If motor still runs noisy or hot, replace bearings. Reduce overload or install larger motor. Locate source of vibration and reduce. Check brushes and brush holders. Does each brush fit commutator as indicated by polished surface over entire brush face.
Refit brushes to commutator.
Clean brushes and holders. Remove rough surfaces that cause extra friction. Replace spring or increase pressure. Be sure pressure is equal on all brushes. Reset holders at neutral.