jack the rear end up and shake the tires left and right if you hear that same kind of noise it is the outer bearing. Then push the tire in and out and if you have more than a quarter of and inch of slack that way it may be bad keepers in the drive axle. then if that all goes well then put the truck in drive and accelerate slightly and listen carefully for any grinding or popping, if you do then its the rear end. If all passes inspection then something possibly overlooked like the bumper,spare,leaf springs,or dust cover as listed earlier. Hope this helps
Jeff

 

Thank you will hopefully try this, during my weekend off....