Standard gearboxes generally have two sets of gears: enter and output. the input & the output. The input gears are set to the countershaft, making them single units. It drives the person gears on the key shaft, which rotate freely around the bearings. Torque converter does a similar functionality https://gearbox70233.full-design.com/the-smart-trick-of-gearbox-that-no-one-is-discussing-76202353