Modifying DG01D-E-sparkfun motor

Hello,

I am using these motors with the XRP platform. My competition rules are very loose to promote unique ideas and mine is to create a gear locker to lock the two shaft gears together to cut my reduction ratio in half. Im looking for help getting the dimensions of the gears inside the motor so I can 3d print a reliable and suitable piece for my project. Any help is greatly appreciated.