Someone Made a Working Six-Speed Gearbox Out of Legos
RD711 – Gearbox 4 Speed Small 1 – Bouwstone.nl
LEGO MOC 4 speed gearbox - The best gearbox ever made by noggels | Rebrickable - Build with LEGO
Super Easy Building Instructions - 4 Speed Gearbox - Lego Technic | Lego mindstorms, Lego gears, Lego technic
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