10 bolt/12bolt 8.875 full size

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brian79
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10 bolt/12bolt 8.875 full size

Post by brian79 »

Are there any parts for these rearends. Gears/posi units/spools. A friend of mine hase one just sitting around and was wondering if there are any upgrade parts for it?
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monzaz
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Re: 10 bolt/12bolt 8.875 full size

Post by monzaz »

Unfortunately no aftermarket parts. BUT you still should be able to find them out there. I just found a whole Caddy rear from a 1976 deville with 3.42 and posi...VERY good find as 3.42 was the best gear in the mid to late seventies. The early Pontiac 10 bolt 12 bolt rears had 3.73 in the day...BUT still pretty hard to find since that gear would have been for a performance 2+2 car 421 etc. Jim

WHAT we can do is reengineer a 10 bolt 8.5 to bolt into your older car fairly simply if we have all the perch component and or tubes from your old diff. Jim

If this is something you might be interested in we can talk....


NOW here is another bit of info...Brad down in TEXAS of Fabcraft metalworks is producing gears for these 120 bolt 12 bolt rears and will fit all the 1965-1977 12 bolt full size cars with the 10 bolt covers.
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WMACHINE
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Re: 10 bolt/12bolt 8.875 full size

Post by WMACHINE »

That includes my '65 Olds Jetstar 1 (3.23 posi)?
brian79
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Re: 10 bolt/12bolt 8.875 full size

Post by brian79 »

are these strong rearends? how many splines on the axles? (just for my personal knowledge)If it has 12bolt 8.875 inners why don't the 12 bolt parts work with them?
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monzaz
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Re: 10 bolt/12bolt 8.875 full size

Post by monzaz »

oLDS JETSTAR, Good question ... But yes they are in a league all there own AGAIN! 1965 was a 1 only year in a lot of car diffs. Kind of a transition year. Very tough to get all the correct seals and axle bearing parts a lot of the time. It does appear to have the same bearings as a lot of the larger olds cars. As far as making the parts fit, it could be a possibility to work. I would need the rear in front of me to take the proper measurements. Jim

We have a friend down in Texas that is working on these 10 bolt 12 bolt gears righ tnow and I can ask them about this question. Jim
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monzaz
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Re: 10 bolt/12bolt 8.875 full size

Post by monzaz »

10 bolt 12 bolt rears strength:
They are strong as they were full size car diff and had to be able to take the torque of the big cubic inch engines on the heavy chassis-ed cars.
1965-1970 were usually 31 spline for the big cars.
1971-1977 the axles were decreased to 28 spline in size as the power output was also lost SOME OF THE 70'S REARS DID COME WITH 31 SPLINE

EXTRA INFO: THERE ALSO WAS A VERSION OF THIS REAR MADE FOR A-BODY HIGH PERFORMANCE CARS WITH 31 SPLINE AXLES ALSO...SOME EL CAMINO , MONTE CARLO, CUTLAS, GRAND PRIX ETC MAY HAVE HAD THIS OPTION WITH 11" DRUM BRAKES.
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brian79
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Re: 10 bolt/12bolt 8.875 full size

Post by brian79 »

I would be putting this into a 79 Malibu. I believe the 10bolt/12bolt fullsize that my friend has came out of a mid 70's Bonneville and it is a posi unit. Don't know the gears.

My ? is to put it into the G-body what does it take? Do I use the 8.5/12bolt conversion upper control arms,shorten the drive shaft,and use 5.5bs on the rims and be done or is there more to it?

If Fabcraft makes a 4:10/4:30 for it that would great or I guess I could use nitrous out of the hole to get it moving if all i had was 3:42.
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monzaz
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Re: 10 bolt/12bolt 8.875 full size

Post by monzaz »

Yes they are strong...BUT no aftermarket gear support. And the best gear that GM installed in the rear was 3.42. MOST however were installed with 2.29 2.73 gears far from performance application. PLUS you will have a VERY wide rear to deal with and the lower and upper control arms and shock mounts will all need to be modified. Just seems like a lot of work for a substandard fit.

We do carrier the custom upper control arm double adjustable for that application for 145.00 then at least you will have that solved the rest is cutting and welding modifications. Jim

BUT Yes the rear is more than strong enough to to the job with a lighter g-body car.

We make a great 10 bolt 8.5 custom diff and axle package that will save you all that work... 250.00 for a bare raw housing and 300 for one totally media blasted primed and Painted chassis black

Moser axles will be 239.00 if you want that taken care of too. which is cheaper than going straight to moser.

a WHOLE COMPLETE BOLT IN REAR TO YOUR SPECS ALL DONE SET-UP WITH CORRECT DOUBLE ADJUSTABLE CONTROL ARMS 1399.00 done!
Attachments
73 -77 conversion g-body arms.jpg
EBAY 2 6 2009 010.jpg
rear diffs 028.jpg
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Re: 10 bolt/12bolt 8.875 full size

Post by sleeve396 »

Re: custom rear?
Jim am I correct in understanding that you can set up the more popular 8.5 corporate center sections and add in the original tubes and brackets from the cars existing rear?
In my case I have a stock 8.2 rear housing that fits my sons 68 Chevelle that needs beefing up to 8.5 size.
The 8.5 is so much more available as internal parts go plus a lot stronger, He has not been able to find a chevele 12 bolt that is not in need of total rebuilding.
Is this a viable option
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monzaz
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Re: 10 bolt/12bolt 8.875 full size

Post by monzaz »

we have 10 bolt 8.5 rears that will bolt right into your chevelle...Please if you have a powerful engine do not back it with junk used trans and rear diff parts. Your just going to spend more in the long run...And maybe end up hurt or strained some place you do not want to be.

Save your money up and do it right. Jim
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sleeve396
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Re: 10 bolt/12bolt 8.875 full size

Post by sleeve396 »

Jim, this sounds like a winner, Can you break down what the rear consists of? Specifically the housing, is it an modified late model or actually an 8.5 rear that happens to fit the 68-72 body?
Also an idea on cost?
I am looking for a dependable rear for mild saturday nite fun and street use, no slicks, I was thinking a 3.42 or 3.55 with an eaton posi. But I am open to any suggestions
Thank you very much.
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