Grinding Noise From The Rear

I'd check your u-joints first, a binding joint could show up when you're loading or unloading the rear (accelerating / decelerating) as the pinion angle changes. There are obviously a number of moving pieces in the rear that could cause grinding (wheel bearings, carrier bearings, pinion bearings, or the ring & pinion itself) but the vibration is less common and might be the u-joint. My '95 with fairly low miles had one of the u-joints go dry after a number of years and bind causing vibration as well, though no grinding sound. You might also check for dragging rear brakes (a frozen slide is also pretty common). Beyond the brakes or u-joints, it gets more complex (and expensive).