DC Gearbox TT Motor to LEGO® compatible Cross Axle : ID 3810 : $3.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Lego Gearbox with Reverse - Building Instruction | Doctor Engine's Blog
LEGO Technic 4 Speed Forward Transmission Gearbox -car truck NXT EV3 - new parts | eBay
RD711 – Gearbox 4 Speed Small 1 – Bouwstone.nl
This Remarkably Complex Lego 5-Speed Transmission Video Is A Great Way To Learn Transmission Basics - The Autopian
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
WIP] D-N-R-P + 4-Speed gearbox - LEGO Technic, Mindstorms, Model Team and Scale Modeling - Eurobricks Forums
Super Easy Building Instructions - 3 Speed Gearbox - 7 studs - Lego Technic | Lego gears, Lego, Lego technic
LEGO MOC 6-speed sequential gearbox by Whathetech | Rebrickable - Build with LEGO