The main pic is on its side- right? So that the crown wheel overload screw is facing up.
It looks identical to the one in my '47 1.5 ton (4100, more or less).
mine is MASSIVE, 12 inch crown wheel, 5.54 ratio, on an axle with 11000 lb springs and dual 7.00-20 wheels.
From what I know, (not much) all the big bolts from the early 40s to the mid 50s had the same unit with varying ratios, 5.54 and 6.11 were common.
No stampings, vague casting numbers between the top ribs.
Rich
