Classic/Antique Car Repair: Noise from rear end

Question
Brad,

I have a 1940 Hudson standard shift. I currently have it up on jack stands to do some work on the brakes. Since I don't have it on the road I start it regularly and I put it through the gears just to exercise the old car.
While doing this I have noticed that there is a humming noise coming from the rear end. I have not yet checked the fluid level but I am wondering what that noise indicates? Could it be something as simple as fluid or does it mean the pinion and ring gear are worn? If it is the pinion and ring gear can they be replaced?

Thanks,

Answer
As strange as it may sound, you will hear more noises when the car is on stands than you will driving down the road. That said I would make sure that all the fluids are up to snuff and then wait till you get the car on the ground and listen for noises. If it is the ring and pinion these can be replaced and the rear end rebuilt. It is something that we did all the time back in the day. And yes I was working as a mechanic when you 1940 Hudson was just a used car that would show up at our shop for repairs.