Check for slack or noise coming from the rear end pinion gear bearings. Jack up the rear end and support it securely on jack stands, or put the truck on a rack, and have someone "drive" it at a constant speed, then slow down while you use a stethoscope or a long screwdriver to touch the rear end housing just behind the driveshaft yoke. If there's a bearing failing, you'll hear a loud grinding noise that changes from pull to coast, and might go away or reduce in volume significantly at a "float" neither pulling nor coasting. Be careful to stay away from moving parts like the driveshaft while you're probing for the source of the noise.
Jerry
Last edited by Hotrod Lincoln; 02/19/2011 3:26 PM.
