It may have had a bad bearing, but my bet is the bearing was causing a vibration causing something else to make that buzzing sound. I've never heard a bearing sound like that either.
I happen to concur. The theory developed on the scene was that the roughness of the rear bearing caused it some manner of "galling" (for lack of a better descriptor) at speeds above 45 or so - and that when this galling occurred, something else (likely the shifter adapter plate we found slightly loose) or some such commenced to vibrating and making the buzzing sound. Whatever it was, it was totally gone on the drive home and the transmission shifted as beautifully as it ever had. We'll see with longer drives...
