I recently changed the rear Pinion Oil seal in a 98 Explorer. Everything was fine for about 3 weeks. Then there started to be clunking noises (similar to a bad U-joint). I checked the joints and noticed that oil was on the underside of the car near the pinion oil seal I just changed. So I check the level...it's very very low.

Here's the problem. When I grab the drive shaft I can physically move it up and down a little near the rear axle where the driveshaft meets the rear axle. There feels like way to much play. I think that the pinion bearing inside the axle housing might be shot. (I don't even know if there is such a thing as a pinion bearing) Could this be caused by to much fluid inside the housing.

Let me know what you think. This is my mom's car and she has nothing else to drive...so it's really urgent.

It was the pinion gear bearing..thanks for the help.