Hydramatic (also known as Hydra-Matic) was an automatic transmission developed by General Motors's Oldsmobile division. Introduced for the 1940 model year, the Hydramatic was the first fully automatic mass-produced transmission developed for passenger automobile use. An automatic transmission is an automobile gearbox that can change gear ratios automatically as the car or truck moves, thus freeing the driver from having to shift gears manually. ... GM redirects here. ... The final Oldsmobile Logo, an update of the Rocket theme used in various forms since 1948, debuted in the mid-1990s until the final Olds rolled off the line in 2004. ... 1940 (MCMXL) was a leap year starting on Monday (the link is to a full 1940 calendar). ... An automobile is a wheeled vehicle that carries its own motor. ...

History

During the 1930s various automakers sought methods of reducing or eliminating the necessity of shifting gears. At the time, synchromesh gears were still a novelty (and confined to the higher gears in nearly all cases), and shifting a manual gearbox required more care and skill than most drivers cared to exert. // Events and trends A public speech by Benito Mussolini, founder of the Fascist movement The 1930s were described as an abrupt shift to more radical lifestyles, as countries were struggling to find a solution to the global depression. ... Synchromesh is the term used to describe a manual transmission in which gears are brought to the same speed during shifting by a synchronizer. ...

GM had previously experimented with the Automatic Safety Transmission, a project initiated at Cadillac division in 1934 and later developed by Buick and Oldsmobile. Oldsmobile offered the AST from 1937 to 1939; Buick, which felt the results uninspiring, offered it only in 1938. The AST was a semi-automatic transmission using planetary gears and a conventional friction clutch. Cadillac is a brand of luxury automobile, part of the General Motors corporation, produced and mostly sold in the United States; outside of North America, they have been less successful. ... 1934 (MCMXXXIV) was a common year starting on Monday (link will take you to calendar). ... Buick is a brand of automobile built in the United States, Canada, and China by General Motors Corporation. ... The final Oldsmobile Logo, an update of the Rocket theme used in various forms since 1948, debuted in the mid-1990s until the final Olds rolled off the line in 2004. ... 1937 (MCMXXXVII) was a common year starting on Friday (link will take you to calendar). ... 1939 (MCMXXXIX) was a common year starting on Sunday (link will take you to calendar). ... 1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ... Epicyclic gearing is used here to increase output speed. ... A clutch is a subcomponent of an engines transmission designed to allow engagement or disengagement of the engine to the gearbox or whatever apparatus is being driven. ...

Unsatisfied with the Automatic Safety Transmission, Oldsmobile launched a new program, headed by engineer Earl Thompson, to combine hydraulic operation of a planetary gearbox (which would allow much shifting to be automated) with a fluid coupling instead of a friction clutch, eliminating the need for de-clutching. The transmission would have four forward speeds plus reverse, providing a broad range of torque multiplication. Hydraulics is a branch of science and engineering concerned with the use of liquids to perform mechanical tasks. ... A fluid coupling is a hydraulic device used for trasmitting mechanical shaft power from a rotating driver to a rotating driven load. ... In physics, torque can be thought of informally as rotational force. Torque is commonly measured in units of newton metres; although, centiNewton Meters (cNm), Foot Pounds (Lb-Ft), Inch Pounds (Lb-In) and Inch Ounces (Oz-In) are also frequently used expressions of torque. ...

The result, dubbed "Hydra-Matic Drive," went into production in May 1939 for the 1940 model year. The first Oldsmobiles so equipped were shipped in October 1939. Advertising proclaimed it "the greatest advance since the self-starter." 1939 (MCMXXXIX) was a common year starting on Sunday (link will take you to calendar). ... 1940 (MCMXL) was a leap year starting on Monday (the link is to a full 1940 calendar). ... The model year of a product is a number used to describe approximately when a product was produced. ... Generally speaking, advertising is the promotion of goods, services, companies and ideas, usually by an identified sponsor. ...

In 1940 the Hydra-Matic added 57 dollars to the car's price, rising to 100 dollars for 1941. In 1941 it also became an option on Cadillacs for 125 dollars. Almost 200,000 had been sold by the time passenger car production was halted for wartime production in February 1942. For the movie, see 1941 (film) 1941 (MCMXLI) was a common year starting on Wednesday (the link is to a full 1941 calendar). ... Cadillac is a brand of luxury automobile, part of the General Motors corporation, produced and mostly sold in the United States; outside of North America, they have been less successful. ... German soldiers at the Battle of Stalingrad World War II was the most extensive and costly armed conflict in the history of the world, involving the great majority of the worlds nations, being fought simultaneously in several major theatres, and costing tens of millions of lives. ... This article is about the year. ...

