My tractor just all the sudden wouldn't stop had no neutral and forward was jerky. Especially at a idle. Affected power steering as well. Loader and 3 pt hitch all worked normal. Let tractor cool, I had neutral and reverse back but forward was still jerky. I came and looked at some threads about the proportioning valves. At first I pulled them out and cleaned them real good carb choke cleaner and compressed air.. reinstalled them but opposite of where I took them out from. All worked well. Thought maybe reverse would then be jerky but all was good. Made sure to get tractor up to operating temp. As maybe the problem was worse as the oil heated up but everything checked to be working great. I ended up ordering new proportioning valves and installed them. Every thing is good to go. Now what caused this problem I have no idea. But seems like they will fail as I have read on other posts. Hopefully this help someone in the future.
