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77-532: The Dynaflow was an automatic transmission used in various forms in Buick cars by the General Motors Corporation from 1947 until 1963. The transmission initially used a five-element torque converter , with two turbines and two stators , as well as a planetary gearset that provided two forward speeds plus reverse. In normal driving, Dynaflow started in high gear (direct drive), relying on

154-429: 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

231-424: A Buick “family car” wouldn't fare well during the teenage son's weekly “date night Friday” outings. Engine RPM seemed to be more a function of accelerator pedal position than of actual road speed. "Flooring" the accelerator pedal would cause the engine speed to flare (even though there is no automatic downshift and no torque converter lockup to disengage). As the car would accelerate, RPM would further climb, but by

308-508: 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

385-470: 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 Modern fully automatic AMTs, such as Selespeed and Easytronic , have now been largely superseded and replaced by the increasingly widespread dual-clutch transmission design. Revolutions per minute Revolutions per minute (abbreviated rpm , RPM , rev/min , r/min , or r⋅min )

462-486: A disproportionately smaller amount. Even more strangely, manually downshifting (see above) with the gas pedal already "floored" would not increase RPM in proportion to the 1.8:1 drop in gear ratio. The Dynaflow aural experience was similar to that of a Continuously Variable Transmission (CVT) (though modern electronically controlled CVT's address this throttle position dependent engine speed (and sound) characteristic by artificially inserting stepwise ratio changes instead of

539-479: 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

616-538: 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

693-413: 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

770-400: 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

847-606: A second stator was designed into the torque converter at the outer diameter of the turbines. This provided a Stall Ratio of 3.5:1 making the performance comparable to other automatic transmissions of the time. This design continued until the end of production of the Twin Turbine Drive in 1963. However, the Triple Turbine ended production in the end of the 1959 model year, leaving the original Dynaflow Twin Turbine

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924-448: 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

1001-462: A shift quadrant that read P-R-N-D-G (where "G" stood for "grade retard"). The grade retard feature was not designed as a low or forward acceleration gear and was meant to be used only on long declines to generate a degree of engine braking. The Triple Turbine was cancelled after 1959 due to technical problems and poor sales with only the Twin Turbine being produced until 1963. In the late 1950s

1078-526: A truly continuous or constant rate change in order to simulate more driver-satisfying genuine shifts). In 1953, Buick redesigned the Dynaflow, calling it the "Twin Turbine Dynaflow" . The converter now incorporated two turbines and a planetary gear set, with a single stator. The first turbine was linked to the ring gear and the second to the planets, which gave a 2.5:1 torque multiplication which

1155-470: Is angular frequency (or angular speed , the magnitude of angular velocity ), for which the SI unit is the radian per second (rad/s). Although they have the same dimensions (reciprocal time) and base unit (s ), the hertz (Hz) and radians per second (rad/s) are special names used to express two different but proportional ISQ quantities: frequency and angular frequency, respectively. The conversions between

1232-459: 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 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

1309-481: Is a unit of rotational speed (or rotational frequency ) for rotating machines. One revolution per minute is equivalent to ⁠ 1 / 60 ⁠ hertz . ISO 80000-3 :2019 defines a physical quantity called rotation (or number of revolutions ), dimensionless , whose instantaneous rate of change is called rotational frequency (or rate of rotation ), with units of reciprocal seconds (s ). A related but distinct quantity for describing rotation

1386-577: 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

1463-521: 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

1540-404: 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

1617-452: 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

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1694-457: 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

1771-513: 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

1848-450: 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

1925-403: 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

2002-460: 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" is often considered to be the first true automatic transmission. The first mass-produced automatic transmission

2079-522: 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 the engine to operate in a narrow range of rates of rotation, requiring

2156-500: The Hydra-Matic used by its sister GM divisions Oldsmobile , Cadillac and then Pontiac . The contemporary Hydra-Matic, the world's first large scale successful automatic transmission, used a simple two element fluid coupling — a more efficient device than a torque converter but which provided no torque multiplication — to feed power to its fully automatic four speed planetary gearbox. Hydra-Matic's high number of gear ratios for

2233-633: 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

2310-662: The Turbo-Hydramatic . One feature of the Dynaflow, the variable-pitch torque converter stator, colloquially the "Switch-Pitch", lived on in versions of the Turbo-Hydramatic (Super Turbine 400) fitted to full-size Buicks, full-size Oldsmobiles and Cadillacs built from 1965 to 1967, as well as the Buick Super Turbine 300 and Oldsmobile Jetaway from 1964 to 1967. The early 1950s Cadillacs were normally equipped with Hydramatic transmissions. In 1953

2387-475: 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.,

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2464-510: The "Dynaflow" name after 1958). This unit was similar to the Twin Turbine, but had a variable pitch stator that increased converter's torque multiplication to 3:1. The stator element of the torque converter has two blade positions, controlled by the driver via the accelerator pedal to offer a 'passing gear' and extra response at any speed from heavy throttle application. In normal driving the stator blades are arranged at 'cruise' angle, with improved efficiency and response at light throttle. Opening

2541-654: 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

2618-446: The 1950s and early 1960s. But at the time, gasoline was cheap, emissions concerns were nonexistent, and Buicks were upscale cars, so the "gas hog" reputation was not a serious sales deterrent. Manually "downshifting" from the direct drive “Drive range” to the 1.8:1 “Low range” enabled Buick's “torque monster” engines to provide very good acceleration, though frequent “downshifting” took a serious toll on transmission reliability. Arguably,

2695-424: 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

2772-406: 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

2849-425: 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

2926-498: The Buick division of GM collaborated with Darby Buick of Sarasota, Florida to investigate potential marine uses of the Dynaflow transmission. The test boat was a 21-foot Correct Craft . The engine was a 364 CID Buick with a four barrel Rochester carburetor of nominal 300 gross hp. The boat could attain a speed of about 60 mph (96 km/h), which was considerable for the time, but the transmission suffered from two problems. First,

