2000 instrument panel buzz

2000 Merc GM has horrible buzz behind the instrument panel when going in excess of 55mph. the faster we go the louder it buzzes. Sounds like the odometer cable. has anyone had this?? possible recall or simple fix?

No odo cable, not since about '90.

wonder what in the world is making all of that racket then? sounds just like gears humming, and it doesnt do it on wet days