My sunroof just scared me

I drive a 1991 Mazda Navajo. I've got the 4.0, 5-speed, 2-dr, with a sunroof. The sunroof is the kind that I can either raise the back up for a little air, or pop it out completely. Well, it's a nice day, so I wanted to pop it out. Now, I've only popped it out once before this - it took a lot of effort and I didn't want to break the glass, but now it comes out easy. It started to sprinkle a little, so I put my windows up. I slowed to turn into my road, and the truck started vibrating like hell to the point where I felt sick to my stomach. I assumed it was a flat tire, so I pulled right over. I walked around the truck a couple times, shook each tire, shook the truck, everything tight. I get back in and start driving, and sure enough, I hit 25mph and it's vibrating BAD. So, I stop, and look at the truck again. This time I really looked it over good. I even grabbed the wrench to see if the lugs were tight. Couldn't find a thing. So, I put my windows down, and take off slow, looking out the window at the tires. Nothing. I sped up and slowed down, problem gone. So, I put up my windows and stated to drive home - and it was back. I finally figured it out, with the windows closed, and the sunroof removed, the air over the top of the truck buffets in and out of the sunroof, like it's resonating or something. And when I say buffet, it feels and sounds like there is a dang helicopter in my truck! I can't hear the stereo over it, I start feeling motion sickness, and my hearing is foggy for a few minutes afterward. It only does it from 25mph to 40mph or so. At 55, there's just normal wind noise. Anyone else have a sunroof that does this?

if you open just the back windows in a honda pilot it does the same. haha. it drives your passengers nuts, its the difference in air pressure and the flow of air over your car

^^ same thing with rear windows on a cherekee.

Older watercooled VW Golfs did this. I had a 97 that actually shook it's headliner loose from the flex.
The structure is fine but the sheet metal skin doesn't take much to move it around.

A lot of vehicles will do it depending on wind conditions and postion of windows open. If you open a single window, either front or back the yaris my GF drives does it BAD! Now, crack the window kitty corner to it even an inch, and it goes away.