OK, I've searched the many, many noise questions posted on this forum. No posts match what I am experiencing, so if you can help, please do !!! 2014 E350, 39,000 miles. No problem or noise until I reach 40 MPH. At that point I hear a very discernible noise (whine??). The noise stays the same pitch and volume all the way up to 90+ MPH. The noise stops when I slow to less that 40MPH. It does not change pitch or volume with any variation in road speed or engine RPM. I can't point any specific location but I would guess it's from under the car. Any help? Thanks

 

Drive on a straight road, is the car pulling to direction? You could have a bad wheel bearing. You sharing some similar characteristics, but at only 39,000 it seems too soon for one to go bad unless it is defective. Pretty easy to change.

Does the tone of the sound change when turning in different directions (left or right) at 40+ speeds? That would be an obvious evidence it is the wheel bearing

 

No, no change in noise when changing direction.

 

How old are your tires? Do you rotate them every 5,000 miles? It literally just sounds like tire drone to me, which can be quite loud and not kick in until you hit a certain speed.

 

I had a front drivers side wheel bearing go bad and that produced a whining noise only at high speeds. Could be that?

 

Going to the dealer tomorrow. I'll let you know what he finds. (or doesn't!)

 

But tire noise changes pitch with speed changes.

As the car is a 4-Magic I suspect the transfer case bearing failure that seems to be an issue on many E-Class 4-Matics. When bearing fails and allows the gear wheel to move and rub with the solid part it makes whining noise and it usually does not change pitch with changing speed unless the gear teeth are rubbing too.

 

The change in pitch is almost imperceptible with tire noise. It just gets louder and louder. I bet that’s it. We shall see if you are right.

 

Hooray! Half my problem is solved! Took E350 to the dealer this morning and a mechanic went with me on a test drive. As soon as we hit 40MPH the tech agreed he heard the noise. "May be a wheel bearing or a Transfer Case bearing"..... I was afraid they (dealer would blow me off as a non-problem especially since I am still under warranty! But they didn't! I'm impressed!!!!! I'll update the forum when they are able to track down the exact problem. THANKS TO ALL THAT CONTRIBUTED!!!!!!

 

Looks like Arrie may have called it

 

wow, a transfer case bearing already gone bad at 39k miles! I am kinda disappointed...and nervous, too.

 

You and me both! Let's hope that is not the case.

 

Just got back from the dealer. The problem was a bad left front wheel bearing!!! Fixed under warranty. Thanks to all who responded especially dbldpr who NAILED IT! Good job all!!!!!

 

My car only had about 1000 miles on it when the wheel bearing went out. They did not even stock the part because it was not suppose to go out. Glad I could help. Just a lucky guess

 

Well, good it was that simple. It is odd though that turning the steering wheel did not change the noise. In all cases that I knew so far it was very easy to hear difference in the wheel bearing problem when turning the steering wheel left - right...