Originally Posted by joes04bonneville
After I install the new passenger mount I will post the results.
Do you think the cradle mounts have anything to do with this?
They could, but its unlikely on a 2004. Check them out anyway.
A common problem I've seen is failure of the CV shaft/axles. If those have too much play, they will vibrate under higher speeds. The way to tell is to get on the highway when its vibrating, then let off the gas and coast. Pay attention to the vibration. Then accelerate hard. If between your coasting and acceleration the vibration changes, goes away, or gets heavier, then one or both of your CV shafts are bad.