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120-420: Early automobiles used sliding-mesh manual transmissions with up to three forward gear ratios. Since the 1950s, constant-mesh manual transmissions have become increasingly commonplace, and the number of forward ratios has increased to 5-speed and 6-speed manual transmissions for current vehicles. The alternative to a manual transmission is an automatic transmission . Common types of automatic transmissions are

240-429: A clutchless manual , is a type of multi-speed automobile transmission system that is closely based on the mechanical design of a conventional manual transmission , and automates either the clutch system, the gear shifting, or both simultaneously, requiring partial, or no driver input or involvement. Earlier versions of these transmissions that are semi-automatic in operation, such as Autostick , control only

360-411: A countershaft (also called a layshaft ) and an output shaft . The input shaft is connected to the engine and spins at engine speed whenever the clutch is engaged. The countershaft has gears of various sizes, which are permanently meshed with the corresponding gear on the input shaft. The gears on the output shaft are also permanently meshed with a corresponding gear on the countershaft; however,

480-424: A clutch to manage the linkage between the engine and the transmission, and decouple the transmission from the engine during gearshifts and when the vehicle is stationary. Without a clutch, the engine would stall any time the vehicle stopped, and changing gears would be difficult (deselecting a gear while the transmission requires the driver to adjust the throttle so that the transmission is not under load, and selecting

600-675: A column shifter and more practical, as the gearbox was mounted in front of the engine. The linkage for the shifter could then be positioned on top of the engine. The disadvantage is that shifting is less comfortable and usually slower to operate. Newer small cars and MPVs , like the Suzuki MR Wagon , the Fiat Multipla , the Toyota Matrix , the Pontiac Vibe , the Chrysler RT platform cars,

720-417: A column shifter are the ability to switch between the two most commonly used gears—second and third—without letting go of the steering wheel, and the lack of interference with passenger seating space in vehicles equipped with a bench seat . Some smaller cars in the 1950s and 1960s, such as Citroën 2CV , Renault 4 and early Renault 5 feature a shifter in the dash panel. This was cheaper to manufacture than

840-517: A column-mounted manual shifter. Outside North America, the column-mounted shifter remained in production. All Toyota Crown and Nissan Cedric taxis in Hong Kong had the 4-speed column shift until 1999 when automatic transmissions were first offered. Since the late 1980s or early 1990s, a 5-speed column shifter has been offered in some vans sold in Asia and Europe, such as Toyota Hiace , Mitsubishi L400 and

960-508: A constant angular velocity while the vehicle moves at varying speeds. CVTs are used in cars , tractors , UTVs , motor scooters , snowmobiles , and earthmoving equipment . The most common type of CVT uses two pulleys connected by a belt or chain , however, several other designs have also been used. A dual-clutch transmission (DCT, sometimes referred to as a twin-clutch transmission , or double-clutch transmission ) uses two separate clutches for odd and even gear sets . The design

1080-428: A conventional manual transmission. They have a gear shifter which requires the driver's input to manually change gears, but the driver is not required to engage a clutch pedal before changing gear. Instead, the mechanical linkage for the clutch pedal is replaced by an actuator , servo , or solenoid and sensors , which operate the clutch system automatically when the driver touches or moves the gearshift . This removes

1200-444: A designated transmission control unit (TCU) for the clutch and shifting, plus steering wheel-mounted paddle shifters, if the driver wanted to change gear manually. Modern fully automatic AMTs, such as Selespeed and Easytronic , have now been largely superseded and replaced by the increasingly widespread dual-clutch transmission design. Power band The power band of an internal combustion engine or electric motor

1320-479: A form of manual transmission which removed the reliance on the driver's skill to achieve smooth gear shifts. The first automatic transmission using hydraulic fluid was developed in 1932 by two Brazilian engineers, José Braz Araripe and Fernando Lehly Lemos. The evolution towards mass-produced automatic transmissions continued with the 1933–1935 REO Motor Car Company Self-Shifter semi-automatic transmission, which automatically shifted between two forward gears in

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1440-451: A gear requires the engine RPM to be at the exact speed that matches the road speed for the gear being selected). Most motor vehicles use a pedal to operate the clutch; except for motorcycles, which usually have a clutch lever on the left handlebar . In most vehicles with a manual transmission, the driver selects gears by manipulating a lever called a gear stick (also called a gearshift , gear lever or shifter ). In most automobiles,

1560-413: A manual transmission. The 1904 Sturtevant "horseless carriage gearbox" is often considered to be the first automatic transmission for motor vehicles. At higher engine speeds, high gear was engaged. As the vehicle slowed down and engine speed decreased, the gearbox would shift back to low. However, the transmission was prone to sudden failure, due to the transmission being unable to withstand forces from

1680-484: A mechanical linkage to connect the shifter to the transmission. Some vehicles have a gear lever mounted on the steering column. A 3-speed column shifter, which came to be popularly known as a "three on the tree", began appearing in America in the late 1930s and became common during the 1940s and 1950s. If a U.S. vehicle was equipped with overdrive , it was very likely to be a Borg-Warner type, operated by briefly backing off

1800-510: A modern, well designed and engineered fuel-injected , computer-controlled , multi-valve and optionally variable-valve timing -equipped gasoline engine using good fuel can achieve remarkable flexibility in automobile applications, with sufficient torque even at low engine speeds and a relatively flat power output from 1,500 to 6,500 RPM, allowing easy cruising and forgiving low-speed behaviour. However, achieving maximum power for strong acceleration or high road speed still requires high RPM. Though

