That is not a good sign. Usually slow speed or slow start is included in the symptoms. The motor will need to come apart. Be sure to mark it so all goes back in the same direction. The top and bottom bearings are sintered bronze. They were semi permanently lubed but now there will be a green colored grease that comes out if you stick a q tip and some solvent in the holes. It's very difficult to remove all the grease but it is possible by heating the bearings and stuffing them with cotton. You can buy a kit on ebay to replace the motor bearings. There's a bit more to it but this will get you started.