These employed synchronizers to match equipment speeds, making it possible for for smoother shifts and easier driving. The mid-20th century saw the introduction of computerized transmissions.  Automatic gearboxes take away the need to get a clutch pedal, which disconnects the engine through the transmission so as to change gear.   https://automobile-gearbox52849.p2blogs.com/33049868/the-2-minute-rule-for-automobile-gearbox