My 190k mi. 300E just developed this problem (of course because I have a big trip planned today). I looked for the cause and had the wife help. Seems to be from the lower conrol arm pivot (ball joint).
In one diagram it seems like that part is replacable. the sound I have is on the lelft front only. When the car is in the air there is only the occasion faint sound, on the ground it's so nasty it's scary!
Can that lower ball-joint be easily replaced, anything else I can check and why don't ANY of the joints have grease fittings...
TIA!!!