I have the same problem at 208,xxx. But now with my aggressive tires I can't hear it anymore
I put in Lucas 80w-90 gear oil and it seemed to quiet the noise some. I'm pretty sure they are the original axles/wheel bearings so I figure they are just getting old. My left rear wheel seal leaks also, probably part of the problem.
I would also pull the differential yoke to see if that seal is good as well. I've seen other posts on here about the seal to become grooved over time causing noise.
U-joints wouldn't cause a rotational hum/whine.