Vibration ONLY at 75 mph

Robbie2734 said

Let me take a shot at this, you said the pinion angle is -1 degree. I think the angle should be 3 to 4 degrees down. Maybe somebody could verify the numbers but I have a sense that this is your problem.

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I've ran the pinion all the way from down 5-degree's, to up 3-degree's moving in one degree increments and this had zero effect on the vibration. Please read initial post as I stated all of this when I started the thread. But I appreciate the insight.