I heard this same rattle when I tried out the demo NBC at my dealer. When I asked what caused it, they were unaware of anyone complaining. Well, I didnt like the color anyway so I ordered what I now own, which luckily, hasnt got the same rattles I do get some wind noise where the rear window engages the drivers front window. There is an air gap you can see through and Ive made an appt. with the dealer to adjust this. Other than my running boards seeping undercoating ooze their entire length, I'm a happy camper!!!!