rear end question

[Philossifer]

mustangdaren,
If your bearing are shot at the axles or the pinion, eventually the seals are going to leak and you'll know it!

I think your problem might be (internally) with the differential.

You can take it to a shop that specializes in rear-ends and they'll do an oil change (which usually includes a visual inspection of the rear-end) for about $45.
Phil