Well, I think this truck has the same rear axle as my 61, but i don't know for sure (check the link for pics). If it does, the fill plug in the rear cover should be below the midpoint. I think the theory is that as the gears spin, they will sling the oil all over the place, and lube everything. On mine, I don't see any way how all the oil could drain out of the hubs and back into the differential. It would have to flow up hill, which, last time I checked, doesn't work too well. Maybe somebody with a 50's era truck could back me up on this???
Do you use the e-brake? Are the temps cold? I have heard of cables freezing up, not letting the truck move. Try backing into your parking space. Does the other wheel lock up? Could the brake shoes be adjusted too tight? Just a few thoughts.
