I saw this online and was wondering what kind of differential it is. The guy who owns it says it came out of a 55-56 Dodge Custom Royal Lancer. How does this differential differ from the rear ends in the 60's. What's the specs on these diffs? Drum to Drum length? Length between spring perches? Etc.? Just a little curious.

I can't see the end of the axle, but based on the flange on the driveshaft connection and the description, I'm betting that is what was considered a Chrysler Corporate rear axle.

It is about the same size as the 60s 8 3/4 but nothing interchanges. It likely has a gear ratio in the 3:70 - 4:10 range, is an open, or peg leg center, and has a tapered axle with a keyed flange held on with a large nut. The issues are the axles with the keyed hubs. They are a pita to do anything with brakes because the hubs need to be pulled to gain access to the brakes. Pulling off the hubs requires a very beefy puller and is often a battle. If traction ever happened with an open axle, the key might be a weak point. They do tend to be a bit more narrow in width then modern axles. I don't ever remember hearing of them actually breaking, but most people upgrade them to 65 and newer 8 3/4 rear ends because of those tapered axles. Gene

That's interesting. I never thought about the rear ends in the 50's cars till I saw the ad on CL. You learn something new every day. Thanks for the info!

Actually, that rear end, or one of very simular design (at least they look the same) has been around since at least the 30s!

Much like the old flat head 6, which kept the same basic design from the very early 30s through the early 60s in automotive production and through the 70s in industrial applications. Mopar didn't change things that functioned well, they may have upgraded things, but seldom flat out changed things unless the new design was much better then the old design. Gene

Not all rear ends from the '50s were weak. The '57 - 64 Olds/Pontiac was the axle of choice in the '60s.

R.

Count the number of nuts holding the 3rd member to the housing, if it's eleven, the rear end is an 8 1/4" (the 8 3/4" has ten nuts).

These were used from '37-'61 and the ring and pinion lived on through '64. The axles on the pre-'57 had 16 splines.

John, is there anything you don't know?
R.

i saw a diff like that on an original--- rusted solid--- 1933 plymouth 2dsd---it looked like an 8 3/4 but i didnt explore further---so it may have been an 8 1/4 with a drop out center section.....very interesting