Originally Posted by 5.7stroker

Bump it.

I'm getting a vibration which seems to only occur at 65-75mph also, then when you increase speed it goes away. Natural resonance of the rear suspension? My pinion angle is at 2 deg, so I'm wondering if that is what is causing it. My 2nd guess would be a wheel imbalance, or bent rim.

Originally Posted by wssix99

Vibrations that come and go at those speeds are generally at the wheel and are a classic indicator of imbalance. I'd start with checking the wheel balance and then work back from there, focusing on unsprung components first.