automotive transmission

automotive transmission

[¦ȯd·ə¦mōd·iv tranz′mish·ən]
(mechanical engineering)
A device for providing different gear or drive ratios between the engine and drive wheels of an automotive vehicle, a principal function being to enable the vehicle to accelerate from rest through a wide speed range while the engine operates within its most effective range.

Automotive transmission

The device in the power train of a motor vehicle that provides different gear ratios between the engine and drive wheels, as well as neutral and reverse. An internal combustion engine develops relatively low torque at low speed and maximum torque at only one speed, with the crankshaft always rotating in the same direction. To meet the tractive-power demand of the vehicle, the transmission converts the engine speed and torque into an output speed and torque in the selected direction for the final drive. This arrangement permits a smaller engine to provide acceptable performance and fuel economy while moving the vehicle from standstill to maximum speed. The transmission may be a separate unit as in front-engine rear-drive vehicles or may be combined with the drive axle to form a transaxle as in most front-drive vehicles. See Automobile, Automotive drive axle, Differential

The two general classifications are manual transmissions that the driver shifts by hand after disengaging the foot-operated clutch, and automatic transmissions that shift with no action by the driver. However, manual transmissions can have a clutch that is automatically disengaged by an actuator when the driver moves the shift lever, and automatic transmissions can have manual-shift capability which allows the driver to select the shift to the next lower or higher gear ratio by movement of the shift lever. See Clutch

The manual transmission is an assembly of gears, shafts, and related parts contained in a metal case or gearbox partially filled with lubricant. The transmission input shaft connects through the clutch and flywheel to the engine crankshaft (see illustration). The transmission output shaft connects through a driveshaft to the final-drive gearing in the drive axle. To get the vehicle into motion, reduction or underdrive gearing in the transmission allows the engine crankshaft to turn fast while the drive wheels turn much more slowly but with greatly increased torque. As the vehicle accelerates, and less torque and more speed are needed, the driver shifts the transmission into successively lower numerical gear ratios, known as higher gears. In a typical five-speed manual transmission, gear ratios are approximately 3.35:1 for first gear, 2:1 for second gear, 1.35:1 for third gear, 1:1 (direct drive) for fourth gear, and 0.75:1 (overdrive) for fifth gear. Most transmissions with four or more forward speeds are operated by a floor-mounted shift lever. See Gear

Six-speed manual transmission for a rear-drive carenlarge picture
Six-speed manual transmission for a rear-drive car

Automatic transmission provides automatic control of drive-away, gear-ratio selection, and gear shifting through four or five forward speeds. A typical automotive automatic transmission includes a hydrodynamic three-element torque converter with locking clutch, a planetary-gear system that provides overdrive in fourth or higher gear, and a hydraulic or electrohydraulic control system. Shifts are made without loss of tractive power. See Hydraulics, Torque converter

References in periodicals archive ?
According to the report, manual and automatic transmission systems are key segments of the automotive transmission market.
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Grede, Southfield, MI and Michigan Technological University, Houghton, MI, are the industry and research lead partners on the project, which will focus on reducing the amount of metal used in an automotive transmission differential case.
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In particular, it is developing cutting edge systems for the Automotive Transmission and Shifting Solutions and has created a sustainable ecosystem in cooperation with university research centres within a development program supported by the European Community.
a major automotive transmission system and parts manufacturer in Taiwan and OEM to automakers, recently announced start of mass production in September of high-end parts for Mercedes-Benz and BMW.
This process resulted expansion of technological base for manufacture of automotive transmission in the country.
78) Ethylene-co-vineyl acetate elastomer for automotive transmission and heavy duty sealing applications.
The actual nano roller is made of powdered metal--the same high tech metal used in automotive transmission gears--for unmatched resistance to wear.
Automotive transmission housings require a number of machining operations after the casting process, and a machining error at this stage of production is very costly.
Automotive transmission system company Torotrak published its pathfinder prospectus yesterday ahead of next month's expected pounds 400million flotation.
It features a six-speed manual transmission made in Muncie by Borg-Warner Automotive Transmission Division.

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