Originally Posted by Skyline

Given the low failure rate of these, why not get a diff from a junkyard?

Also, given the symptoms, I would want to take a close look at the intermediate driveshaft bearing, (in the middle of the rear driveshaft). Those DO have a high failure rate, and can cause similar symptoms. If there are any tears or cracks in the rubber ring, replace this before considering a diff. Take a look at the guibos as well.