Editing Automatic transmission (section)

====1904–1939: Predecessors to the hydraulic automatic====
The 1904 Sturtevant "horseless carriage gearbox" is often considered to be the first automatic transmission for motor vehicles.<ref>{{cite web |title=The American Automobile 1861-1929 Chapter 2 |url=http://www.earlyamericanautomobiles.com/americanautomobiles2.htm |website=www.earlyamericanautomobiles.com |access-date=1 November 2020 |archive-date=22 February 2020 |archive-url=https://web.archive.org/web/20200222192744/http://www.earlyamericanautomobiles.com/americanautomobiles2.htm |url-status=dead}}</ref><ref>{{cite web |title=The Pros and Cons of Automatic Transmissions |url=https://stevesimports.com/blog/the-pros-and-cons-of-automatic-transmissions/ |website=www.stevesimports.com |access-date=1 November 2020 |language=en |date=30 September 2019}}</ref> At higher engine speeds, high gear was engaged. As the vehicle slowed down and engine speed decreased, the gearbox would shift back to low. However, the transmission was prone to sudden failure, due to the transmission being unable to withstand forces from the abrupt gear changes.

The adoption of planetary gearsets was a significant advance towards the modern automatic transmission. One of the first transmissions to use this design was the manual transmission fitted to the 1901–1904 [[Wilson-Pilcher]] automobile.<ref name="Automotor">{{cite news |title=The Wilson-Pilcher Petrol Cars |work=The Automotor Journal |date=16 April 1904 |pages=463–468, also pp. 492–496, and pp. 519–521}}</ref> This transmission was built in the United Kingdom and used two epicyclic gears to provide four gear ratios. A foot clutch was used for standing starts, gear selection was using a hand lever, helical gears were used (to reduce noise) and the gears used a constant-mesh design. A planetary gearset was also used in the 1908 [[Ford Model T]], which was fitted with a two-speed manual transmission (without helical gears).

An early patent for the automatic transmission was granted to Canadian inventor Alfred Horner Munro of Regina in 1923.<ref>{{cite web |last1=Government of Canada |title=Canadian Patent Database |url=http://brevets-patents.ic.gc.ca/opic-cipo/cpd/eng/patent/235757/summary.html |website=www.brevets-patents.ic.gc.ca |access-date=22 November 2020 |language=en |date=15 June 2015}}</ref> Being a steam engineer, Munro designed his device to use [[compressed air]] rather than [[hydraulic fluid]], and so it lacked power and never found commercial application.<ref>{{cite web|last1=Warwick|first1=Alan|title=Who Invented the Automatic Gearbox|date=9 April 2013 |url=http://www.nwtgearboxes.co.uk/who-invented-the-automatic-gearbox|publisher=North West Transmissions|access-date=11 October 2014}}</ref>

In 1923, a patent was approved in the United States describing the operation of a transmission where the manual shifting of gears and manual operation of a clutch was eliminated. This patent was submitted by Henry R. Hoffman from Chicago and was titled: ''Automatic Gear Shift and Speed Control''. The patent described the workings of such a transmission as "...having a series of clutches disposed intermediate the engine shaft and the differential shaft and in which the clutches are arranged to selectively engage and drive the differential shaft dependent upon the speed at which the differential shaft rotates". However, it would be over a decade later until automatic transmissions were produced in significant quantities. In the meantime, several European and British manufacturers would use [[preselector gearbox]]es, a form of manual transmission which removed the reliance on the driver's skill to achieve smooth gear shifts.

The first automatic transmission using hydraulic fluid was developed in 1932 by two Brazilian engineers, José Braz Araripe and Fernando Lehly Lemos.<ref>{{Cite web|date=2019-08-30|title=Top 10 All-Time Auto Inventions|url=https://www.inventorsdigest.com/articles/top-10-all-time-auto-inventions/|access-date=2021-03-29|website=Inventors Digest|language=en-US}}</ref><ref name="hearst"/>

The evolution towards mass-produced automatic transmissions continued with the 1933–1935 [[REO Motor Car Company]] ''Self-Shifter'' semi-automatic transmission,<ref name="hagerty.com">{{cite web |title=6 of the worst automatic transmissions ever |url=https://www.hagerty.com/media/maintenance-and-tech/6-of-the-worst-automatic-transmissions-ever/ |website=www.hagerty.com |access-date=9 August 2020 |date=8 August 2019}}</ref> which automatically shifted between two forward gears in the "Forward" mode (or between two shorter gear ratios in the "Emergency low" mode). Driver involvement was still required during normal driving, since standing starts required the driver to use the clutch pedal.<ref>{{cite web|url=http://auto.howstuffworks.com/reo-cars1.htm|title=How Reo Cars Work|date=15 June 2007|access-date=24 October 2017}}</ref> This was followed in 1937 by the [[Oldsmobile]] ''Automatic Safety Transmission''. Similar in operation to the REO ''Self-Shifter'', the ''Automatic Safety Transmission'' shifted automatically between the two gear ratios available in the "Low" and "High" ranges and the clutch pedal was required for standing starts. It used a planetary gearset.<ref>{{cite web |title=The Oldsmobile automatic safety transmission operated by the short lever shown on the steering column |url=https://digitalcollections.nypl.org/items/510d47db-bb52-a3d9-e040-e00a18064a99 |website=www.nypl.org |access-date=9 August 2020 |language=en}}</ref><ref>{{cite web |title=No clutch to press! No gears to shift! |url=https://www.autonews.com/article/19970818/ANA/708180702/no-clutch-to-press-no-gears-to-shift |website=www.autonews.com |access-date=9 August 2020 |language=en |date=18 August 1997}}</ref><ref>{{cite web |title=How Oldsmobile Cars Work |url=https://auto.howstuffworks.com/oldsmobile-cars1.htm |website=www.howstuffworks.com |access-date=9 August 2020 |language=en |date=20 June 2007 |archive-date=20 September 2020 |archive-url=https://web.archive.org/web/20200920073229/https://auto.howstuffworks.com/oldsmobile-cars1.htm |url-status=dead}}</ref> The Chrysler ''[[Fluid Drive]]'', introduced in 1939, was an optional addition to manual transmissions where a fluid coupling (similar to a torque-convertor, but without the torque multiplication) was added, to avoid the need to operate a manual clutch.<ref>{{cite web |title=The Fluid Drive torque converter |url=https://www.allpar.com/mopar/fluidrive.html |website=www.allpar.com |access-date=3 November 2020}}</ref><ref>{{cite web |title=Video: An Introduction to Chrysler Fluid Drive |url=https://www.macsmotorcitygarage.com/video-an-introduction-to-chrysler-fluid-drive/ |website=www.macsmotorcitygarage.com |access-date=3 November 2020 |date=24 October 2017}}</ref>