rotational noise

[Thom]

Ok so, I have a ratational noise coming from the front end. It sounds like the tires are half flat. It only makes the sound when I am driving. I shifted to N and still makes the noise. About 2000 miles ago I had the front axles done. I know its a tough question to diagnose on the site but... what about the front diff ? would I get that sort of noise if the fluid was low ?
Any suggestions would help. New brakes also done 2mths ago. I touched the rotors etc...cool, not hot.
Thanks.
Tom

[Thom]

Sorry...update...its a 2002 X5 3.0l with 146000 kms.