Vanpeltsales site go to clutch chatter.
http://www.vanpeltsales.com/FH_web/f...oubleshoot.htm
I had a multiple problems with mine. wrong washer holding the universal joint tight to the tranny tailshaft. It caused the bolt to loosen up and the U-joint would smash against the bearing retainer.
Worn c-clips in the tranny.
Oil on the clutch.