you have to do the adjustment with the manifold cool, and do it from underneath. You have to back the screw out (counter-clockwise looking from top) to tightenit up. Jack it up and put on stands. Then try turning the wheel 1/2 turn each way after each 1/2 turn of adjustment. You may not be able to get all the play out without the gears binding. SOL in that case live with it or rebuild the box(+/-$500)