'84 380SL, 200k miles, new flex discks & center drive shaft support & bearing. There is a noticeable vibration from drive shaft, it comes & goes. I tried moving the differential pinion and it has radial play. Is this responcible for the vibration? What is the course of action? Differential overhaul? I have good knowledge of gearboxes and know about backlash, gear mesh and drag. Can I perform the O/H myself?