GM 8.5 ring/pinion interchangability question

[garys 68]

I've got a 72 chevelle 10 bolt rear with 2.73 gears on my LS swap 72 Olds DD. I want to change out to 2.56 or even 2.41. I'm running a T10 with 3.42 and it gets lots of hiway driving.
Are the ring/pinion on all GM 8.5" 10 bolt solid axles interchangeable throughout the years? What about carrier compatibility?
I'm debating between changing the gears in the current housing vs buying a used axle with 2.56 gears (they tend to be really cheap around here) and only need to rebuild brakes, bearing, seals.

[Skip Fix]

8.5 carriers change at 2.73s. So a 2.41 and 2.56 use a different carrier than a 2.73 up. The 2.41/2.56 carriers are pretty cheap if you find one as most guys want better gear choices. Down side is they are factory carriers and only recently has someone made new clutches available to rebuild them.

Are you sure yours has an 8.5? They were only factory in buick olds around '72 not Chevies. Chevies and many other earlier A bodies used an 8.2.

[garys 68]

I think you're right on the 8.2. The 72 chevelle rear end is on my 72 Olds cutlass. I thought the chevelles swapped over to the 8.5 along with the BOP cars around 1970.
Just peaked under no lower tabs, cover is aftermarket chrome but has the diagonal crease.
Just going to pick up a whole 70-72 2.56 rear axle. They're cheap anyway.
Thanks!

[Z06vet]

I have a 2 series posi unit for 2.41/2.56 gears if you end up needing one for an 8.5.
Scott

[garys 68]

Not sure if there's a 62.5" wide 8.5 axle with spring coil mounts. Thinking I'm stuck with the 8.2 and 2.56 gears.

I have a 2 series posi unit for 2.41/2.56 gears if you end up needing one for an 8.5.
Scott

[Skip Fix]

62.5? where are you measuring that? Measure from backin plate flange to backing plate flange. Should be closer to 55" or so.

Pretty sure most A body rears swap, 65-67 are a click shorter than 68-72 but mounts are the same. Monte Carlo/Geand Prix bolt in too.

[garys 68]

Going by this chart:
http://www.carnut.com/specs/rear.html

[Skip Fix]

That must be drum to drum. Most GMs are 2.81" from backing plate flange to axle flange so almost 6" to a 54" housing gets 60".