New to tractors and lots of issues with an old 851. My 3pt hitch only raises a few inches under load, but will come up slowly with nothing attached. I can make it raise a load fully by firmly pushing the draft control selector down or pulling it up and holding it. However, the selector lever only moves from horizontal to about 45 degrees upward...it does not go in the vertical down, draft postion. I have the manual and read many posts, but don not get why putting pressure on the draft control lever allows it to lift? To date, I have only replaced the hydraulic fluid and bled the system (no bubbles, good flow). Any advice before I pull the cover?