1920-539: A narrow range of rates of rotation, requiring a gearbox , operated manually or automatically, to drive the wheels over a wide range of speeds. The most common type of automatic transmission is the hydraulic automatic , which uses a planetary (epicyclic) gearset , hydraulic controls , and a torque converter . Other types of automatic transmissions include continuously variable transmissions (CVT), automated manual transmissions (AMT), and dual-clutch transmissions (DCT). The 1904 Sturtevant "horseless carriage gearbox"

2040-456: A patent was approved in the United States describing the operation of a transmission where the manual shifting of gears and manual operation of a clutch was eliminated. This patent was submitted by Henry R. Hoffman from Chicago and was titled: Automatic Gear Shift and Speed Control . The patent described the workings of such a transmission as "...having a series of clutches disposed intermediate

2160-445: A separate transmission control unit . This allows for more precise control of shift points, shift quality, lower shift times and manual control. The first five-speed automatic was the ZF 5HP18 transmission , debuting in 1991 on various BMW models. The first six-speed automatic was the ZF 6HP26 transmission , which debuted in the 2002 BMW 7 Series (E65) . The first seven-speed automatic was

2280-440: A switch or pressing a button on the gearshift knob or on the steering column, or automatically by momentarily lifting the foot from the accelerator with the vehicle traveling above a certain road speed. Automatic overdrives were disengaged by flooring the accelerator, and a lockout control was provided to enable the driver to disable overdrive and operate the transmission as a normal (non-overdrive) transmission. The term 'overdrive'

2400-484: A synchromesh and teeth on each side in order to lock either gear to the shaft. Unlike some other types of clutches (such as the foot-operated clutch of a manual-transmission car), a dog clutch provides non-slip coupling and is not suited to intentional slipping. In order to provide smooth gearshifts without requiring the driver to manually match the engine revs for each gearshift, most modern passenger car transmissions use 'synchromesh' (also called 'synchronizer rings') on

2520-404: A synchromesh system for the reverse gear, thus preventing possible crunching if reverse gear is selected while the input shaft is still spinning. Most transmissions include a lockout mechanism to prevent reverse gear from being accidentally selected while the car is moving forwards. This can take the form of a collar underneath the gear knob which needs to be lifted or requiring extra force to push

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2640-409: A three-speed manual transmission. This transmission, along with many similar designs that it inspired, was a 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

2760-429: Is also used to describe a gear with a ratio of less than one (e.g., if the top gear of the transmission has a ratio of 0.8:1). Vehicles with a manual transmission can often be push started when the starter motor is not operational, such as when the car has a dead battery or when the starter motor itself has malfunctioned and is unable to deliver sufficient rotational energy to turn the engine over. When push-starting,

2880-577: Is attributed to the increasing number of electric and hybrid cars, and the ease of integrating it with safety systems such as Autonomous Emergency Braking . The efficiency, power output as a percentage of input, of conventional automatic transmissions ranges from 86 to 94%. Manual transmissions are more fuel efficient than all but the newest automatic transmissions due to their inherently low parasitic losses, typically of about 4%, in addition to being cheaper to make, lighter, better performing, and of simpler mechanical design. However, manual transmissions have

3000-521: Is connected to the engine via a torque converter (or a fluid coupling prior to the 1960s), instead of the friction clutch used by most manual transmissions . A hydraulic automatic transmission uses planetary gearsets instead of the manual transmission's design of gears lined up along input, output and intermediate shafts. To change gears, the hydraulic automatic uses a combination of internal clutches, friction bands or brake packs. These devices are used to lock certain gears, thus setting which gear ratio

3120-427: Is connected via a pinion gear at the end of the counter/output shaft. In a modern constant-mesh manual transmission, the gear teeth are permanently in contact with each other, and dog clutches (sometimes called dog teeth ) are used to select the gear ratio for the transmission. When the dog clutches for all gears are disengaged (i.e. when the transmission is in neutral), all of the gears are able to spin freely around

3240-404: Is in use at a given time. A sprag clutch (a ratchet-like device which can freewheel and transmits torque in only one direction) is often used for routine gear shifts. The advantage of a sprag clutch is that it eliminates the sensitivity of timing a simultaneous clutch release/apply on two planetary gearsets, simply "taking up" the drivetrain load when actuated, and releasing automatically when

3360-449: Is integrated into the engine control unit (ECU). Modern designs have replaced the centrifugal governor with an electronic speed sensor that is used as an input to the TCU or ECU. Modern transmissions also factor in the amount of load on an engine at any given time, which is determined from either the throttle position or the amount of intake manifold vacuum. The multitude of parts, along with

3480-745: Is not considered a manual transmission. Some automatic transmissions are based on the mechanical build and internal design of a manual transmission but have added components (such as computer -controlled actuators and sensors ) which automatically control the timing and speed of the gear shifts and clutch; this design is typically called an automated manual transmission (or sometimes a clutchless manual transmission ). Contemporary manual transmissions for cars typically use five or six forward gears ratios and one reverse gear, however, transmissions with between two and seven gears have been produced at times. Transmissions for trucks and other heavy equipment often have between eight and twenty-five gears, in order to keep

3600-454: Is not possible to push start a vehicle equipped with an automatic transmission with no rear pump (aside from several automatics built prior to 1970, which also included a rear pump for towing and push-starting purposes). The pressure of the ATF is regulated by a governor connected to the output shaft, which varies the pressure depending on the vehicle speed. The valve body inside the transmission