During the war the Hydramatic (mated to a Cadillac V8 engine) was used in a variety of military vehicles, including the M5 Stuart tank and the M24 Chaffee light tank. The extensive wartime service greatly improved the postwar engineering of the transmission, which was subsequently advertised as "battle-tested." Cadillac was the first automobile maker to mass produce a V8 engine. ... The Stuart was an American light tank of World War II named after the Civil War general Jeb Stuart. ... General characteristics Length 5. ...

Starting in 1948 Hydramatic became optional for Pontiacs, although Buick and Chevrolet chose to develop their own automatic transmissions. One million Hydramatics had been sold by 1949. In the early 1950s various manufacturers that could not afford to develop an automatic bought Hydra-Matics from GM. Users included: 1948 (MCMXLVIII) was a leap year starting on Thursday (the link is to a full 1948 calendar). ... Pontiac is a marque of automobile produced by General Motors and sold in the United States, and Bobbys World from 1906 to the present. ... Chevrolet, or Chevy for short, is a brand of automobile, now a division of General Motors. ... 1949 (MCMXLIX) is a common year starting on Saturday. ... // Events and No. ...

• 1950-1956 Hudson
• 1950-1956 Nash
• 1951 Frazer
• 1951-1954 Kaiser
• 1954-1955 Willys
• 1950-1954 Lincoln

In 1952 Rolls-Royce acquired a license to produce the Hydra-Matic under license for Rolls-Royce and Bentley automobiles. It continued production through 1967. 1950 (MCML) was a common year starting on Sunday (link will take you to calendar). ... 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ... Hudson refers to: Persons named Hudson Brett Hudson (1953–), American musician, singer, and songwriter, one of the Hudson Brothers Ernie Hudson, (1945–), American actor and playwright Garth Hudson (1937–), Canadian musician George Hudson (1800–1871), English railway financier George Hudson (1867–1946), English entomologist Karl Hudson-Phillips (1933–), Trinidadian lawyer... People There have been some notable men and women whose surname is Nash: Nash, Abner (1740-1786), U.S. politician Nash, Brian (born 1963), English guitarist (Frankie Goes to Hollywood) Nash, Charles W. (1864-1948), U.S. auto entrepreneur Nash, Clarence (1904-1985), Disney voice actor Nash, Dion (born 1971... 1951 (MCMLI) was a common year starting on Monday; see its calendar. ... Frazer is the name of two places in the United States: Frazer in Montana, Frazer Township in Pennsylvania. ... 1954 (MCMLIV) was a common year starting on Friday of the Gregorian calendar. ... Kaiser is the German title meaning Emperor, derived from the Roman title of Caesar, as is the Slavic title of Tsar. ... 1955 (MCMLV) was a common year starting on Saturday of the Gregorian calendar. ... 1920 Willys-Knight advertisement Willys (pronounced WILL-iss) was the brand name used by the United States automobile company Willys-Overland Motors, best known for its production of military and civilian Jeeps, during the last century. ... Lincoln is an American luxury automobile brand, operated under the Ford Motor Company. ... 1952 (MCMLII) was a Leap year starting on Tuesday (link will take you to calendar). ... The Rolls Royce logo Rolls-Royce is a set of several companies, all deriving from the British automobile and aero-engine manufacturing company founded by Henry Royce and C.S. Rolls in 1906. ... Bentleys winged B badge and hood ornament Bentley Motors Limited is a British based manufacturer of luxury automobiles and Grand Tourers. ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar. ...

The Hydramatic underwent several revisions through 1955 before being replaced by the substantially redesigned Controlled Coupling Hydramatic (also called Jetaway) in 1956. The new transmission was substantially smoother than the original, but also more complex and expensive to produce, so in the early 1960s it was phased out in favor of the lighter Roto Hydramatic torque converter automatic and, ultimately, the Turbo-Hydramatic. 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... Roto Hydramatic (sometimes spelled Roto Hydra-Matic or Roto-Hydramatic) was an automatic transmission built by General Motors and used on some Oldsmobile and Pontiac models from 1961 to 1964. ... A torque converter is a hydraulic fluid coupling that is used to transmit power from one or more engines or motors to a driveshaft or other output shaft. ... Turbo-Hydramatic is the registered tradename of an automatic transmission developed and produced by General Motors. ...

