Howling X3

[kallad]

I have an 07 X3 w/ 55k that developed a howl when the drive train is unloaded, decelerating (it started at about 52k). You only need to lift the throttle ever so slightly to have the noise. Driving in city traffic and using the throttle lightly just allows the howl to come in and out. The howl starts at about 38 mph and continues down to about 30 mph and seems to be coming from the center of the drive train, and it decreases in intensity as the vehicle slows. It also howls at 76 mph (speed multiple) , but the wind noise mediates the volume some what. I replaced the Pirelli tires with much quieter Michelins, because the first time I had it in for the noise they suggested new tires. No change in the howl, but a much nicer ride and much less tire noise.

The head troubleshooter for the dealer has ridden with me and hears the noise. They replaced the center bearing and the howl was still there. Next they replaced the rear differential and it still howls. We then took a ride in another 07 X3 they had there w/ 56k on the clock and guess what, it howled at 38 mph and 76 mph.

BMW have this now as a special case via the dealer and I have yet to hear of a solution.

Has anyone else had the howl? If you do, how was it resolved? I'd hate to think I paid as much as I did for a BMW and have it sound like the 53 Chevy pickup truck my buddy had in high school.