Never really built a gearbox before but knew the basics of a 2 and 4 speed boxes so i smashed them together and build this kinda small 8 speed gearbox : r/legotechnic
WIP] D-N-R-P + 4-Speed gearbox - LEGO Technic, Mindstorms, Model Team and Scale Modeling - Eurobricks Forums
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