so this sound is a low tone almost rubbing type of sound, as if something was out of round and on each rotation it would rub and cause the sound. As you speed up it also relates to the speed but never gets louder. I do notice this sound is primarily only under load. If I reach my speed and coast, the sound tends to pretty much go away until I press on the gas again.

New Rotors and pads, back plates are fine and no visual signs of anything rubbing or leaking.

please toss in your 2 cents on what you think this may be?? Keep in mind that there has never been any repairs to the drive shaft, u joints or rear drive axle and its components other than new gear oil.

thanks,
Ron. 2007 5.3 Suburban LTZ, 242k