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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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#81343 08/12/2007 3:19 AM | Joined: Nov 2004 Posts: 117 Wrench Fetcher | | Wrench Fetcher Joined: Nov 2004 Posts: 117 | I've got a '72 C10 with a stock 12-bolt GM corporate open rear. Gonna be rebuilding the rearend anyway and would like to upgrade to a posi as long as I've got it apart. Are 12-bolt truck rears pretty much all the same? That is, if I found a posi out of an '80 Blazer (for example) with a GM 12-bolt, should it work in my '72?
Thanks,
Brent | | |
#81344 08/12/2007 3:29 AM | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | If it's a 12 bolt truck diff, then yes, it'll work. But you'll need to be looking for no later than about '77. GM went to the 10 bolt after '78 for most 1/2 tons. Also, be wary of pre '63-'65 diffs, they use a different spline (17 instead of 30) with a mid year change in '65. If you truly want a Posi, check out the aftermarket. Lots of choices available, new, plus gears if you want to change the ratio.
Bill Burmeister
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#81345 08/12/2007 3:40 AM | Joined: Nov 2004 Posts: 117 Wrench Fetcher | | Wrench Fetcher Joined: Nov 2004 Posts: 117 | Thanks for the info! For right now I am forced by finances to avoid any really decent aftermarket stuff (Eaton, Auburn, etc.) but GM posi's seem to be available at reasonable prices. It's not necessarily a permanent solution but as long as I'm in there I figure it would be a shame to not at least consider a posi. :-) | | |
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