Hi just got a 109 fixed head gasket and pto clutch. The problem is with the hydrostatic after running awhile hydro wants to load engine till it almost quits when you shut off the engine the tractor will not roll frontwards or backwards need some expert advice. If I rock the tractor the wheels will unlock and roll agin. I checked the checkvalves they are free. How ever the o-rings were flat is it possible they are bypassing when warm. I you can help please do Thanks Jim Im still trying to learn how to use this computer so bear with me.