Inadvertently exceeded driveshaft "Critical Speed" at Willow Springs.

This is why I'll repeat what I voiced in the rear gear poll,
I'm not fond of overdrives,I'd rather have an extra deeper
1st gear instead. Run a strong rear w/3.23's max, and
these vibration problems are minimized.The prop shaft
will have to handle more launch torque,but that's the least
of your worries on a road course.