I have a Kubota M8540 hydraulic shuttle. I have a problem with the shuttle shifting from reverse to foward. The tractor with shift fine when cold then after running about 30-45 minutes the it will start to not shift from reverse to forward. when it starts doing this it will be slow to shift from reverse to forward then as it gets hotter it will not move foward at all. But it will always go in reverse. It does not seem like the clutch because it will pull fine when it is going forward does not seem like it is slipping seems to me it would do it all the time hot or cold and it does not run hot. (I had a M9000 that the clutch went out on, and it would run the engine hot because of over running it when the clutch slipped) Fluid and hydraulic filters have been changed recently. Is this a shuttle valve problem? Can anyone help me with this?