on my 1980 720 theres a half tube type deal that covers a long aprox 3/4inch screw that runs from the top of the frame to the bottom. its inside the backdoor on the right hand side. at the top of it theres a hex head that looks like you could turn with a socket or wrench. it looks like a long piece of heavy readyrod that is shielded behind this half tube thing. anyone have any clue what im talking about? iit runs basically to the bottom of the skidsteer skidplate at the back where it angles up.