It's just fine. No excessive wind noise and I was doing 75 mph on that trip (150 miles round trip - about 24 mpg on it). I've used this box for five years and love it. I do have a mat on the bottom as I was worried about rattles, but never had any. Could be due to the mat or not, but it's pretty quiet.Have you driven on the freeway with it? How is it on the QX? Is it noisy/lifting/rattling? Or does it work well?