Thanks to all who post problems and the answers with solutions to those problems here.
I have a 62 4000 and the PTO kept disengaging when mowing. I searched the archives and got the information that most likely, the problem was with a snap ring on the PTO in the rear (seeing as I had a bit of play on the PTO shaft). Well, I ordered all the parts for the project (bearings, seals, snap rings, & etc. -- complete overhaul) thinking that this is the problem and what do you know, it was!
However, there was also one other problem with the PTO -- not only was the large snap ring busted, but so was the PTO cover. This is the item that the PTO goes through at the back end of the tractor -- the large snap ring fits in a channel on this piece. It seems as if someone did not pay attention to the distance between the PTO shaft + shaft on the implement to ensure that there was enough play in the system. The implement shaft pushed into the PTO causing the cover to break at the snap ring.
Hope this helps someone else out there as previous posts have helped me.
P.S. I would order the same way next time -- the cover may or may not be broken -- no sense spending the ~140 to buy the new cover unless absolutely needed!