Halderman: If a vibration is felt or seen in the dash, this usually indicates a fault with the front wheels or tires. Because these and everything in the front suspension has been checked, this leads me to think outside the box. I experienced a similar situation when test driving a customer's pickup truck. At lower speeds, everything was smooth, but when a certain speed was reached, the hood started to shake, and the dash and steering wheel began to shake, too. It turned out that the owner said that it was fine until he installed a bug shield on the front edge of the hood. To check to see if this was the cause, the bug shield was removed and the vibration problem did not occur. Therefore, check to see if there is an aftermarket bug shield or a covering over the front of the vehicle. If so, try removing it to verify that this is the cause.