Spindle, Spindle Housing and Bearings
(1) Check the two spindle housing oil cups and determine if the unit has been regularly lubricated. If it hasn’t, a light growling noise should be present. (2) Check the air gap clearance between the rotor and stator to make certain they are not rubbing…if they are, either the spindle assembly bearings are no longer holding the spindle/rotor concentric within the stator or some mechanical damage has occurred to the rotor & stator.