Editing Manual transmission (section)

=== 1890s to 1940s ===
[[File: PSM V57 D608 Cherrier two speed gear.png|thumb|right|Cherrier two speed gear, circa 1900<ref>[[Wikisource:Popular Science Monthly/Volume 57/August 1900/The Evolution and Present Status of the Automobile]]</ref>]]

Many of the first automobiles were rear-engined, with a simple belt-drive functioning as a single-speed transmission. The 1891 [[Panhard#Early years|Panhard et Levassor]] is considered a significant advance in automotive transmissions since it used a three-speed manual transmission.<ref>{{cite web |title=The 1891 Panhard et Levassor |url=https://www.themotormuseuminminiature.co.uk/1891-panhard.php |website=www.themotormuseuminminiature.co.uk |access-date=2 July 2020}}</ref><ref>{{cite web |title=Sliding Gearbox - 1891 Panhard et Levassor |url=https://www.youtube.com/watch?v=VkrjueYVvYA | archive-url=https://ghostarchive.org/varchive/youtube/20211030/VkrjueYVvYA| archive-date=2021-10-30|website=www.youtube.com |access-date=2 July 2020}}{{cbignore}}</ref> This transmission, along with many similar designs that it inspired, was a [[non-synchronous transmission|non-synchronous]] (also called ''sliding-mesh'') design where gear changes involved sliding the gears along their shafts so that the desired cogs became meshed. The driver was therefore required to use careful timing and [[throttle]] manipulation when shifting, so the gears would be spinning at roughly the same speed when engaged; otherwise, the teeth would refuse to mesh. This was difficult to achieve, so gear changes were often accompanied by grinding or crunching sounds, resulting in the gearboxes being nicknamed "crash boxes".<ref>{{cite web |title=1902 Panhard and Levassor |url=https://auto.howstuffworks.com/1902-panhard-and-levassor1.htm |website=www.howstuffworks.com |access-date=2 July 2020 |language=en |date=7 December 2007 |archive-date=4 July 2020 |archive-url=https://web.archive.org/web/20200704154635/https://auto.howstuffworks.com/1902-panhard-and-levassor1.htm |url-status=dead }}</ref> Even after passenger cars had switched to synchronous transmissions (i.e. with synchronizers), many transmissions for heavy trucks, motorcycles and racing cars remained non-synchronous, in order to withstand the forces required or provide a faster [[shift time]].