[weim55]

One of the bearings in the differential is the likely culprit. What happens is as the inner race is rotated The bearing rollers and the outer races are turning at different speeds from one another and when the 'bad' areas aline a vibration or noise similar to what you are describing occurs. The main culprit I've noticed for this is rust pits on one side of the bearing from our trucks sitting for extended periods (years) of time. Because the pinion bearings are the highest in the housing (oil starved) they are the most likely to have this issue.

The part of your description that doesn't add up for me is you claim the vibration is bad enough to vibrate mirrors. I've never seen a differential bearing issue bad enough to cause that but it wouldn't be impossible.

Steve weim55 Colorado