I have a newer (purchased 10/11, build date 08/11) 2011 E350 matic sedan that produces a slight but distinct (just enough to be annoying) whistling sound at higher speeds. It becomes most noticeable at about 70 mph. We left the car at our local dealer for a couple of days, and upon inspection they said its not the transmission, and most likely was a wind related noise. One of the advisors said it may just be a characteristic of the car, that most people don't hear since they have their radios on. I don't feel that fits Mercedes "Das beste oder nichts" philosophy. (Another dealer had said they had experienced the same sound on an S class and it was from the fluid sloshing around in the torque converter. They said it was just a characteristic of the car and couldn't be fixed). Since the sound appears at the same speed no matter what the outside wind conditions (e.g. going into a 30 mph headwind, or having a following wind), I think it is unlikely to be due to the wind. Another post on this forum mentioned something about the seal on a heater box. I would appreciate any suggestions members here may have to offer.

If the noise disappears when opening a side window, the sunroof drain grommets “may” be causing the problem. Reference bulletin LI83.00-P-051420 recommends grommet replacement to current part # 0019989301.

I'm always whistling when I drive, and always wonder if people think I'm blowing kisses at them............

Does your car have panoramic roof ? If yes #$$#$% I should have deleted this option in the package lol

I will try to lower a side window the next time on the freeway to see what effect this has. The car does not have a panoramic roof, so that is not involved. One other important item, not mentioned above, is the fact that the whistling sound stops whenever you take your foot off the accelerator pedal. This when traveling between 70 and 75 mph, when the sound is most apparent, it comes and goes depending on whether there is pressure on the accelerator pedal or not.