Lightly grease the power piston cylinder and o-rings and use two bolts to pull it until is seats. Then use the input shaft to center the gear teeth on the piston to the middle of its travel. The input shaft turns about 4.5 rotations so put it at 2.25 and you should be right about there. The flattend area on the input splines will be on the bottom if looking at the box in mounted position.