Majority of the fans made now days are non-oil motor bearings. Most likely with it sitting in the garage, the stator developed a dead spot from the resin where the rotor contacted it, may have loosened up if the garage was always warm during the Summers.
There is not much you can do, but get a new one at this point. The motors cost more then a actual fan unit.
There is not much you can do, but get a new one at this point. The motors cost more then a actual fan unit.