3720-554: Is often considered to be the first true automatic transmission. The first mass-produced automatic transmission is the General Motors Hydramatic four-speed hydraulic automatic, which was introduced in 1939. Automatic transmissions are also found in some heavy commercial vehicles, particularly those which are subject to intense stop/start operation such as buses and waste collection vehicles . Vehicles with internal combustion engines, unlike electric vehicles, require

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3840-505: Is often similar to two separate manual transmissions with their respective clutches contained within one housing, and working as one unit. In most car and truck applications, the DCT functions as an automatic transmission, requiring no driver input to change gears. The first DCT to reach production was the Easidrive automatic transmission introduced on the 1961 Hillman Minx mid-size car. This

3960-450: Is pressurized by a pump and then directed to the appropriate bands/clutches to obtain the required gear ratio. The ATF provides lubrication, corrosion prevention, and a hydraulic medium to transmit the power required to operate the transmission. Made from petroleum with various refinements and additives, ATF is one of the few parts of the automatic transmission that needs routine service as the vehicle ages. The main pump which pressurises

4080-403: Is responsible for directing hydraulic pressure to the appropriate bands and clutches. It receives pressurized fluid from the main pump and consists of several spring-loaded valves, check balls, and servo pistons. In older automatic transmissions, the valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as other inputs, such as throttle position or

4200-423: Is selected, the idler gear is physically moved to mesh with the corresponding gears on the input and output shafts. To avoid grinding as the gears begin to the mesh, they need to be stationary. Since the input shaft is often still spinning due to momentum (even after the car has stopped), a mechanism is needed to stop the input shaft, such as using the synchronizer rings for fifth gear. However, some vehicles do employ

4320-431: Is the product of torque multiplied by speed of rotation (analogous to force multiplied by speed in a linear system), so peak power is produced in the upper speed range where there's both high torque and high RPM. In turbocharged and supercharged engines with potential for abundant torque, an intake pressure regulation system often limits torque to a near-constant figure across the engine speed range to reduce stresses on

4440-415: Is the range of operating speeds under which the engine or motor is able to output the most power , that is, the maximum energy per unit of time. This usually means that maximum acceleration can be achieved inside this band (often at the cost of lower efficiency). While engines and motors have a large range of operating speeds, the power band is usually a much smaller range of engine speed, only half or less of

4560-404: Is used to reverse the direction in which the output shaft rotates. In many transmissions, the input and output shafts can be directly locked together (bypassing the countershaft) to create a 1:1 gear ratio which is referred to as direct-drive . In a transmission for longitudinal engined vehicles (e.g. most rear-wheel-drive cars), it is common for the input shaft and output shaft to be located on

4680-462: Is usually via the left-foot (or, on older motorcycles; right-foot) shift lever with a layout of 1–N–2–3–4–5–6. During the period when U.S. vehicles usually had only three forward speeds, the most common gear-shifter location was on the steering column, a layout that was sometimes called "three on the tree". By contrast, high-performance cars, and European vehicles in general, mostly used a four-speed transmission with floor-mounted shifters. That layout

4800-647: The Honda Element , the Honda Civic , the Daihatsu Sigra , and the Honda Avancier , may feature a manual or automatic transmission gear shifter located on the vehicle's instrument panel, similar to the mid-1950s Chryslers and Powerglide Corvairs . Console-mounted shifters are similar to floor-mounted gear shifters in that most of the ones used in modern vehicles operate on a horizontal plane and can be mounted to

4920-615: The Mercedes-Benz 7G-Tronic transmission , which debuted a year later. In 2007, the first eight-speed transmission to reach production was the Toyota AA80E transmission . The first nine-speed and ten-speed transmissions were the 2013 ZF 9HP transmission and 2017 Toyota Direct Shift-10A (used in the Lexus LC ) respectively. The gear selector is the input by which the driver selects the operating mode of an automatic transmission. Traditionally

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5040-475: The clutch system automatically — and use different forms of actuation (usually via an actuator or servo ) to automate the clutch, but still require the driver's input and full control to manually actuate gear changes by hand. Modern versions of these systems that are fully automatic in operation, such as Selespeed and Easytronic , require no driver input over gear changes or clutch operation. Semi-automatic versions require only partial driver input (i.e.,

5160-400: The hydraulic automatic transmission (AT) and the continuously variable transmission (CVT). The automated manual transmission (AMT) and dual-clutch transmission (DCT) are internally similar to a conventional manual transmission, but are shifted automatically. Alternatively, there are semi-automatic transmissions . These systems are based on the design of, and are technically similar to,

5280-427: The splines on the shaft, forcing that shaft to rotate at the same speed as the gear hub. However, the clutch can move back and forth on the shaft, to either engage or disengage the splines. This movement is controlled by a selector fork that is linked to the gear lever. The fork does not rotate, so it is attached to a collar bearing on the selector. The selector is typically symmetric: it slides between two gears and has

5400-415: The stereo system or HVAC system , to help prevent accidental activation or driver confusion. More and more small cars and vans from manufacturers such as Suzuki , Honda , and Volkswagen are featuring console shifters in that they free up space on the floor for other features such as storage compartments without requiring that the gear shift be mounted on the steering column. Also, the basic location of

5520-618: The "Forward" mode (or between two shorter gear ratios in the "Emergency low" mode). Driver involvement was still required during normal driving, since standing starts required the driver to use the clutch pedal. This was followed in 1937 by the Oldsmobile Automatic Safety Transmission . Similar in operation to the REO Self-Shifter , the Automatic Safety Transmission shifted automatically between

