9SLIDE the winch drum back onto the gearbox end-plate, ensuring it seats firmly onto the input shaft for the gears and the outer planetary gear itself. There should be a smear of fresh grease in the plastic bush the drum rides in, and in the outer seal as well.
Re-install the three crossbars onto the gearbox end-plate and ensure you use anti-seize, as the dissimilar metals can cause corrosion and lock bolts. Do the same again with the motor end-plate. With the winch assembled and the drum correctly aligned, re-install the motor onto the end-plate by either re-using the existing gaskets or replacing with silicone or new items. It can be difficult lining the long bolts up with their threads, so try having the motor 2-3mm away from the housing so you can see inside.