Automatic Transmission

Automatic Transmission

An automatic (also called automatic gearbox, or auto transmission) is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually. Most automatic transmissions have a defined set of gear ranges, often with a parking pawl feature that locks the output shaft of the transmission.

Similar but larger devices are also used for heavy-duty commercial and industrial vehicles and equipment. Some machines with limited speed ranges or fixed engine speeds, such as some forklifts and lawn mowers, only use a torque converter to provide a variable gearing of the engine to the wheels.

Besides automatics, there are also other types of automated transmissions such as a continuously variable transmission (CVT) and semi-automatic transmissions, that free the driver from having to shift gears manually, by using the transmission's computer to change gear, if for example the driver were redlining the engine. Despite superficial similarity to other transmissions, automatic transmissions differ significantly in internal operation and driver's feel from semi-automatics and CVTs. An automatic uses a torque converter instead of clutch to manage the connection between the transmission gearing and the engine. In contrast, a CVT uses a belt or other torque transmission scheme to allow an "infinite" number of gear ratios instead of a fixed number of gear ratios. A semi-automatic retains a clutch like a manual transmission, but controls the clutch through electrohydraulic means.

A conventional manual transmission is frequently the base equipment in a car, with the option being an automated transmission such as a conventional automatic, semi-automatic, or CVT. The ability to shift gears manually, often via paddle shifters, can also be found on certain automated transmissions (manumatics such as Tiptronic), semi-automatics (BMW SMG), and CVTs (such as Lineartronic).

The first automatic transmissions were developed by General Motors during the 1930s and introduced in the 1940 Oldsmobile as the "Hydra-Matic" transmission. They were incorporated into GM-built tanks during WW-II and, after the war, GM marketed them as being "battle-tested".

Read more about Automatic Transmission:  Comparison With Manual Transmission, Automatic Transmission Modes, Hydraulic Automatic Transmissions, Automatic Transmission Models, Continuously Variable Transmissions, Manually Controlled Automatic Transmissions

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... kW) DOHC 2.0-liter turbocharged "RS" with a 5-speed manual transmission only, followed by the "VZ" sedan and wagon and the "TZ" sedan and wagon with the 150 PS (110 kW) DOHC 2.0-liter ... The fuel efficiency for the 2.0-liter engine (non-turbo, manual transmission 4WD) is 10.8 km/L (31 mpg 25 mpg) based on Japanese Government emissions tests using 10 different modes of scenario standards ... available on the AWD equipped VZ wagon with an automatic transmission ...
Manually Controlled Automatic Transmissions
... Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral) ... Those controls take several forms Throttle kickdown Most automatic transmissions include some means of forcing a downshift into the lowest possible gear ratio if the throttle pedal is fully ... mechanically actuating a valve inside the transmission ...
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Borg-Warner 35 Transmission - Description
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