5640-471: The 1948 Ferrari 166 Inter and the 1953 Alfa Romeo 1900 Super Sprint . Five-speed transmissions became widespread during the 1980s, as did the use of synchromesh on all forward gears. Six-speed manual transmissions started to emerge in high-performance vehicles in the early 1990s, such as the 1990 BMW 850i and the 1992 Ferrari 456 . The first 6-speed manual transmission was introduced in the 1967 Alfa Romeo 33 Stradale . The first 7-speed manual transmission

5760-424: The 1980s, automatic transmissions with four gear ratios became increasingly common, and many were equipped with lock-up torque convertors in order to improve fuel economy. Electronics began to be more commonly used to control the transmission, replacing mechanical control methods such as spring-loaded valves in the valve body. Most systems use solenoids which are controlled by either the engine control unit , or

5880-406: The 1990s, systems to manually request a specific gear or an upshift/downshift have become more common. These manumatic transmissions offer the driver greater control over the gear selection that the traditional modes to restrict the transmission to the lower gears. Use of the manumatic functions are typically achieved either via paddles located beside the steering column, or "+" and "-" controls on

6000-425: The ATF is typically a gear pump mounted between the torque converter and the planetary gear set. The input for the main pump is connected to the torque converter housing, which in turn is bolted to the engine's flexplate, so the pump provides pressure whenever the engine is running. A disadvantage of this arrangement is that there is no oil pressure to operate the transmission when the engine is not running, therefore it

6120-529: The Corvair. Most cars use a "P–R–N–D–L" layout for the gear selector, which consists of the following positions: Some automatic transmissions, especially by General Motors from 1940 to 1964, used a layout with reverse as the bottom position (e.g. N–D–L–R or P–N–D–L–R). Many transmissions also include positions to restrict the gear selection to the lower gears and engages the engine brake . These positions are often labelled "L" (low gear), "S" (second gear) or

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6240-610: The Hydra-Matic included a wide spread of ratios (allowing both good acceleration in first gear and cruising at low engine speed in top gear) and the fluid coupling handling only a portion of the engine's torque in the top two gears (increasing fuel economy in those gears, similar to a lock-up torque converter). Use of the Hydra-Matic spread to other General Motors brands and then to other manufacturers starting 1948 including Hudson , Lincoln , Kaiser , Nash , Holden (Australia), as well as Rolls-Royce and Bentley licensing production in

6360-523: The U.S. and Canada had a 3-speed column-mounted shifter—the first generation Chevrolet/GMC vans of 1964–70 vintage had an ultra-rare 4-speed column shifter. The column-mounted manual shifter disappeared in North America by the mid-1980s, last appearing in the 1987 Chevrolet pickup truck . Prior to 1980, the GM X platform compacts (Chevrolet Nova and its rebadged corporate clones) were the final passenger cars to have

6480-563: The UK and providing the transmission to Jensen Motors , Armstrong Siddeley and other UK manufacturers. During World War II, the Hydra-Matic was used in some military vehicles. The first automatic transmission to use a torque converter (instead of a fluid coupling) was the Buick Dynaflow , which was introduced for the 1948 model year. In normal driving, the Dynaflow used only the top gear, relying on

6600-711: The United States had automatic transmissions. Automatic transmissions have been standard in large cars since at least 1974. By 2020 only 2.4% of new cars had manual transmissions. Historically, automatic transmissions were less efficient, but lower fuel prices in the US made this less of a problem than in Europe. In the United Kingdom, a majority of new cars have had automatic transmissions since 2020. Several manufacturers including Mercedes and Volvo no longer sell cars with manual transmissions. The growing prevalence of automatic transmissions

6720-429: The abrupt gear changes. The adoption of planetary gearsets was a significant advance towards the modern automatic transmission. One of the first transmissions to use this design was the manual transmission fitted to the 1901–1904 Wilson-Pilcher automobile. This transmission was built in the United Kingdom and used two epicyclic gears to provide four gear ratios. A foot clutch was used for standing starts, gear selection

6840-455: The accelerator pedal when above 28 mph (45 km/h) to enable, and momentarily flooring the same pedal to return to normal gear. The control simply disables overdrive for such situations as parking on a hill or preventing unwanted shifting into overdrive. [REDACTED] Later, European and Japanese models began to have 4-speed column shifters with this shift pattern: [REDACTED] A majority of North American-spec vehicles sold in

6960-486: The clutch). Larger differences in speed between the input shaft and the gear require higher friction forces from the synchromesh components, potentially increasing their wear rate. Even in modern transmissions where all of the forward gears are in a constant-mesh configuration, often the reverse gear uses the older sliding-mesh ("crash box") configuration. This means that moving the gearshift lever into reverse results in gears moving to mesh together. Another unique aspect of

7080-484: The collar from bridging the locking rings while the speeds are still being synchronized. This is achieved through 'blocker rings' (also called 'baulk rings'). The synchro ring rotates slightly because of the frictional torque from the cone clutch. In this position, the dog clutch is prevented from engaging. Once the speeds are synchronized, friction on the blocker ring is relieved and the blocker ring twists slightly, bringing into alignment certain grooves or notches that allow

7200-401: The complex design of the valve body, originally made hydraulic automatic transmissions much more expensive and time-consuming to build and repair than manual transmissions; however mass-production and developments over time have reduced this cost gap. To provide coupling and decoupling of the engine, a modern automatic transmission uses a torque converter instead of the friction clutch used in

