have you checked your wheel balance? A loose shock shouldnt cause a vibration. Could be an outboard u-joint, wallowed out track bar mount, worn tires, seperating plys in a tire... any number of things. A loose shock is not great for the ride but it would cause more of a bounce than a wobble.. good luck with the search. Please dont be that guy that beefs up the steering stabilizer to remove a vibe. That only masks an underlying problem.