The noise is from the motor. The machine turns over very freely by hand. I have disconnected the belt from the motor and run the motor with no load. It is smooth with no load. If I hold the pulley firmly with my hand and step on the pedal, there is a lot of vibratory noise. I think it is the windings. The brushes on this motor can't be serviced externally. In order to disassemble the motor I'll have to remove one or both rivets holding the Kenmore tag across the motor halves. I have been reluctant to do that because it may be a challenge to reassemble the motor while holding the brushes out of the way. I have had the motor off and looked at the commutator, and it looks great. I have used my drill press as a lathe and turned the commutator on another sewing machine, a White 651. It runs great so far.