
Anybody out there with info or parts available ?

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monzaz
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Re: 1970 olds 98 12 bolt diff.

Postby monzaz » Sat Oct 01, 2011 10:08 am

Hey 70 olds 98... will try to help-

You have a 12 bolt cover with 12 bolts holding the ring gear...MAking this a TRUE 12 bolt rear.

This rear was used from 1967 -1970 olds full size only and 1971 till the 1975 era under 455 buick, olds and pontiac full size cars and wagons.

The ring gear diameter is 9.3"
There are NO AFTERMARKET parts available for these rears.

posi units will use a 'S' spring and it uses square tab clutches will have 12 ring gear bolt holes and use 7/16" x 20 threads either right hand thread and left hand thread.

Mopst common ratios are 2.41 2.56 2.73... 3.08 and 3.23 3.42 are available optional rears and will be found more in the wagons and in areas of the country where mountains are found for climbing. SAME with the posi units...wagons and in the mountainous regions of the USA -

The Posi units will be in different series to hold different ratios...YOU HAVE TO GET THE CORRECT ONE with the correct gears OR they will NOT set-up correctly.

2.41 2.56 2 series / 2.73 3.08 3 series /3.23 3.42 4 series

Axles are 31 spline bolt in axles -67-68 will have sealed bearings MEANING they do not get oiled from the diff fluid.
1969-1975 are all tapered bearing and oiled from the diff fluid with the seal mounted ON the axle shaft .

We have a posi with 2.73 matched set on the shelf but the price is 500.00 for the posi and the gears.

Jim - J D Race.com
J D Race

1970 Olds 98
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Re: 1970 olds 98 12 bolt diff.

Postby 1970 Olds 98 » Sat Oct 01, 2011 10:31 pm

Hey Jim, thanks for the info, its a real help !! I am familiar with the different "series" carriers 2 series, 3 series, 4 series in my 67 chevelle SS 12 bolt. So i'm not surprised to hear that same is true for this Olds diff.

Glad to hear you have a diff and ring and pinion that needs a home. If you have time please fill me in on what it might take to complete a transaction.

Like everyone else i have wishes but lack deep $$$..

I'll check my ratio, but I know mine is an open diff, no springs between the spiders.

Was this a GM corporate diff ? Eaton, Spicer / Dana, etc ??

Let me know if $500.00 is firm, and thanks again for your time and info !!!

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monzaz
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Re: 1970 olds 98 12 bolt diff.

Postby monzaz » Sun Oct 02, 2011 1:52 pm

pretty firm... This would be a trac lock posi same as the 8.5 corp rear with the 'S' same clutches etc. Just the posi housing case is MUCH larger...

Jim
J D Race

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monzaz
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Re: 1970 olds 98 12 bolt diff.

Postby monzaz » Sun Oct 02, 2011 1:54 pm

pics
Attachments
ebay 025.jpg
12 bolt olds full size posi parts 004.jpg
OLDS 12 BOLT POSI.jpg
OLDS 12 BOLT POSI.jpg (25.88 KiB) Viewed 2956 times
J D Race


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