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Cutaway view of a 2007 Toyota AA80E hydraulic automatic Typical gear selector for an automatic transmission. An automatic transmission (sometimes abbreviated AT) is a multi-speed transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. The 1904 Sturtevant ...
Automatic transmission fluid. Automatic transmission fluid (ATF) is a hydraulic fluid that is essential for the proper functioning of vehicles equipped with automatic transmissions. Usually, it is coloured red or green to differentiate it from motor oil and other fluids in the vehicle. This fluid is designed to meet the unique demands of an ...
A transmission (also called a gearbox) is a mechanical device which uses a gear set—two or more gears working together—to change the speed, direction of rotation, or torque multiplication/reduction in a machine. [1] [2] Transmissions can have a single fixed-gear ratio, multiple distinct gear ratios, or continuously variable ratios. Variable ...
A direct-shift gearbox (DSG, German: Direktschaltgetriebe [1]) [2] [3] is an electronically controlled, dual-clutch, [2] multiple-shaft, automatic gearbox, in either a transaxle or traditional transmission layout (depending on engine/drive configuration), with automated clutch operation, and with fully-automatic [2] or semi-manual gear selection.
Older automatic transmission designs only use a single line pressure control solenoid which modifies pressure across the entire transmission. Newer automatic transmission designs often use many pressure control solenoids, and sometimes allow the shift solenoids themselves to provide precise pressure control during shifts by ramping the solenoid ...
The operating speed of the engine and wheels are also different and must be matched by the correct gear ratio. As the vehicle speed changes, the ideal engine speed must remain approximately constant for efficient operation and so this gearbox ratio must also be changed, either manually, automatically or by an automatic continuous variation.
The precise definition varies by location. Compare gross vehicle weight. [1] keyless entry kickdown. Also forced downshift. A system that enables a driver to select a lower gear than the one automatically engaged by an automatic transmission, e.g. when accelerating rapidly, usually by depressing the accelerator pedal fully. [1] kingpin
The viscometrics for gear oils are standardized in SAE J306. Multigrade gear oils are becoming more common; while gear oil does not reach the temperatures of motor oil, it does warm up appreciably as the car is driven, due mostly to shear friction (with a small amount of heat conduction through the bellhousing from the engine block).