I have a 2000, 528i and when I am on the freeway I hear a faint whistle coming from the car. It happens all the time but only when I am stepping on the gas to maintain my speed, usually at around 70-90, when I let go of the gas it stops and when I floor it, it stops so it’s only whistling when im just trying to maintain my speed. It's not very loud but pertty noticeable, anyone have any clue as to what it could be? Any help or comments are welcome, thanks.

I have the EXACT same thing, and I know that my pinion bearing (in the differential) is going bad. So that may be it.

Yea, I have a 92 325is and I have the same whistling noise. Is it that serious???

Maybe the intake resonating or something

check your side mirrors sometimes the wind catches them just right and it makes a whistling sound. unless the whistling sounds like it is coming from teh engine compartment.

check your side mirrors sometimes the wind catches them just right and it makes a whistling sound. unless the whistling sounds like it is coming from teh engine compartment.

That's where my whistling sound comes from. Damn mirrors.. :mad