7320-461: The cone-shaped sleeve on the dog collar so that the friction forces can reduce the difference in rotational speeds. Once these speeds are equalized, the dog clutch can engage, and thus the new gear is now in use. In a modern gearbox, the action of all of these components is so smooth and fast it is hardly noticed. Many transmissions do not include synchromesh on the reverse gear (see Reverse gear section below). The synchromesh system must also prevent

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7440-419: The cranking motion being replaced by the pushing of the car. 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. Vehicles with internal combustion engines , unlike electric vehicles , require the engine to operate in

7560-403: The disadvantage of requiring the driver to operate the clutch and change the gear whenever required. Fuel economy of course worsens with lower efficiency. Real-world tests reported in 2022 found that in typical driving manual transmissions achieved 2 to 5% better fuel economy than automatics, increasing to 20% with an expert driver. Some laboratory tests show automatics in a better light due to

7680-437: The dog clutch to fall into the engagement. Common metals for synchronizer rings are brass and steel , and are produced either by forging or sheet metal shaping. The latter involves stamping the piece out of a sheet metal strip and then machining to obtain the exact shape required. The rings are sometimes coated with anti-wear linings (also called 'friction linings') made from molybdenum , iron , bronze or carbon (with

7800-427: The dog clutches require the input shaft speed to match that of the gear being selected; otherwise, the dog teeth will fail to engage and a loud grinding sound will be heard as they clatter together. Therefore, to speed up or slow down the input shaft as required, cone-shaped brass synchronizer rings are attached to each gear. When the driver moves the gearshift lever towards the next gear, these synchronizer rings press on

7920-446: The driver locking out the higher gears) to control which ratio is selected. As the vehicle and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. In more recent automatic transmissions, the valves are controlled by solenoids . These solenoids are computer-controlled, with the gear selection decided by a dedicated transmission control unit (TCU) or sometimes this function

8040-402: The driver must change gears manually), while fully automatic versions require no manual driver input, whatsoever ( TCU or ECU operates both the clutch system and gear shifts automatically). Modern automated manual transmissions (AMT) have their roots and origins in older clutchless manual transmissions that began to appear on mass-production automobiles in the early 1930s and 1940s, prior to

8160-417: The driver to select the next-higher or next-lower gear. In a vehicle with a manual transmission, the flywheel is attached to the engine's crankshaft , therefore rotating at engine speed. A clutch disc sits between the flywheel and the transmission pressure plate which is attached to the transmission input shaft, controlling whether the transmission is connected to the engine or not. The clutch pedal controls

8280-413: The early 1950s, most cars only had synchromesh for the shift from third gear to second gear (drivers' manuals in vehicles suggested that if the driver needed to shift from second to first, it was best to come to a complete stop beforehand). Up until the late 1970s, most transmissions had three or four forward gear ratios, although five-speed manual transmissions were occasionally used in sports cars such as

8400-407: The energy generated by the wheels moving on the road is transferred to the driveshaft, then the transmission, and eventually the crankshaft. When the crankshaft spins as a result of the energy generated by the rolling of the vehicle, the motor is cranked over. This simulates what the starter is intended for and operates in a similar way to crank handles on very old cars from the early 20th century, with

8520-527: The engine and provide consistent handling without decreasing peak power. Powerbands can surpass 14,000 RPM in motorcycles and some racing automobiles, such as Formula One cars . Such high speeds are reached by using lightweight pistons and connecting rods with short strokes to reduce inertia, and thus stresses on parts. Advances in valve technology similarly reduce valve float at such speeds. As an engine grows larger (its stroke in particular), its power band moves to lower speeds. In more common applications,

8640-436: The engine from labouring at low speeds, or exceeding recommended operating speeds. A narrow power band is often compensated for by a power-splitting device such as a clutch or torque converter to efficiently achieve a wide range of speeds. A continuously variable transmission can also avoid the issues of a narrow power band by keeping the engine running at an optimal speed. In typical combustion engines found in vehicles,

8760-411: The engine shaft and the differential shaft and in which the clutches are arranged to selectively engage and drive the differential shaft dependent upon the speed at which the differential shaft rotates". However, it would be over a decade later until automatic transmissions were produced in significant quantities. In the meantime, several European and British manufacturers would use preselector gearboxes ,

8880-456: The engine speed within the optimal power band for all typical road speeds. Operating such transmissions often uses the same pattern of shifter movement with a single or multiple switches to engage the next sequence of gears. Many of the first automobiles were rear-engined, with a simple belt-drive functioning as a single-speed transmission. The 1891 Panhard et Levassor is considered a significant advance in automotive transmissions since it used

9000-494: The engine to operate in a narrow range of rates of rotation, requiring a gearbox, operated manually or automatically, to drive the wheels over a wide range of speeds. Globally, 43% of new cars produced in 2015 were manual transmissions, falling to 37% by 2020. Automatic transmissions have long been prevalent in the United States, but only started to become common in Europe much later. In Europe in 1997, only 10–12% of cars had automatic transmissions. In 1957 over 80% of new cars in

9120-399: The fifth selector on the main shaft. This means that when the vehicle is stopped and idling in neutral with the clutch engaged and the input shaft spinning, the third-, fourth-, and fifth-gear pairs do not rotate. When neutral is selected, none of the gears on the output shaft are locked to the shaft, allowing the input and output shafts to rotate independently. For reverse gear, an idler gear

