Axle hum

I have 97 Jeep cherokee the rear axle seems like a high-pitched hum when I'm driving normally around 40 to 50 to 60 but when I'm on the highway kind of disappears. Any ideas?
The gears look fine last time I cleaned the diffs out if that helps

I'm hoping for a wheel berring but figured I would ask to see if anyone has any other ideas !?

My guess would be bearings.
Not too hard to swap them out.

I had a bearing start to go once, but didn't hear it at hey speeds - till I drove past a long section of wall and heard the echo to let me know it was

Yeah, I'd agree that son long as the gears look good... that it'd most likely be bearings going out... And as Dave said... they're not too hard at all to change out.. get em swapped out and see if it takes care of the issue.. if nothing else you'll know you got new bearings in there

Often, I only know I've fixed the issue...
...because I've replaced every possible piece.

And then you start on the next issue