Mine is a MaxxAir MaxxFan, manual-opening, exhaust only. I forget the model number.
The only problem I had with mine is that the knob that raises and lowers the cover stripped out, so that it would turn and the cover wouldn't move. THAT rattled, until I got it fixed. Had to replace two parts at a cost of about $15, and problem fixed. To make sure the same thing doesn't happen to you, don't crank it down too tightly. I gave mine a right proper twist when I was gearing up for hurricane Isaac last year, thinking tighter is always better. Not so. Turns out I stripped out the worm gear on the inner end of the knob's shaft. It's only made of pot-metal, and strips out easily.
Anyway, thanks to the built-in rain hood, the cover only has to be barely finger-tight when closed, not cranked down hard, even when preparing for major storms. Wish I'd known thenů
Mine doesn't rattle anymore in any position, up down, or in-between. When stored (and I'm not expecting a hurricane) I keep it partially open to vent heat and/or control condensation. Camping, it's fully open and tunning at whatever speed seems most appropriate (with the AC on, it's open with the fan turned off). Driving down the road, it's usually fully closed to minimize road noise, but I have driven with it open a few times. Didn't rattle then, either; I just didn't like the sound the slipstream makes blowing around it.
Engineering: Finding complex solutions to simple problems you didn't even know you had.