Add the main spring and spring guide. The spring guide tabs slide into a hole in the gearbox. Once this has been done you will most likely need to hold down the parts wile going further.

Now take the other half of the gearbox and set it into place. Start at the front and work your way back. You may need push the spring guide down to get it into place.

If any of the axles to the gears or anti-reversal latch are out of place try using a small tool to push them into place.

If everything is looking right but the gearbox is still not coming together right try putting a tool down the air-nozzle and push the piston back to set it on it's track properly.

Now crack the back of the gearbox slightly so you can add the dust cover button.