Possibly a rear pinon bearing, or if its a two piece driveshaft a carrier bearing which is in the middle of the two halfs.
You could jack the truck up in the rear support it on jack stands and place the truck in neutral and spin the rear tire and see if you can duplicate the sound. But my guess is once of those two items but its hard to say without seeing or hearing it.
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Wednesday, October 10th, 2012 AT 12:45 AM