i got a 2002 gmc serria 5.3 z71 auto i get a humming sound between 20 and 60 only when im not on the gas just riding or with the cruse on i cant tell where its comming from it sounds like the rear end but im not sure does anyone know whats going on? i chanded the trans and t case fulid i havent done the front or rear end yet some one told me it was probley the locker but it works fine so i dont see where it would be bad?

 

Sounds like pinion bearings in your rear end. It will need to be diagnosed by a mechanic though because other parts can be faulty. Wheel bearings can also cause this noise. Don't start spending money until you find out the problem.