User 7522

Hey I posted this in another place, but I wanted to post again to see if I'd get different opinons. I have a strange wind/whistling noise that starts when my car gets around 40mph. Its really hard to describe...it almost sounded like there was an a/c problem but I turned the ac off and it didnt help it. You can hear the sound everywhere but its strongest in the back. I was told to check the Differential Fluid, which I did today and had it flushed. The sound was a little better I think but I still hear it. Any other help?? Thanks so much!