I have 2004 sierra 3/4 ton crew cab 4x4.Started making whirling noise the best to describe it toward the rear of truck.Inspected diff looked good put new gear oil in it.The noise comes as soon as drive shaft turns on jacks or moving.Took stethescope could not find any unuseaul bearing noise.Removed brake rotors and calipers to eliminate any rubbing issues still there.I read on the internet people with same issue but no answer.Put 2 new u joints in hoping that would solve it.Truck only has 76000 miles on it.
