I've been told by Mark Williams and PST, that an aluminum 3 1/2" driveshaft would save at least 7-8 pounds over the 52 1/8" inch length, 3.5" chromoly Dynotech driveshaft I have currently. I've tried to contact Dynotech for a month now, but no success. My main goal is to improve a bad high speed vibration problem (75 -110 mph) which I believe is mainly due to the driveshaft being about 1 inch too short. Pinion angle has been checked and corrected to 2 degrees. New radial tires on aluminum wheels all around. I can push the driveshaft yoke into the 727 tail shaft about 1 3/4". Cass (Dr. Diff) and Mark Williams recommend having only 3/4" travel for the slip yoke. I though if I have to get a new driveshaft, maybe try an aluminum one instead of chromoly.

Any one ever had this type of high speed driveshaft vibration due to the driveshaft being too short? Did a correct length driveshaft fix the vibration issue?