The original Hydramatic continued to be used in light trucks and other commercial vehicles well into the 1960's. It was subsequently replaced in that role by the Turbo Hydramatic, whose simplified design was much less costly to manufacture. Despite the name, the Turbo Hydramatic (THM) was not mechanically related in any way to the original Hydramatic.

The Hydramatic was a complex design that was expensive to mass produce. Nevertheless, despite some early teething problems, it was fairly reliable and was so rugged that it was widely used in drag racing in the 1960's. It was not as smooth as some competitors (notably Buick's Dynaflow, the ultimate in slip 'n slide), but it also sacrificed less performance. It paved the way for the widespread acceptance of automatic shifting. Dynaflow was the trademark name for an automatic transmission developed and built by General Motors Buick Division from the late 1940s to the mid 1960s. ...

Hydramatic is now a trade name for GM's automatic transmission division, which produces a variety of later transmissions, the most notable of which is the Turbo-Hydramatic from the 1960s to the 1990s. A trade name, also known as a trading name or a business name, is the legal name of a business, or the name which a business trades under for commercial purposes. ... Turbo-Hydramatic is the registered tradename of an automatic transmission developed and produced by General Motors. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... The 1990s decade refers to the years from 1990 to 1999, inclusive. ...

Design

The Hydramatic used a two-element, hydrodynamic fluid coupling (not a torque converter, which has at least three elements, the pump, turbine and stator) and three planetary gearsets, providing four forward speeds plus reverse. Standard ratios were 3.82:1, 2.63:1, 1.45:1 and 1.00:1. Unlike a torque converter, which can multiply engine torque during high load periods, a fluid coupling passes torque through essentially unchanged, except for losses due to slippage. This was why the first gear ratio was so low. A torque converter is a hydraulic fluid coupling that is used to transmit power from one or more engines or motors to a driveshaft or other output shaft. ... Epicyclic gearing is used here to increase output speed. ...

Despite what was once previously stated in this article, all Hydramatics were equipped with a parking lock, which many drivers did not know how to engage (after shutting off the engine, the driver had to shift into reverse, which engaged the parking lock). Neutral and reverse were at the opposite ends of the shift quadrant, creating some danger of accidental selection of reverse.

A unique feature of the Hydramatic design was the manner in which the fluid coupling was interposed in the power flow. In modern automatics, all engine power passes through the torque converter and then on to the gear train. Unless the converter includes a clutch to lock the turbine to the pump, some slippage will always occur. This was not the case with the Hydramatic.

In first gear, power flow was through the forward planetary gear assembly (either 1.45:1 or 1.55:1 reduction, depending on the model), then the fluid coupling, followed by the rear gear assembly (2.63:1 reduction) and through the reverse gear assembly (normally locked) to the output shaft. That is, the input torus of the fluid coupling ran at a lower speed than the engine, due to the reduction of the forward gear assembly. This produced an exceptionally smooth startup because of the relatively large amount of slippage initially produced in the fluid coupling. This slippage quickly diminished as engine rpm increased. A torus. ...

When the transmission upshifted to second gear, the forward gear assembly locked and the input torus now ran at engine speed. This had the desirable effect of "tightening" the coupling and reducing slippage, but unfortunately also produced a somewhat abrupt shift. It wasn't at all uncommon for the vehicle to lurch forward during the 1-2 shift, especially when the throttle was wide open. A torus. ...

Upon shifting to third, the forward gear assembly went back into reduction and the rear gear assembly locked. Due to the manner in which the rear gear assembly was arranged, the coupling went from handling 100 percent of the engine torque to about 40 percent, with the balance being handled solely by the gear train. This greatly reduced slippage, which fact was audible by the substantial reduction that occurred in engine rpm.

Many Hydramatics did not execute the 2-3 shift very well, as the shift involved the simultaneous operation of two bands and two clutches. Accurate coordination of these components was difficult to achieve, even in new transmissions. As the seals and other elastomers aged, the hydraulic control characteristics of the unit changed and the 2-3 shift would either cause a momentary flare (runup in engine speed) or tie-up (a short period where the transmission is actually in two gears at the same time).

The shift from third to fourth gear locked the forward gear assembly, producing 1.00:1 transmission. The fluid coupling now only handled about 25 percent of the engine torque, reducing slippage to a negligible amount. The result was a remarkably efficient level of power transfer at highway speeds, something that torque converter equipped automatics could not achieve without the benefit of a converter clutch.

External links

• General Motors Powertrain Division