So as the title says, I have a vibration at 45 MPH. I have a 07 CC 4x4 Big Tow. I have replaced the tires, new bilstiens all the way around and a rough country 3 inch lift. I did all these after purchasing the truck. The vibration has always been there, but has gotten worse. I shift out if overdrive to 4 and it diminishes enough that you think it's gone. But on occasion, you can still feel it. If you shift to 3 its completely gone. In overdrive, if you speed up it goes away if you slow down it goes away.... I'm stumped and thinking it's the trans.... Any ideas?