I have this rear axle that I originally thought was Olds/Pontiac of uncertain vintage. I've spent some time searching this Forum, as well as Googling the internet. I've found some pictures that look close, but have some minor differences in the rib configuration. Does anyone know for sure what this is?
Yep, Olds or Pontiac will have a 5 on 5 bolt pattern with 1/2 inch lug bolts. Chevy will have a 5 on 4-3/4 with 7/16 lug bolts. Looking at this one on Ebay eBay item number: 263455750450 Yours has a lot of similarities third member wise.
Yeah, it's early. Does look like a Pontiac, '53-'62? Good thinking on lug pattern check, Desmo: Measure from the center of #1 lug bolt (1 of 5) to the far side of #3. Center of #1 to far 'edge' of #3. That will tell you if it's 5", 4-3/4", 4-1/2, etc. Then tell us.
Here is an old thread on the subject that might help https://www.jalopyjournal.com/forum/threads/pontiac-olds-rear-end-id.105783/ One thing to quickly cut down the hunt is does it show that it had brackets for control arms for coil spring rear suspension or does it just have or show that it had leaf springs? That would id it as 57 or earlier with leaf springs or 58 or later with coil springs.
It is Olds/Pont, post 56, so 57-64 "style". It has the "two rib" support third member, and not the "better", "three rib", third member; I think the split was 58 when that change occurred. IF the housing has leaf spring mounts, then it could be a 57 Pontiac housing (direct bolt in with existing leaf springs for a Tri-Five Chevrolet), or 57-63 Olds leaf spring, although they are not a direct Tri-Five Chevrolet swap as the spring pads need to be moved. There's also some minor differences in housing/axle width over the years. 39-56 Olds/Pont used a different style flange that used a bolt-on trunion for the U-joints, and not the U-bolts 57 on used (as your axle has), and although they look similar, the 39-56 rear axles are "smaller". So basically, a 57 -64 (full size), Olds/Pont. I am Butch/56sedandelivery.
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