xviper

This would indicate to me that you bought the car used and it has "history", right? In that case, yes, best to get it checked out. Might be nothing, but you just never know.

speed4tu

If you have a whine with the stock gears, def. get that looked at. Mine started to whine about 3000 miles ago, and about 3 weeks ago my whole diff. split in 2 top and bottom. Today I took my old diff apart to see what went wrong. I don't know the name for the stuff in there, but gear with the shaft on it looks like what broke. A few of the teeth broke off of it and broke parts of all the gears.

Ludedude

Yep, that would be the pinion gear and seems to be emerging as the most common cause of diff failure. Interesting about the case though...I wonder if that broke as a result of the gear failure or vice-versa.