Combines I nee help

Henry, You mention a M2 below and now mention a M3. I am assuming that you have a Dyna-Power hydro in this machine. If I remember right there is a orfice fitting on servo control valve that has the small hydraulic hose hooked to it. I would remove small hyd. hose and remove fitting and clean well with brake cleaner and then blow air through fitting to make sure that it is clear. Also check small hyd. hose as it may be deteriorating inside and plugging orfice. The way you describe there must be something not allowing servo piston to move either way. Now if you have a late M3 with a Denison hydro I have seen a couple of things happen to servo control on those. One I had a piece of o-ring stuck in servo plate not allowing servo feed shoe slide across it.Also had a socket head screw that holds servo plate come loose and prevent servo control from moving. Hopefully you have the Dyna-Power as this unit is a little less involved in checking the items described. Hyper Harvest II

this is a puzzler to me. The valve is simply a rotary spool that alaigns orfices correctIJ They spin 360 degrees. I would leave in neutral, lock brakes or remove axle coupler for safety and try to move by hand and see if the spool kicks backIJ Servo must be stuck....for some reason as you say - it has to be hyd lock, but the spool simply cuts off oil. Unless the spool is broke and the pressure locks it up as it swellsIJ I would like to know the outcome on this one.