I too experienced this problem with my new GLE350 SUV and got it RESOLVED! But first the background: Went to dealer last summer and test drove a new 2015 ML350. Since the new 2016 GLE350 was soon to be available, I opted to custom order it exactly like I wanted and wait for delivery. When my new GLE arrived a few months later it sounded much more raucous and louder than the ML I had previously test driven. My new GLE had annoying exhaust resonances at low rpms, 1500-1800 and then around 2500 which unfortunately is right where the rpm sits at 70 mph, so it just droned away as I feathered the gas pedal to maintain constant freeway speeds. Passengers often remarked about the sound... "is your car OK .. sounds funny" ...
I took it back to the dealer for its first checkup and complained. Initially got the 'it's normal ... that's the way it is' response. One story was that it was intentional to be more 'sporty' sounding. But after putting several thousand more miles on the car I had enough and wrote a letter to MBZ North America. Dealer called me shortly after to bring the vehicle back in for them to take another look at it. This time they drove the car longer and consulted with their PTSS (product technical support system). They concluded this was an exhaust resonance that could be heard and felt as a vibration in the vehicle. They kept the car for a few days and repaced the rear muffler. According to the service record "per PTSS installed an earlier production rear exhaust with turned-down exhaust tips..."
I crawled under and confirmed the entire rear muffler assembly was shaped different and brand new. The exhaust tips no longer enter the decorative chrome 'faux' exhaust ports at the rear bumper. Now they are turned-downwards just in front of those parts. This definitely did the trick. Car now drives much quieter and as rpms pass through those previously noisy ranges, the exhaust stays quieter without the loud resonance.
