Grinding Rear Noise..Spindle bearng??..next step?

99' XJ, 4.0, AX15, NP231, Chrysler 8.25, 3.07 gears, nd D30

I have had a "grinding" noise since I bought my XJ. Most noticeable between 30-40 mph. Also get a vibration that "seems" to be from left front area although I don't believe it is. Changed all fluids this summer and didn't notice any damage or abnormal wear...although I'm not an expect here. I did notice that the DS input to the spindle on the rear diff was dry and now it is damp. It has always had some wetness at driver side carrier bearing on rear diff also.

So I put the rear on stands and let my wife run it.....turns out the sound can be heard much better from the inside than the outside. Checked all U-joints, rubbers are all good and no movement on DS so assumed ok. I removed the tires and drums and the "grinding" sound is still there although more noticeable around 50 mph. Is it my spindle/differential?

I just read the posts on "C 8.25 growling".....looks like I may need a rebuild on the C 8.25. When I got the XJ the diff cover was very wet and when I finally got around to checking the fluid it was really low......the cover had peeled back....so I replaced it.