Bad Bearring??????

[ARTE27]

MY 02 7.3 CREW HAS 50k AND MAKES A GRINDING SOUND @ LOW RPM'S ABOUT 30-40MPH,WHEN I LET OFF OF THE GAS PEDAL.WHEN I GET ON THE GAS I CAN NO LONGER HEAR NOISE,NO VIBRATION,TIRES NEW AND BALANCED,U-JOINTS AND CARRIER BEARRING REPLACED,I THINK THE NOISE MAY BE FROM THE REAR BUT NOT POSITIVE.........HELP