humming noise in the rear

i have a 2001 classic 4x4 and its had a humming noise from the rear ever since i got it in january. At first i thought that maybe the rear brakes were to tight and checked and adjusted them. noise was still there. so next i changed my rear diff fluid and looked at the gears to see if anything is warped or broken, nope. noise still there is there any other suggestions of things i should check? oh the rear drums have a groove inthem from the old factory shoes could that be it? thanks

A humming noise at what speeds, and under what load?

it does it under normal load from start to stop at any speed. thats what made me think brakes

probably uj going south

That was my thought too, although I normally don't hear 'em hum until over 35mph or so if they're a problem. Definitely a cheap and easy fix to try.

Maybe also a slightly bent/dented driveshaft, or it could have thrown a balance weight.

thats what i was also thinking was the driveshaft b/c as the speed increases the noise with get a higher pitch. that would probably be some helpfull info. but thanks for the info so far i will check my joints