I have a Super 55 S/N 35653-518, spec no. 15-0005 that I've been repairing/rehabbing.  When I first got it in March 2009 I split it and pulled the hydraulic unit.  I noticed at that time that the roll pin that is supposed to keep the PTO spline shafts together (located under the hydraulic unit towards the back) was broken allowing the PTO clutches to move forward and out of the drum.  I decided to just put a .25&quot; grade 5 bolt in it's place since at the time I thought with the splines that this should not take much abuse, It's only there to keep the two shafts from moving apart.  Well, I was wrong.  I used it to brushhog and everything worked great until the bolt decided to break (rather quickly actually).  Has anyone had this problem before?  Since then I found a roll pin to put back in, but don't want to go through this again if i can avoid it.  Thanks for any advice!