I have a 53 3600 long bed with a 4speed tranny.

I assume the rearedn is an Eaton with a low gear ratio.

How do I know the gear ratio?
How can I identify if this is an Eaton and if so what model?

There is a number stamped on the diff.
8699565 (or could be 3699565)and under that a smaller 344.

Any clues to what this is?

1953 3/4-Ton Chevy

In the Stovebolt Gallery
More pix

If it can be built ... It can be fixed.

RB53