ORIGINAL: rexrw
I don't hear the noise unless the truck is running and at pretty high throttle. With the truck off, i I spin the spur gear there is no grinding sounds. Do I have to remove the drive cups to gt the gear box out? What is lurking inside that gear box, is it hard to open and do I need to be aware of anything falling out like gears or springs?
I suspect it's a diff, front or rear. Did you shim your diffs? hard to say sitting here on my computer but since it only happens under engine power torque, I think one of your diffs is slipping. do you have your manual for the truck? it's not hard to take apart the tranny or diffs as long as you pay attention real closely, and label all the parts well(screws, gears etc) and have the manual. even snap step by step pics with a digi cam so you can refer to them when putting it back together