The other day I was moving a disable lawnmower in my yard. As I started to try to move the old mower the mower wouldn't pull it. It started to move the motion lever forward when the trans got very noisy to the point where I could feel the vibrations in the motion lever. Now I live on a hill I have no problem mowing. I can plow my garden even. But it seems to make an excessive amount of "transmission noise". It's the same sound it normally makes only much louder to the point that you can feel the pump working but it wont pull. Is there a bypass valve? I have a 71 12 hp massey fergusson that will pull more than my craftsman. Any Ideas??