Well, I was traveling on I 70 last year in Western Kansas enroute to Colorado. My roadster glass window was also vibrating quite a bit and, at times, sounded like a bass drum at 65-70. But, out here, there are very strong crosswinds and I attributed it to that because I've driven 70 at other times and it hasn't made that sound. And, yes, my windows were up with the air on. If you get a 30-40 mph crosswind, I think it's going to vibrate the glass or plastic. If it were me, I probably wouldn't change unless it becomes more and more of a problem.