I have a friend who broke his hip while riding his 2000 grizzly. His lower ball joint fell apart while traveling down a dirt rode at approximate. 35mph. It dug into the ground and flipped the quad head over heals resulting in his hip being broken. It appears the 2000 grizzly had a pressed in ball joint that came apart. Yamaha obviously new there was a problem because they redesigned the ball joint to a nut with cotter pin type in 2001. Did anyone have similar problems with theirs. My buddy is suing Yamaha.

 

This happens with all the quads....not just Yamahas.
It also happens on the newer ones you are talking about. Balljoints wear and break.....same thing happens with automobiles. I was driving an S-10 last year at 65mph when the right upper joint broke...SCAREY!!

I wish your buddy luck with his lawsuit, but I don't see him winning anything considering this quad is over 3 years old and the part that broke is a common replaced part on any quad regardless of brand and balljoint style.