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
Sariel.pl » Automatic 4-speed Transmission
LEGO MOC 4 Speed Automatic Transmission with Rotary Catch by Brick_Building_Data | Rebrickable - Build with LEGO