LEGO MOC 2 Speed Gearbox by thatbrickguy | Rebrickable - Build with LEGO
The greatest gearbox
Amazon.com: LEGO Technic COMPLETE GEARBOX ASSEMBLY 2 x 4 x 3 1/3 Trans-Clear Wormbox gear motor REDUCER block Mindstorms robotics ev3 NXT transparent robot building power functions part 6588
How to Make an Easy Customisable Lego Transmission Part 1 : 4 Steps - Instructables
Shifting Gears | The Lego Car Blog
How to make a gearbox in LEGO technic (5 Speed+Reverse) - YouTube