2000 Silverado rear end problem

I recently began to hear a "whining" or "howling" noise coming from the rear of my 2000 Silverado 4x4 at around 65 miles per hour. It seemed to become louder when you tried to accelerate to maintain your speed. The noise was considerably less if you took your foot completely off the accelerator. Could it be an axel bearing or a bearing in the rear differential? Sounds like it is coming from that area. Any help would be greatly appreciated.

does the noise go away when you hit say 75? it's probably the ring& pinion gears. mine does this i learned to live with it. come to think of it every chevy i've owned has had a diff howl. usually a bearing makes noise whenever it's turning but the rears tend to resonate at around 65 if their just a little bit off, if you have a canopy the noise sounds worse. the only fix is to replace the gears which thats a big hassle. or get a diff from a junkyard with the same ratio.

My 2000 Silverado 4x4 w/75xxx miles is doing the same thing.

my 99 had the same noise. bearins went bad, melted to races, races started spinning in housing .

new housing,bearings seals. $3800