[Velocity26]

I have a random noise that is speed related, not RPM, and comes and goes, and is driving me crazy.

The car is a 2010 automatic N54 with 60k miles.

It started a few months ago at about 35mph and continued up past 60mph. It sounds as if the right front tire has come apart and the belt is slapping the inside of the fender well. A passenger claims it sounds more like the center of the car, maybe the driveshaft tunnel.

I got home and checked all the tires, all are perfect, not the problem. Planned to get the car on a lift that weekend and the noise stopped. Several weeks later, starts again, lasts for a few days, then disappears.

Yesterday it started and was louder than ever. I was sure that, whatever it was, was going to come apart before I got home. Instead it simply stopped completely.

It sounds like a fast "fwap-fwap-fwap" that is loudest from 35-45mph, but can continue to 70 or 80 at times. No feeling sensation whatsoever, the car drives and handles perfect and nothing but speed seems to affect it.

Yesterday I put the car on a lift and removed the belly pan, exhaust, and all the heat shields. Everything looks perfect, like new. Nothing on the driveshaft, no marks on the undercarriage, heat shields, etc. Checked the guibo and it is perfect and looks like new. No cracks or even dry rubber. Checked the center bearing on the driveshaft and it also looks perfect, absolutely like new. The shaft is tight and there is not movement or slop. The universals look perfect too.

Any ideas? Anyone experienced anything like this before?

Thanks

[MysticRob]

If there's no accompanying vibration or anything it doesn't sound like a mechanical issue. I'd carefully look over all the trim pieces on the car. Bumpers, wheel well liners, covers, etc. Could be something affected by the wind at those speeds causing a harmonic vibration and flapping.

[Velocity26]

I checked all of the plastic panels in the fender wells and under the car. Everything is tight and all bolts are present.

It sounds totally tied to car speed, you can clearly hear the frequency of the slapping increase as you accelerate from say 35 to 45mph and it is almost a constant above 60 (when it continues that high). It does not vary with direction or straight/turn.

I can shift the car to neural and let the engine idle, the sound continues unchanged by RPM. I can rev the engine or change gears and the sound is constant.

I was 100% sure that I would find something wrapped around the driveshaft ... but there was nothing there, and no indication that there was ever anything there.

When it occurs, the sound is becoming louder, so it is likely a matter of time before
the cause surfaces ... I just hope it does not leave me stranded.

Thanks for your help!

[MysticRob]

Your description throws me off of thinking it's drivetrain, wheel bearing or anything suspension related. Definitely sounds speed related though.

Anything buried in the tires you've overlooked, like a screw, bolt, etc?

Maybe have someone drive their own car next to yours as you hear it and let them localize on each side at each end of the car as you go.

[tony55343]

Check the trim around the windshield/top of the windshield. This has not happened to me personally, but I have seen multiple threads on here describing the same noise etc, and it turned out to be the black trim that goes around the windshield was broken/damaged and flapping in the wind hitting the roof etc.