When I accelerate, there is a annoying humming noise that appears to be coming from the rear-end. It started doing this only on rare occasions soon after I bought the truck but it is much worse now. It makes the noise almost everytime I accelerate. Its starts humming when I begin to accelerate and then stops once I get a little speed, say 20-25 mph. Once I get going, I don't hear it any longer.

 

You're gonna need to take it to a rear end shop. Could be gears, bearings, etc. Need to have it looked at by someone who knows gears and is very knowledgeable in the area.

 

I hadthe same problem, but it would me humming every time I'm moving. Just recently me and my cramps fixed it, it was the bearings in the diff or something, the bearings were chewed to ****

 

prolly carrier or pinion bearings mine are going out so im replacing them and the the 392 gear with 456....