Vooo, vooo sound from QX4, not sure if its tire noise

[ulenie]

My 2001 QX4 makes this sound that is hard to describe when going over 30mph. At first I thought it was tire noise but a couple of other people riding with me also asked me what the noise is. Its coming from underneath the car and starts at about 30 miles per hour and seems to dissipate at high way speeds. Not sure if it can be described as a whine. Its some kind of rotational sound hence my vooo, vooo description. I recently had the drive shaft slip yolk lubed up to fix a bang sound: 2001-qx4-feels-like-cabin-is-loosely-co ... 83514.html

So now am going to tackle this noise. I need some guidance on how to diagnose, if its tire noise or something else. Drive shaft bearings may be?

[Buzzman]

Had a similar problem a few years ago. Turned out to be a bad u-joint (the one at the rear, at the differential).
Replaced it and all has been good.

[Towncivilian]

Is it a whistling noise? Mine whistles between 30-40 miles an hour or thereabouts. I'm almost certain it's from the rear air vents that are used to equalize pressure of the cabin when you close a door.

[ClintSmith]

Mine does this as well. Sounds kind of like a deathly ill owl living in my drivers front wheelwell. It's ONLY if it in negative 2 degrees. (yes Fahrenheit lol, minnesota winters suck.) and only if when I have parked with it in awd, or put it in awd. (It's below minus 2, i'm not going that fast in this cold and everything is frozen so it's a basic necessity) I was thinking that it could be my fluids freezing, because once I drive a few blocks it dissipates. Have you tried covering your vents and going for a test drive Town? Liberal application of duct tape over the vent and all? :-P