Thanks guys,
I surfed around YouTube to get a feel for what's involved at the axles and bearing(s).

The diff case is 742.

Before I read your suggestion NOT to drive the car, I went and drove the Satellite home and observed the following during the drive;
- The exhaust is too loud to hear much from the rear until I'm going 65mph, and the "RRR" sound is clear.
- The sound changes a little in corners, but doesn't go away.
- The sounds vanishes almost completely when braking.
- At low speeds the sound can be heard just a bit, and it seems to go away taking right turns, but not left turns. Hard to tell for sure though.
- The temperature of the wheel hub on the driver's side is warmer than the passenger side. I'll check brake shoe advance mechanism on the passenger side.

I loosened the lug nuts but kept the tires on, and jacked the rear up off the ground. The lugs are tight enough that the rim isn't loose:
- There is some "play" in the rear wheels, it is about equal on both sides and I detail it as follows:
- I grab the tire tread top and bottom and did Push/Pull get about 1/8" of play.
- With the same grip on the tire treads, I tilted it up, Tilt it down, Tilt it towards the front, and towards the rear. Each side had some play in most directions - enough to make a tiny "clunk" sound when wrestling the tire with my hands.
- Rotationally I get 1" of play before the driveshaft or opposite wheel moves.

The play is enough that if this was my front, I'd be tightening the wheel bearing end-play nut.
I WILL CHECK the level of oil in the case, somehow it "sounds dry" in there. Can't explain why, it just seems harsh, not dampened.

After that, I'll take the wheels off and get a look at the play of the shaft at the bearing plate area. So that might reveal something.

If nothing shows up clear, I'll run the engine in D and listen for the problem.

So far haven't messed with the driveshaft U-joint.

I'll come back here in a few.
- Art