My wifes,98 ML320 has developed a vibration, buzz, rattle, what ever you want to call it. It occurs at 20 MPH and at 40 MPH. Rough roads to not make it buzz. Turning, accelerating, stopping has no effect. It will not do it standing still and will not do it running with all 4 wheels in the air. It sounds just like the left front brake dust cover vibrating, or a heat sheld on the exhaust. It is a metallic vibration sound. I have been over all the shields and body panels looking for this and if I had hair I would have pulled it out by now. Any suggestions, thoughts, directions to look. I am desperate enough to start paying the dealer to look for this and that I can not afford.

Is there something in the drive line that could do this? The shafts all seem tight, no clunks or any other strange noises.

Thanks in advance.