Hey guys, I was just cruzin today and I noticed a bad thing that my SCrew did. I lowered my back two windows ONLY about 5-6 inches and it felt like the doors were gonna fly off the truck it started vibrating so bad. I thought something was wrong, so I turned off the radio and rolled up the windows and it was as smooth as can be. Roll the back two windows down 5-6 inches again and all hell breaks lose. I thought it might just be wind noise, so I did it again and I noticed that my fold down console (60/40 front seats) was shaking as well as the passenger seat. This was all done at 55-60 mph. Does this occur on all SCrews? Just thought I'd ask. Thanks guys. (and no I was not driving through a tornado )

 

It does that on SuperDuty Crew Cabs as well. I have rode in 3 SD CC, and all of them did that. It is really annoying. At one point it almost appeared as if the passenger seat was about to snap in half.

 

Just open the moonroof and there's a nice flow

 

I believe what your experiencing is known as a "Hemholz Resonator". The simplest explanation is the vibrating sound produced by blowing across the opening of a gallon jug (like they used to do on HE HAW). By opening another window (such as the moonroof or rear slider) you are allowing an airflow inside the cab, thus reducing the pressure differential between the air inside and the air outside. Actually the same (Bernouli's) principal that explains the damage a tornado produces is at work here. You might also try opening the dashboard vents, this could help reduce the "buffetting" of air at the rear windows.