72 Blazer 4x2... what in the 12 bolt? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OC Short Box · 03-31-2011, 01:50 PM

Hey guys. Need help with identifying a 12 bolt rear diff. Im working on my buddies 72 K5, and it looks as though somebody swapped in a 1/2 ton 12 bolt that used to have axle perches on the top for leaf springs.(no longer there) I cant I.D. it first off, and second. It has a different wheel bolt circle diameter.

What diff should this thing have in it? (bolt circle and ton rating)
Can I easilly swap in the right axles from a 3/4 ton diff if thats what it needs?
and lastly, does anyone have the parts or diff I may need for sale?
Thanks! OC Short Box

SeventyOne · 03-31-2011, 03:01 PM

A corp. 12 bolt was the stock rear axle in 69-72(+) Blazers. It's a 1/2 ton unit.

If yours is a 4x2 it would have trailing arms instead of leaf's but it may also be a 4x4 to 4x2 conversion...

OC Short Box · 04-01-2011, 01:50 AM

It has the trailing arm set up, and no evidence of leaf springs, but the front K member looks like it had 3/4 ton style lower control arms mounted originally. Repairing someones butcher job of 80s lowered control arm set-up now... Thanks for the corp.12 info. The diff in there now has that weird "swoosh" patern in the cover instead of smooth and round.

03-31-2011, 01:50 PM	#1
OC Short Box Registered User Join Date: Jun 2010 Location: Orange County California Posts: 10	72 Blazer 4x2... what in the 12 bolt? Hey guys. Need help with identifying a 12 bolt rear diff. Im working on my buddies 72 K5, and it looks as though somebody swapped in a 1/2 ton 12 bolt that used to have axle perches on the top for leaf springs.(no longer there) I cant I.D. it first off, and second. It has a different wheel bolt circle diameter. What diff should this thing have in it? (bolt circle and ton rating) Can I easilly swap in the right axles from a 3/4 ton diff if thats what it needs? and lastly, does anyone have the parts or diff I may need for sale? Thanks! OC Short Box Last edited by OC Short Box; 03-31-2011 at 01:51 PM. Reason: thanks :)

03-31-2011, 03:01 PM	#2
SeventyOne Registered User Join Date: Mar 2007 Location: Oakland, Ca Posts: 1,382	Re: 72 Blazer 4x2... what in the 12 bolt? A corp. 12 bolt was the stock rear axle in 69-72(+) Blazers. It's a 1/2 ton unit. If yours is a 4x2 it would have trailing arms instead of leaf's but it may also be a 4x4 to 4x2 conversion...

04-01-2011, 01:50 AM	#3
OC Short Box Registered User Join Date: Jun 2010 Location: Orange County California Posts: 10	Re: 72 Blazer 4x2... what in the 12 bolt? It has the trailing arm set up, and no evidence of leaf springs, but the front K member looks like it had 3/4 ton style lower control arms mounted originally. Repairing someones butcher job of 80s lowered control arm set-up now... Thanks for the corp.12 info. The diff in there now has that weird "swoosh" patern in the cover instead of smooth and round.



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