Vibration ONLY at 75 mph

Coyote Jack said

Is it possible that you have an air problem? That is, at 75 MPH the air traveling over/under/around the car is buffeting and setting up a vibration through the whole car. Try changing the stance of the car, raise or lower the front and see if the vibration changes or disappears. I'm just trying to think outside the box, because it looks like you have checked or changed most everything else.

Jack

Click to expand...

You might be on to something with that... A friend of mine that I work with formally did some pit crewing on a NASCAR winston cup car some years ago, and he came up with the same theory. And what semi-validates that is that with the car loaded with people in the back seat the vibration is slightly less noticable-ish... Probably the only time I notice a change is when the car is loaded and sitting lower in the back.

Great reply, and much appreciated! Will give this suggestion from you, and my friend a try.. If it is that, it would be very interesting, and frustrating as I really like the way the car sits right now. I can say though now even when the suspension was stock (prior to rebuild) the car did sit like exactly the same height, so hence the common denominator. Will post after I try changing the ride stance, in the mean time any other idea's?