Scored a 57 rearend how is it different than 55?

[rockytopper R.I.P 5-13-2017]

Ok I bought a cheap 57 rearend. I plan to have it completely rebuilt with eaton limited slip, 3.08 gears and new axles. Just curious of the difference in it and my 55 in the mad?
Thanks
Rocky

[Maddog]

Uses different wheel/axle bearings, maybe the drain plug is different. That's about it. By the way the axel bearings are larger so that should be an improvement.

[Rick_L]

The 55-56 differential carrier is different, as are the ring & pinion gears, which are not reproduced. The gears are a little thinner. An entire axle assembly is totally interchangeable.

[rockytopper R.I.P 5-13-2017]

The 55-56 differential carrier is different, as are the ring & pinion gears, which are not reproduced. The gears are a little thinner. An entire axle assembly is totally interchangeable.

So your saying the after market stuff is 57 and on right? They list the kit for 55-64.
http://www.ebay.com/itm/1955-1964-GM-8-2-55P-CHEVY-CAR-3-08-RING-AND-PINION-EATON-POSI-GEAR-PACKAGE-/272015547555?vxp=mtr&hash=item3f5563dca3

[Rick_L]

That kit should work fine.

But you couldn't use the posi unit without changing to 57-up gears too. And you couldn't use 57-up gears with a 55-56 differential carrier.

[rockytopper R.I.P 5-13-2017]

That kit should work fine.

But you couldn't use the posi unit without changing to 57-up gears too. And you couldn't use 57-up gears with a 55-56 differential carrier.
Understood. Thanks!!!

[chevynut]

The 57 axles and bearings are different than 55-56 and the 57 housing has a drain plug, which is absent on a 55 or 56 housing. That's the easiest way to tell them apart. They're functionally the same.