I have new problem with my 2003 A4. At speed above 55 mph the car develops a sound similar to a flopping flag in a strong wind. I checked the tires they look fine, I did find that the belly pan was ripped so I replaced with a new one thinking that this maybe a cause of the problem. However the problem did not go away. Any thoughts what this could be? It occurs even if the car is out of gear.

I greatly appreciate any feedback.

 

It sounds like a flopping flag? Thats a strange one, maybe check to see if you front and rear bumper is secure. Ever see those crappy honda civics with body kits that flap around in the wind? I would grab a hold of those and make sure they are tight. If they are its more than likely your tires.