9240-583: The first mass-produced automatic transmission following its introduction in 1939 (1940 model year). Available as an option in cars such as the Oldsmobile Series 60 and Cadillac Sixty Special , the Hydra-Matic combined a fluid coupling with three hydraulically controlled planetary gearsets to produce four forward speeds plus reverse. The transmission was sensitive to engine throttle position and road speed, producing fully automatic up- and down-shifting that varied according to operating conditions. Features of

9360-521: The first-gen Fiat Ducato . Many European cars had manual column shifts and the Renault 16TX had a 5 speed. Column shifters are mechanically similar to floor shifters, although shifting occurs in a vertical plane instead of a horizontal one. Because the shifter is further away from the transmission, and the movements at the shifter and at the transmission are in different planes, column shifters require more complicated linkage than floor shifters. Advantages of

9480-438: The forces required or provide a faster shift time . The first car to use a manual transmission with synchromesh was the 1929 Cadillac . Most North American marques had adopted synchronized manual transmissions, usually for second and high gears, by the mid-1930s. In 1947, Porsche patented the split ring synchromesh system. The 1952 Porsche 356 was the first car to use a transmission with synchromesh on all forward gears. In

9600-400: The forward gears. These devices automatically match the speed of the input shaft with that of the gear being selected, thus removing the need for the driver to use techniques such as double-clutching . The synchromesh transmission was invented in 1919 by Earl Avery Thompson and first used on production cars by Cadillac in 1928. The need for synchromesh in a constant-mesh transmission is that

9720-418: The front-wheel-drive transaxle's ring gear. This allows for a narrower transmission since the length of each countershaft is halved compared with one that contains four gears and two shifters. The fixed and free gears can be mounted on either the input or output shaft or both. For example, a five-speed transmission might have the first-to-second selectors on the countershaft, but the third-to-fourth selector and

9840-433: The gear selector is located between the two front seats or on the steering column, however electronic rotary dials and push-buttons have also been occasionally used since the 1980s, as well as push buttons having been used in the 1950s and 1960s by Rambler (automobile) , Edsel , and most famously, by Chrysler . A few automobiles employed a lever on the instrument panel, such as the 1955 Chrysler Corporation cars, and notably,

9960-401: The gear selector. Some cars offer drivers both methods to request a manual gear selection. A continuously variable transmission (CVT) can change seamlessly through a continuous (infinite) range of gear ratios, compared with other automatic transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at

10080-437: The gear shift in comparison to the column shifter makes console shifters easier to operate than column shifters. In the 1950s, 1960s, and 1970s, fuel-efficient highway cruising with low engine speed was in some cases enabled on vehicles equipped with 3- or 4-speed transmissions by means of a separate overdrive unit in or behind the rear housing of the transmission. This was actuated either manually while in high gear by throwing

10200-443: The gear stick is located on the floor between the driver and front passenger, but some cars have a gear stick that is mounted to the steering column or center console. The movement of the gear stick is transferred (via solid linkages or cables) to the selector forks within the transmission. Motorcycles typically employ sequential manual transmissions , although the shift pattern is modified slightly for safety reasons. Gear selection

10320-476: The gearshift lever into the plane of reverse gear. Another design of transmission that is used in older cars , trucks , and tractors , is a non-synchronous transmission (also known as a crash gearbox). Non-synchronous transmissions use a sliding-mesh (or constant-mesh, in later years) design and have the nickname "crash" because the difficulty in changing gears can lead to gear shifts accompanied by crashing/crunching noises. Vehicles with manual transmissions use

10440-406: The introduction of hydraulic automatic transmissions. These systems were designed to reduce the amount of clutch or gear shifter usage required by the driver. These devices were intended to reduce the difficulty of operating conventional unsynchronised manual transmissions ("crash gearboxes") that were commonly used at the time, especially in stop-start driving. An early example of this transmission

10560-436: The latter usually reserved for high-performance transmissions due to their high cost). Mechanical wear of the synchronizer rings and sleeves can cause the synchromesh system to become ineffective over time. These rings and sleeves have to overcome the momentum of the entire input shaft and clutch disk during each gearshift (and also the momentum and power of the engine, if the driver attempts a gearshift without fully disengaging

10680-404: The literal power band covers most of the operating RPM range, particularly in first gear (as there is no lower gear to shift down to, and no "flat spot" in which the engine does not produce any power), the effective band changes in each gear, becoming the range limited at the upper end by either the limiter, or a point roughly located between peak power and the redline where power drops off, and at

10800-487: The lower end the engine's idling speed. A typical road-going ("high-speed") diesel has a narrower band, generating peak torque at lower RPM (often 1,500–2,000 RPM) but also with a sharper fall-off below this, and reaching peak power around 3500-4500 RPM, again rapidly losing strength above this speed. Turbocharged diesel engines with turbo lag (narrowed, exaggerated power band intrinsic to most turbocharged engines) may display this characteristic even more markedly. Therefore,

10920-678: The manufacturer's (or purchaser's/modifier's) choice of gearing, and appropriate use of the available ratios, is even more crucial to make best use of the available power and avoid being "bogged down" in flat spots. Larger diesel engines in locomotives and some watercraft use diesel-electric drives. This eliminates the complexities of extremely low gearing, as described below. The largest ("low-speed") diesels—large generators on land and marine diesels at sea—may turn at only hundreds of RPM or even below, with idling speeds of 20-30 RPM. These engines are usually two-stroke diesel engines . Electric motors are unique in many ways, especially when it comes to

