I have, but that does you no good, because I don't know anything about the mechanical stuff.
Do you think something could be making contact with the fan? Or the fan could be damaged?
Bearings in the motor could be shot. I'm guessing a bearing because it slows down with the motor. I've heard a few vacuums like that one my parents windtunnel motor was gone and and oreck magnesium likely the motor was gone.