LEGO TECHNIC AUTOMATIC TRANSMISSION | Lego Technic | Experimenting with a LEGO Technic Automatic 4-speed Transmission – How can this be improved? Created by Sariel https://bit.ly/3fU26gn | By Beyond the Brick | Facebook
LEGO MOC Lego Technic lockable automatic two speed gearbox [with free instructions] by SJ_LegoFan | Rebrickable - Build with LEGO
Lego Technic video about Lego 4 Speed Rotary Gearbox with build instructions