I have a 59' 641 I am in the process of going through. Here is a little back story. My Dad purchased the tractor a couple of months ago for the incredible expense of $250. The tractor had been sitting at the very least 5 years. I built the motor in it and thats when we found that the hydraulics didnt even try to work. I had him get the seal kit for it and we pulled it down. The fluid had a whole lot of water in it. Completely white. We drained, Cleaned and refilled the sump. All seals have been replaced and the piston resealed. We found the one seal missing between the piston and top plate. After reinstalling and priming the system we started it up. Immediately the lift goes all the way up, regardless of lift position. I should also mention we replaced the cam dowel pin. It had worn flat. I removed the plat and disconnected the control valve rod and removed it to make sure it was not staying engaged. reinstalled top plate, same thing. I removed again and used air to check and make sure the unloading valve is free and the check ball. Everything is free. New seals. But If i put air in the supply on the plate it immediately kicks up the arms no matter what. I was already leaning towards it being the draft control damaged in some way but I am just looking for some confirmations and maybe some advice on what to try. I removed the spring and everything off the draft rod on the outside of the top plate. Its not bent or broken so im not sure. Any help would be greatly appreciated.