Did you know automatic transmission was patented in the same year as insulin in 1923? It was also used in World War II M-5 Stuart tanks created by General Motors in 1942.
Advertised as the greatest advances in car since the self-starter in 1940s, the automatic transmission had a longer history than expected. You can find a Hydra-Matic Drive transmission, produced between 1939 and 1956, on display at the Ypsilanti Automotive Heritage Museum (see below).
Below is a history of automatic transmission collated in chronologically order from various sources, including the patent, on the Internet:-
- In 1921, the first automatic transmission was invented by a Canadian steam engineer, Alfred Horner Munro. Alfred Horner Munro ended up with the patent to back-up his claim, a Canadian patent in 1923 followed by similar in the UK (1924) and United States (1927). Munro designed his device to use compressed air rather than hydraulic fluid so it lacked power and never became sold commercially.
- In April of 1922, Earl Thompson, a young engineer, armed with drawings and data for a prototype synchromesh transmission, set out for Detroit to sell it to the automobile industry.
But the automobile manufacturers were not impressed; their customers were satisfied with manual transmissions as they were.
Thompson persisted. After several trips between Oregon and Detroit, and months spent improving the design, he had a better design patented.
- On 9 October 1923, the engineer Earl A. Thompson received his patent for his automatic gear shifting mechanism. https://patents.google.com/patent/US2101825
- In 1924, he finally met with Lawrence Fisher, managing director of Cadillac Motor Car Division under General Motors, and Ernest Seaholm, Cadillac's chief engineer. They were interested in the idea, and Thompson was retained as a consultant while the transmission was perfected. Cadillac also purchased Thompson’s patents.
- In 1928, with Thompson’s help offered a refined version of it as the Synchro-Mesh Transmission in 1928 Cadillacs. This invention was only the first step towards Thompson’s goal of designing a fully automated transmission.
- In May 1939, General Motors started production on the Hydra-Matic on the Oldsmobile cars. Oldsmobile was the first Automatic Transmission to be mass-produced and selected because of its economies of scale (Oldsmobile sold more cars than Cadillac and Buick at the time) and provided a test bed for its more expensive model (protecting the reputation of Cadillac and Buick in case of a market failure of the new transmission). This forever changed the automotive industry and was advertised as: “The greatest advance since the self-starter.”
- In October 1939, the first Oldsmobiles equipped were shipped. It was be sold as an $57 option in the 1940 Oldsmobile line.
- In 1941, the Hydra-Matic option rose to $100.00. It also became an option on Cadillacs for $125.00. Almost 200,000 had been sold by the time passenger car production was halted for wartime production
- In 1942 during World War II, the automotive plants stopped building cars so they could focus on building M-5 Stuart tanks and military vehicles for the war. These M-5 Stuart tanks were equipped with the Hydra-Matic Transmission.
- During the post-war time, the demand for vehicles with the Hydra-Matic was high. By this point, 3 out 4 General Motors cars sold came equipped with this option. The system was ‘battled hardened’ and the argument went that if it’s good enough or tanks in wars, it should be fine for a car on a road.
- In 1948, the first hydraulic transmission using torque converter was the Dynaflow, introduced by Buick. The Dynaflow only had two forward gears and reverse. Compared to the Hydra-Matic, the introduction of torque converter multiplying torque and power it made the 2-speed very powerful and efficient for its time. It was used with larger engines or racing cars, and the Hydra-Matic remained in cars with smaller engines.
- In 1949, Packard designed the 2-speed Ultramatic fully automatic transmission.
- In 1950, General Motors came up with the Power Glide. The Power Glide is still used today in top fuel and many quarter-mile racing cars as the king of automatic transmissions for racing with some mods. Borg Warner introduced the first automatic transmission with 3 speeds and the use of a lock-up torque converter.
- The Hydra-Matic went through continual upgrading and refinements through 1955, but the basic design and theory used were consistent throughout its remarkably long life span.
- By the mid-1950s, almost all major car companies including Bentley, Lincoln, Ford, and Studebaker purchased 3-speed automatic hydraulic transmissions from General Motors.
- In 1956, General Motors redesigned the Hydra-Matic with the Jetaway based around using two fluid couplings, to allow a "dual range" feature. This transmission was called the Controlled Coupling Hydra-Matic, or "Jetway" transmission. The original Hydra-Matic remained in production until the mid-1960s.
- In 1964, General Motors released a new transmission, the Turbo Hydramatic, a three-speed transmission that used a torque convertor. The Turbo Hydramatic was among the first to have the basic gear selections (Park, Reverse, Neutral, Drive, Low) which became the standard gear selection used for several decades.
- In 1969, the "Jet" quickly gave way to the Turbo Hydra-Matic. The original Hydra-Matic remained in production until the mid-1960s.
The invention by Earl Thompson certainly reached its potential with many of us forgetting how easy it is to switch gears nowadays. With inventions after that such as CVT, automatic transmission became more and more powerful for drivers on the road.