I dont have any background on the machine, but sounds like something that I ran into not too long ago on an old westinghouse 38 with a flange mounted AC motor. The problem we had was that the motor sounded like the bearings were bad. it was not the case. I tore the motor down and replaced the bearings and even replaced the rear thrust bearings. did not solve the issue. finally I noticed that the taper lock on the coupling on the motor had worked the grub screws loose just a hair and had pushed the two couplings on motor and gearbox(the ones that have the neoprene like ring like a spider gear) together too tight. I pulled the motor, moved the taper lock and coupling back away from the gearbox about 1/8" and it fired right back up with no noise. The two were barely rubbing together metal on metal and not allowing the motor to find its balance causing a grinding or squealing noise. Might not be your problem, but its a suggestion.
