PG 38 of the mower manual has the solution. Basically there are two holes in a support bracket one the upper is fro keeping the mower deck in the up position and allowing the three point hitch to operate normally. There is an lock up clevis pen that goes through the hole that is retained with a hairpin cotter. It may be a little tuff to do as it is close to the back tires. I am not sure if you need the deck in the up position while changing the clevis pin position or not. I am assuming the deck needs to be in the raised position, but will not know to later next week when my next day off occurs. I have a picture but can't figure out how to copy and paste into this forum,.