i had same issue on 83 300sd. was the strut rod bushing. hard to detect the problem as there is so much pressure on the apparatus there will seem to be little play/wear.usually the bushing (which is like a big ball joint) will have its rubber cap torn ,letting in water/dirt & wearing out the metal. not an easy repair but can be done on driveway as i've done it 3 times over the years. if done at the dealer you pay dearly