The invention of the automatic gear change was the result of the combined efforts of several inventors, with notable contributions from Alfred Horner Munro and Adolphus Broomhall. Automatic gearboxes were first introduced in luxury vehicles in 1940, and eventually became available for mass-market cars in 1950. The first experimental hydromechanical transmission was developed in 1904 by the American engineer, Alfred Horner Munro. The transmission used a clutch centrifugal to control gear shifting and was based on a planetary gearbox. This prototype allowed for automatic shifts between two main gears and was operated by centrifugal weights that moved according to engine speed. In the 1930s, soviet engineers began developing new fluid-based transmissions as an alternative to manual transmissions, which were becoming increasingly unreliable due to high levels of mechanical wear and tear. As a result, they invented the world’s first automatic transmission using hydraulic pumps and valves as well as planetary gearsets for their transmission solutions. This groundbreaking invention offered superior performance compared to manual transmissions at the time and went on to become the foundation of today’s modern automatic transmissions.

The first automatic transmission prototype was developed in the early 1900s, soon after the invention of the internal combustion engine. It was a two-speed transmission with a forward speed and reverse gear and no clutch pedal, allowing drivers to change gears without having to manually disengage the clutch. The first fully automatic transmission system was developed in 1939 and used on General Motors’ Hydramatic cars, allowing for smoother acceleration and more efficient use of fuel than manual transmissions. This system had three forward speeds plus reverse, as well as an auxiliary drive that allowed it to be used on early engines that lacked processing capacity.

In 1932, the Canadian steam engineer Alfred Horner Munro was granted a patent for the first automatic transmission. The "Munro Patent" was an improvement on earlier designs that lacked power and efficiency. Munro's invention allowed for smoother gear changes than ever before with compressed air or hydraulic power as its energy source. Munro's design used four forward gears and one reverse gear with a single shift lever, allowing drivers to change gears without using a clutch pedal. The design also featured a two-speed planetary gear system which enabled it to shift smoothly between low speeds and high speeds. As well as this, he added brakes to control slippage between the drive wheels during shifts which further improved reliability and performance of the vehicle transmission system.

Another automatic transmission was created in 1921 by Oldsmobile, a division of General Motors. This new transmission was called the “Oldsmobile Economies” and it offered drivers a choice between two gears: forward or reverse. This new transmission allowed for smooth shifting between gears and the ability to start from a full stop without the need for manually engaging the clutch. Although American cars were the first to feature automatic transmissions, Soviet cars soon followed suit with their own version called the “Volga Model” in 1935. This model featured an automatic three-speed gearbox as well as manual operation, allowing drivers to switch between manual and automatic modes depending on their preference at any given time. The Volga Model proved popular among Soviet drivers and went on to be used in many other soviet-built vehicles over the years.

However, it was General Motors who first created the modern automatic transmission in 1939. This model was called the original Hydra-Matic and became the prototype for all subsequent autoshifters. The Hydra-Matic worked on a four-speed planetary gear set with two clutch packs to shift gears automatically. The first synchro transmission from General Motors was released in 1940 and GM marketed it as the GM Hydramatic, which had commercial success. As technology progressed, a new type of automatic transmission called a mesh gearbox started to emerge in the 1950s and it quickly gained popularity due to its ease of operation. The booming post war economy also meant that more people had access to vehicles with automatic transmissions, leading to their increased usage around the world.

However, who is granted the credits to be the inventor of automatic transmissions? On the one hand invention of the automatic transmission is largely attributed to Alfred Horner Munro. In 1921, he developed a speed preselector transmission which could shift gears without the help of a clutch pedal. This was followed by the development of Reo motor's 1923 “safety transmission”, which shifted into an appropriate gear ratio automatically according to vehicle speed. This laid down the foundations for modern day automatic transmissions. Subsequently, in 1932 General Motors introduced their “preselector” transmissions which used electro-mechanical controls to select an appropriate gear ratio based on engine speeds and road conditions. These models also featured a safety system that prevented drivers from selecting an inappropriate gear ratio for their current speed levels. Today, all modern cars come equipped with automatic transmissions that offer smoother shifting between gears and improved fuel efficiency due to optimized gear ratios and transmission output control systems.