I'm not so fond of the 7000 series PTO.  I've never seen a 20-30-40-50 series give any trouble.  The 7000 reverted to the stupid shifter pin idea used in the 4010 and it had the same result.  The dry socket for the splined shaft isn't a very good idea either....never wore the splines off  the old ones. 

Never worked on the PTO on a 4430 in spite of putting 10000 hours or so on them, with over 8000 on one tractor.  The 7700 had the PTO messed up due to the poor design before it made 2500 hours.