I'm not going to disagree with anyone but this is the one experience I've had with this. Bought a W200 with the 4.10 Dana 60 in it. Drove it 500 miles home with the rear end singing the whole way, both on acceleration and deceleration. After about three months I finally crawled under it and found the pinion end play to be over 0.050" (that's no typo). I set the entire rear end up again from ground zero and drove it. Now it sung on deceleration but not acceleration. After about 50,000 miles it's quiet in both cases.