Motor Question (Sound Clip)

[crazyjr]

The sound i hear sounds like a vibration from a worn bearing. When i raced slotcars i heard it a few times when the bushings were about to wear out. It only happened when not on load like yours does. I would look at getting a pair of bearings, just in case. Not sure how long you have, but not tring to worry you, just my experience. Never heard that from a bearing though