I have some heavy bushhogging to do with my ford 4000 diesel. I intend on borrowing a friend's heavy duty bush hog to go over some land that was just clear-cut. It's a sho nuff heavy duty bush hog. I asked him what grade shear pin he used and he said "none". I asked him what protects the gearbox and he said "nothing". Well, I asked then what protects the tractor? He said if I hit something too big, the engine may shut off!! My tractor is a 1967 model and although it is strong, I don't want to hurt it. I have done a lot of hogging with lesser grade mowers over brush. opinions please