HUGE UPDATE.
After 2 years of whines and now a loud rumble I took the car to yet another mechanic. This time he is a retired tire and suspension guy and he diagnosed the problem an old school way. We took the car out on a back road with a hill, he sat in the back seat and as we started down the hill I popped the car in neutral and shut off the engine. Bingo, right rear wheel bearing screaming away. Yesterday he replaced it and the car is now stone quiet, well a little noise from the cupped tires, but I can live with that till the new ones come in the spring when I take the snow tires off.
Thanks for all the comments, you guys are great!
Mark