I re-checked the left front (where the sound appears to be coming from) and repacked and tightened the wheel bearing. I'll do the right today after work. On the way to work today, it took several miles of quiet before the "drone" began. I tried to turn the wheel to discern if it went away depending on left/right turns but could not come to any conclusions. The drone goes away with reduction of speed...so it has something to do with the moving of the vehicle. I can't believe it is related to my changing out the brake disk since I had completed the job a few days before the sound appeared - unless it took a couple of days for the potential absence of correct amount of grease to "show itself" through this noise.

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Woody