Electric motor makes loud grinding sounds and vibrates badly

It could be your armature bearings need to be cleaned and repacked with grease or heat has caused the windings of the armature (shaft with wire coil attached) to wrap and needs to be to be rewound. Worst case is the armature shaft could be bent. You will have to disassemble the motor to get an Idea what the problem is. Clean the bearings and armature and look for contact rubbing on the armature and magnets. Check the shaft for balance and shaft straightness.