10 Speed Sequential Gearbox with Park and Reverse - LEGO Technic, Mindstorms, Model Team and Scale Modeling - Eurobricks Forums
Lego Technic video about Lego 2 Speed Automatic gearbox - worm gear prototype. Includes build instructions.
Leic Power Functions Motor Set 113Pcs MOC Electric 6-Speed Synchronous Gearbox Assembly Kit with M Motor Compatible with Lego Technic : Amazon.co.uk: Toys & Games