11040-573: The need for a physical clutch pedal. A manual transmission requires the driver to operate the gear stick and clutch in order to change gears (unlike an automatic transmission or semi-automatic transmission , where one (typically the clutch) or both of these functions are automated ). Most manual transmissions for cars allow the driver to select any gear ratio at any time, for example shifting from second to fourth gear, or fifth to third gear. However, sequential manual transmissions , which are commonly used in motorcycles and racing cars , only allow

11160-443: The next gear's sprag clutch assumes the torque transfer. The friction bands are often used for manually selected gears (such as low range or reverse) and operate on the planetary drum's circumference. Bands are not applied when the drive/overdrive range is selected, the torque being transmitted by the sprag clutches instead. The aforementioned friction bands and clutches are controlled using automatic transmission fluid (ATF), which

11280-681: The number of the highest gear used in that position (eg 3, 2 or 1). If these positions are engaged at a time when it would result in excessive engine speed, many modern transmissions disregard the selector position and remain in the higher gear. In descending order of the highest gear available: Many modern transmissions include modes to adjust the shift logic to prefer either power or fuel economy . "Sport" (also called "Power" or "Performance") modes cause gear shifts to occur at higher engine speeds, allowing higher acceleration. "Economy" (also called "Eco" or "Comfort") modes cause gear shifts to occur at lower engine speeds to reduce fuel consumption. Since

11400-406: The other shaft, with a bearing located between the two shafts. In a transmission for transverse engined vehicles (e.g., front-wheel-drive cars), there are usually only two shafts: input and countershaft (sometimes called input and output). The input shaft runs the whole length of the gearbox, and there is no separate input pinion. These transmissions also have an integral differential unit, which

11520-483: The output shaft gears are able to rotate independently of the output shaft itself (through the use of bearings located between the gears and the shaft). Through the use of collars (operated using the shift rods ), the speed of the output shaft becomes temporarily locked to the speed of the selected gear. Some transmission designs—such as in the Volvo 850 and S70—have two countershafts, both driving an output pinion meshing with

11640-401: The output shaft inside the transmission. This is a fundamental difference compared with a typical hydraulic automatic transmission , which uses an epicyclic (planetary) design, and a hydraulic torque converter . An automatic transmission that allows the driver to control the gear selection (such as shift paddles or "+/-" positions on the gear selector) is called a manumatic transmission, and

11760-423: The output shaft. When the driver selects a gear, the dog clutch for that gear is engaged (via the gear selector rods), locking the transmission's output shaft to a particular gear set. This means the output shaft rotates at the same speed as the selected gear, thus determining the gear ratio of the transmission. The dog clutch is a sliding selector mechanism that sits around the output shaft. It has teeth to fit into

11880-510: The power band. The exact characteristics vary greatly with the type of electric motor. The maximum torque of a universal motor (vacuum cleaner, small machines, drills, starter motors) occurs at zero rotation rate (when stalled) and falls for higher RPM. For induction motors connected to a fixed frequency AC source (most common in large applications), the maximum torque is usually just below the synchronous RPM, sinks to zero for this RPM and becomes negative above it (induction generator); at low RPM

12000-480: The power peak below 5,000 RPM. A mechanical transmission with a selection of different gear ratios is designed to make satisfactory power available over the full range of vehicle speeds. The goal of the selection of gear ratios is to keep the engine operating in its power band. The narrower the band, the more gears are needed, closer together in ratio. By careful gear selection, an engine can be operated in its power band, throughout all vehicle speeds. Such use prevents

12120-444: The pressure plate ( clutch engaged – the clutch pedal is not being pressed) or not connected to the engine ( clutch disengaged – the clutch pedal is being pressed down). When the engine is running and the clutch is engaged (i.e., clutch pedal up), the flywheel spins the clutch pressure plate and hence the transmission. The design of most manual transmissions for cars is that gear ratios are selected by locking selected gear pairs to

12240-430: The reverse gear is that it consists of two gears—an idler gear on the countershaft and another gear on the output shaft—and both of these are directly fixed to the shaft (i.e. they are always rotating at the same speed as the shaft). These gears are usually spur gears with straight-cut teeth which—unlike the helical teeth used for forward gear—results in a whining sound as the vehicle moves in reverse. When reverse gear

12360-401: The same axis, since this reduces the torsional forces to which the transmission casing must withstand. The assembly consisting of both the input and output shafts is referred to as the main shaft (although sometimes this term refers to just the input shaft or output shaft). Independent rotation of the input and output shafts is made possible by one shaft being located inside the hollow bore of

12480-440: 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". 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

12600-424: The tests using a prescribed shifting pattern for manuals not always optimized for economy. However, on long highway journeys manual transmissions require maintaining a very specific cruising speed to optimise economy, making automatics preferable. The most common design of automatic transmissions is the hydraulic automatic, which typically uses planetary gearsets that are operated using hydraulics. The transmission

12720-559: The torque is low at idling speed, reaches a maximal value between 1,500 and 6,500 RPM, and then falls more or less sharply toward the redline. Below the RPM of maximal torque, the intake air velocity and thus mixing of air and fuel is not ideal. Above this speed several factors start to limit the torque, such as growing friction, the required time for closing the valves and combustion, and insufficient intake flow. Due to increasing vibration and heat, an external RPM limitation may also be installed. Power

