I have this sound too and nobody can tell me whats wrong. Mine is a 1997 C180 with a 722.6 I think, six speed auto. Mileage is 226,000kms. It whines in low gears as I drive off, 1,2 and in 3 and higher it disappears. Therefore its speed related. No noise in neutal or when at stop. If in drive but stopped, there is a rear push felt and a slight rattle many say from the drivebelt tensioner???