Editing Semi-automatic transmission (section)

=== 1930s–1940s ===
Prior to the arrival of the first mass-produced hydraulic automatic transmission (the [[General Motors]] [[Hydramatic|Hydra-Matic]]) in 1940, several American manufacturers offered various devices to reduce the amount of clutch or shifting input required.<ref>{{cite web|url= https://www.caranddriver.com/research/a31862769/how-does-an-automatic-transmission-work/ |title = How Does an Automatic Transmission Work?|date = 13 April 2020}}</ref> These devices were intended to reduce the difficulty of operating the [[Non-synchronous transmission|unsynchronised manual transmissions]], or "crash gearboxes", that were commonly used, especially in stop-start driving.

An early step towards automated transmissions was the 1933–1935 [[REO Motor Car Company|REO]] Self-Shifter,<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=hagerty.com |access-date=9 August 2020 |date=8 August 2019}}</ref><ref>{{cite web|url= https://www.autoindustriya.com/features/making-automatic-sense.html |title = Making Automatic Sense – Feature Stories|date = 29 September 2010}}</ref><ref>{{cite web|url= https://www.caranddriver.com/research/a31884931/what-is-an-automatic-car/ |title = What is an Automatic Car?|date = 13 April 2020}}</ref><ref>{{cite web|url=https://www.caranddriver.com/research/a31862769/how-does-an-automatic-transmission-work/ |title = How Does an Automatic Transmission Work?|date = 13 April 2020}}</ref> which automatically shifted between two forward gears in the "forward" mode (or between two shorter gear ratios in the "emergency low" mode). Standing starts required the driver to use the clutch pedal. The Self-Shifter first appeared in May 1933 and was offered as standard on the Royale and as an option on the Flying Cloud S-4.<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>

In 1937, the four-speed [[Oldsmobile]] Automatic Safety Transmission was introduced on the [[Oldsmobile Six]] and Oldsmobile Eight models.<ref name="hagerty.com"/> It used a planetary gearset with a clutch pedal for starting from a standstill and switching between the "low" and "high" ranges.<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=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=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=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 Automatic Safety Transmission was replaced by the fully-automatic Hydra-Matic for the 1940 model year.<ref>{{cite web|url= https://quality-coaches.com/transmission-repair/the-evolution-of-the-auto-transmission/|title=The Evolution of the Auto Transmission |website=quality-coaches.com }}</ref><ref>{{cite web|url= https://driving.ca/chevrolet/corvette/auto-news/news/hail-hydra-matic-the-rise-of-the-automatic-transmission |title=Shifting Times: The rise of the automatic transmission|date=6 January 2015}}</ref>

The 1938–1939 [[Buick Special]] was available with another Self-Shifter 4-speed semi-automatic transmission,<ref>{{cite web |title=How Buick Works |url= https://auto.howstuffworks.com/buick.htm |website=howstuffworks.com |access-date=8 August 2020 |language=en |date=5 June 2007}}</ref><ref>{{Cite web |title=1938-Buick-Folder.pdf |url=https://www.xr793.com/wp-content/uploads/2018/10/1938-Buick-Folder.pdf |access-date=16 October 2023 |website=xr793.com}}</ref><ref>{{cite web|url= https://ateupwithmotor.com/terms-technology-definitions/hydramatic-history-part-1/2/|title=Hydra-Matic History: GM's First Automatic Transmission |website=ateupwithmotor.com |date=29 May 2010}}</ref> which used a manual clutch for starting from standstill and an automated clutch for gear changes.

The 1941 [[Chrysler]] [[Vacamatic|M4 Vacamatic]] transmission was a two-speed manual transmission with an integral underdrive unit, a traditional manual clutch, and a fluid coupling between the engine and the clutch.<ref>{{cite web |title=The M6 automatic transmission |url= https://www.allpar.com/mopar/m6.html |website=allpar.com |access-date=9 August 2020}}</ref><ref>{{cite web |title=Chrysler transmissions-Vacamatic semi-automatic |url= http://www.gottransmissions.com/blog/chrysler-transmissions/chrysler-transmissionsvacamatic-semi-automatic |website=gottransmissions.com |access-date=9 August 2020}}</ref><ref>{{cite web |title=How Chrysler Works |url=https://auto.howstuffworks.com/chrysler.htm |website=howstuffworks.com |access-date=9 August 2020 |language=en |date=1 June 2007}}</ref> The two-speed transmission had "high" and "low" ranges, and the clutch was used when the driver wanted to switch between ranges. For normal driving, the driver would press the clutch, select the High range, and then release the clutch. Once the accelerator was pressed, the fluid coupling would engage and the car would begin moving forward, with the underdrive unit engaged to provide a lower gear ratio. At between {{convert|15|and|20|mph|km/h|abbr=on}}, the driver would lift off the accelerator and the underdrive unit would disengage. The Vacamatic was replaced by a similar [[Presto-Matic|M6 Presto-Matic]] transmission for the 1946 model year.

Similar designs were used for the 1941–1950 [[Hudson Motor Car Company|Hudson]] Drive-Master<ref>{{cite web |title=1941–1947 Hudson |url=https://auto.howstuffworks.com/1941-1947-hudson3.htm |website=howstuffworks.com |access-date=8 August 2020 |language=en |date=16 September 2007 |archive-date=20 August 2008 |archive-url=https://web.archive.org/web/20080820183959/http://auto.howstuffworks.com/1941-1947-hudson3.htm |url-status=dead }}</ref><ref>{{cite web |title=Step-Down: The 1948–1954 Hudsons |url= https://ateupwithmotor.com/model-histories/step-down-hudsons/ |website=ateupwithmotor.com |access-date=8 August 2020 |date=6 September 2009}}</ref> and the ill-fated 1942 [[Lincoln Motor Company|Lincoln]] Liquimatic.<ref>{{cite web |title=Automatic Failure: Ford's 1942 Liquamatic Experiment |url=https://www.macsmotorcitygarage.com/automatic-failure-fords-1942-liquamatic-experiment/ |website=macsmotorcitygarage.com |access-date=8 August 2020 |date=7 February 2017}}</ref><ref>{{cite web |title=Automotive History: Lincoln's Liquamatic Drive – Failure to Upshift |url= https://www.curbsideclassic.com/automotive-histories/automotive-history-lincolns-liquamatic-drive-failure-to-upshift/ |website=curbsideclassic.com |date=30 May 2019 |access-date=8 August 2020}}</ref> Both of these combined a 3-speed [[manual transmission]] with automated shifting between the 2nd and 3rd gears, instead of the Vacamatic's "underdrive" unit.

The Packard Electro-Matic, introduced in the 1941 [[Packard Clipper]] and [[Packard 180]], was an early clutchless manual transmission that used a traditional friction clutch with automatic vacuum operation, which was controlled by the position of the accelerator.