A handbook transmission requires the motive force to manually decide on the gears[6] by working a gear stick and clutch (which will likely be a foot pedal for vehicles or possibly a hand lever for motorcycles). Torque converter does a similar purpose that the clutch does from the manual https://louiszzwxx.madmouseblog.com/14280396/the-fact-about-gearbox-that-no-one-is-suggesting