Well this has been an eventful learning curve for me! Lets start with the obvious the three point must come off and be flipped over then the end plate that faces the shifter must be bumped back at least a half inch to get access to the snap ring holding the whole thing together. Once you have the snap ring out you will need a long board to gently knock the piston and retaining plate out towards the shifter. After these are out diagnosis is fairly straight forward the factory O ring will most likely be broken down and degraded to the point of distigration (look for pieces in the cylinder). Now the fun begins,the wide flat seal is still available from some tractor parts suppliers I got mine from Messicks close to home. You can find yours online or at your favorite farm supply store near you. You will also need an acceptable replacement for the round wide O ring that deteriorates thus passing pressure through to the return line to the hy trans reservoir. Mine blew out twice because I didn't understand the essence of the problem that the piston had high pressure blow by. I used two different O rings from Amazon suggested by a video on a 430 eagle hitch and they worked like a charm! Two of the skinny ones on the outsides of the ring groove and one fat one in the center. You will then need a piston ring compressor to bump the piston back into the cylinder. Replace the O ring on the retainer plate end with another of the skinny rings and reassemble the whole mess and you should be good as new!