3003-534: 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

3080-559: The General Motors Hydramatic Plant burned to the ground, leaving Cadillac without a source of transmissions. Buick Dynaflow transmissions were hastily adapted to Cadillac mount points, and some 19,000 1953 Series 62 Cadillacs, and some 28,000 Cadillacs of all models, were equipped with Dynaflow transmissions. Several thousand 1953 Oldsmobiles were also equipped with Dynaflow. Automatic transmission An automatic transmission (sometimes abbreviated AT )

3157-616: 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

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3234-522: 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

3311-672: 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

3388-429: 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

3465-401: 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

3542-453: The converter's 3.1:1 torque multiplication to accelerate the vehicle. Low gear, obtained via the planetary gearset, could be manually engaged and held up to approximately 60 mph (97 km/h), improving acceleration. The transmission was incapable of automatic shifting, requiring the driver to move the shift lever from low to drive to cause an upshift. Buicks equipped with the Dynaflow transmissions were unique among American automobiles of

3619-419: The day compensated lack of a torque converter by including an exceptionally low first gear of 4:1. Other contemporary automatics followed the middle ground by using two or three automatic shifting gear ratios along with a relatively simple three element torque converter. Three element torque converters continue to be the norm — albeit "tighter", more efficient and less torque multiplying torque converters — even as

3696-403: 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

3773-446: 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

3850-402: 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

3927-411: 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 ,

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4004-591: 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

4081-433: 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,

4158-401: 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

4235-406: 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

4312-443: 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

4389-502: The number of discrete gear ratios in modern 21st Century automatics continues to increase to as many as ten. Two speed automatics with three element torque converters were common for lower priced cars of the day and in the Chrysler PowerFlite as used in the entire Chrysler Corporation lineup through 1956. Dynaflow's inefficiency earned Buick a reputation as a “gas hog” even when compared to heavy, powerful luxury cars of

4466-681: 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

4543-490: The only automatic available in full-size Buicks. A final version appeared in 1958 incorporating three turbines that Buick named the Flight Pitch Dynaflow. Buick made this transmission standard on its top-of-the-line Roadmaster 75 and Limited models and optional on all others. This version was further refined for 1959 and renamed the Triple Turbine but was offered only as an option on all models (Buick dropped

4620-424: 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

4697-421: The throttle changes the angle of the stator vanes hydraulically to 'performance angle', which permits the converter to achieve stall about 1000 rpm higher than in 'cruise'. In this situation oil is redirected to strike the next-lowest drive turbine, which effectively lowers the drive ratio, and allows engine speed to flare to a speed where output is greatest. A few identifying features: the older Twin Turbine model

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4774-461: The time in that the driver or their passengers would not detect the tell-tale interruption in acceleration that resulted when other automatic transmissions of the time shifted through their gears. Acceleration through a Dynaflow was one smooth (if inefficient and slow) experience. It was because of this slow acceleration that the Dynaflow transmission was nicknamed "Dynaslush." The Dynaflow was an inherently inefficient design due to its sole reliance on

4851-515: The torque converter in normal driving. Exacerbating the situation was the dual stator arrangement, which wasted more power than the simpler three element converters used with other automatic transmissions, such as Chrysler 's TorqueFlite . The multiple stators increased turbulence in the converter, even when operating in the coupling phase. During the Dynaflow era, many of Buick's unique engineering features ranked smoothness above most other design and marketing objectives. Dynaflow's non-shifting design

4928-495: The torque in reverse was excessive, although this could have been alleviated with different gear ratios. Second, the state of "Park" in a car necessitated a stopped drivetrain. Without the locked-in-place tires of a car, it was difficult to put the transmission into the equivalent of "Park." In 1964, the Dynaflow was discontinued in favor of the more efficient Super Turbine 300 two-speed and Super Turbine 400 three-speed transmissions, Super Turbine 400 being Buick's trade name for

5005-622: 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

5082-441: 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

5159-400: Was a simple design that enabled Buick to use soft coil springs while its competitors, including its corporate cousins, used harsher, firmer leaf spring , Hotchkiss drive rear suspension. Dynaflow's smooth but inefficient five element torque converter which fed power through a non-shifting direct drive (plus one manually selectable "Low gear" of 1.8:1) was the conceptual polar opposite from

5236-418: 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

5313-644: 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

5390-469: Was demonstrably smoother than the rough shifting automatics then available. Moreover, Buick's torque tube " live axle " rear suspension design, which incorporated a rigid drive shaft with just one single universal joint ("U-joint") at the front end of the driveshaft, was said to amplify the harshness of contemporary automatic shifting transmissions. Dynaflow's non-shifting design addressed this characteristic of Buick's driveline. Torque tube rear suspension

5467-422: Was fitted with a rear pump, which meant the vehicle could be push-started (considered desirable at the time). Also, the Twin Turbine would allow engagement of low gear up to 40 mph (64 km/h), and had a shift quadrant that read P-N-D-L-R. In contrast, the Triple Turbine unit did not have a rear pump, and could not be push started. It would allow engagement of low gear up to 45 mph (72 km/h), and had

5544-506: 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

5621-541: 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

5698-639: 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

5775-548: 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

5852-466: Was now partly mechanical. This resulted in better efficiency, especially at highway speeds, and a higher level of performance and no penalty regarding the trademark smoothness. Buick also incorporated a variable-pitch stator in 1955 for greater flexibility. While these changes improved the transmission's overall performance and efficiency, the Dynaflow still was no match for other designs that utilized three element converters with automatic shifting. In 1956

5929-551: 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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