12840-696: The torque is usually slightly lower. Synchronous motors can be used only at the AC source synchronous velocity. In modern applications, synchronous and induction motors with electronic control of the frequency are used, e.g., brushless DC electric motors . In this case, unless external limitations are applied, the maximum torque is achieved at low RPM. For example, the AC motor found in the Tesla Roadster (2008) produces near constant maximum torque from 0 to about 6000 RPM, while maximum power occurs at about 10000 RPM, long after torque begins to drop off. The Roadster's redline

12960-605: The torque multiplication of the torque convertor at lower speeds. The Dynaflow was followed by the Packard Ultramatic in mid-1949 and the Chevrolet Powerglide for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the converter for additional torque multiplication. In the early 1950s, BorgWarner developed a series of three-speed torque converter automatics for car manufacturers such as American Motors, Ford and Studebaker. Chrysler

13080-539: The total engine speed range (electric motors are an exception—see the section on electric motors below). Specifically, power band is the range of RPM around peak power output. The power band of an internal combustion gasoline automobile engine typically starts at midrange engine speeds (around 4,000 RPM) where maximum torque is produced, and ends below the redline after reaching maximum power (above 5,000 RPM but less than 7,000 RPM). Diesel engines in cars and small trucks may develop maximum torque below 2,000 RPM with

13200-441: The two gear ratios available in the "Low" and "High" ranges and the clutch pedal was required for standing starts. It used a planetary gearset. The Chrysler Fluid Drive , introduced in 1939, was an optional addition to manual transmissions where a fluid coupling (similar to a torque-convertor, but without the torque multiplication) was added, to avoid the need to operate a manual clutch. The General Motors Hydra-Matic became

13320-467: The vehicle's transmission in much the same way a floor-mounted shifter can. However, because of the location of the gear shifter in comparison to the locations of the column shifter and the floor shifter, as well as the positioning of the shifter to the rest of the controls on the panel often require that the gearshift be mounted in a space that does not feature a lot of controls integral to the vehicle's operation, or frequently used controls, such as those for

13440-418: Was among the first to have the basic gear selections ( park , reverse , neutral , drive , low ) which became the standard gear selection used for several decades. By the late 1960s, most of the fluid-coupling two-speed and four-speed transmissions had disappeared in favor of three-speed units with torque converters. Also around this time, whale oil was removed from the automatic transmission fluid. During

13560-613: Was called the Controlled Coupling Hydra-Matic , or "Jetaway" transmission. The original Hydra-Matic remained in production until the mid-1960s at GM, with the licensed Rolls-Royce Automatic transmission soldiering on until 1978 on the Rolls-Royce Phantom VI . In 1964, General Motors released a new transmission, the Turbo Hydramatic , a three-speed transmission which used a torque convertor. The Turbo Hydramatic

13680-501: Was followed by various eastern European tractors through the 1970s (using manual operation via a single clutch pedal), then the Porsche 962 C racing car in 1985. The first DCT of the modern era was used in the 2003 Volkswagen Golf R32 . Since the late 2000s, DCTs have become increasingly widespread, and have supplanted hydraulic automatic transmissions in various models of cars. Automated manual transmission (AMT) , sometimes referred to as

13800-541: Was introduced in the 1955 Citroën DS , which used a 4-speed BVH transmission. This semi-automatic transmission used an automated clutch, which was actuated using hydraulics . Gear selection also used hydraulics , however, the gear ratio needs to be manually selected by the driver. This system was nicknamed Citro-Matic in the U.S. The first modern AMTs were introduced by BMW and Ferrari in 1997, with their SMG and F1 transmissions, respectively. Both systems used hydraulic actuators and electrical solenoids , and

13920-457: Was introduced in the 2012 Porsche 911 (991) . In 2008, 75.2% of vehicles produced in Western Europe were equipped with manual transmission, versus 16.1% with automatic and 8.7% with other. A manual transmission has several shafts with various gears and other components attached to them. Most modern passenger cars use 'constant-mesh' transmissions consisting of three shafts: an input shaft ,

14040-631: Was introduced with the Hudson Commodore in 1942, called Drive-Master . This unit was an early semi-automatic transmission , based on the design of a conventional manual transmission, which used a servo -controlled vacuum -operated clutch system, with three different gear shifting modes, at the touch of a button; manual shifting and manual clutch operation (fully manual), manual shifting with automated clutch operation (semi-automatic), and automatic shifting with automatic clutch operation (fully automatic). Another early example of this transmission system

14160-532: Was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953, and the three-speed TorqueFlite in 1956. The latter was the first to utilize the Simpson compound planetary gearset. In 1956, the General Motors Hydra-Matic (which still used a fluid coupling) was redesigned based around the use of two fluid couplings to provide smoother shifts. This transmission

14280-412: Was referred to as "four on the floor". Most FR (front-engined, rear-wheel drive) vehicles have a transmission that sits between the driver and the front passenger seat. Floor-mounted shifters are often connected directly to the transmission. FF (front-engined, front-wheel drive) vehicles, RR (rear-engined, rear-wheel drive) vehicles and front-engined vehicles with rear-mounted gearboxes often require

14400-551: Was using a hand lever, helical gears were used (to reduce noise) and the gears used a constant-mesh design. A planetary gearset was also used in the 1908 Ford Model T , which was fitted with a two-speed manual transmission (without helical gears). An early patent for the automatic transmission was granted to Canadian inventor Alfred Horner Munro of Regina in 1923. Being a steam engineer, Munro designed his device to use compressed air rather than hydraulic fluid , and so it lacked power and never found commercial application. In 1923,

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