Hydramatic


Hydramatic is an automatic transmission developed by General Motors Corporation's Oldsmobile Division. The Hydramatic was the first mass-produced fully automatic transmission developed for passenger automobile use. The Hydra-Matic transmission was introduced by Oldsmobile in 1939 for the 1940 model year, one year before Cadillac.

History

During the 1930s, automakers sought to reduce or eliminate the need to shift gears. At the time, synchronized gear shifting was still a novelty, confined to higher gears in most cases, and shifting a manual gearbox required more effort than most drivers cared to exert. The exception here was Cadillac's breakthrough synchromesh fully synchronized manual transmission, designed by Cadillac engineer Earl A. Thompson and introduced in the autumn of 1928.
Cadillac, under Thompson, began working on a "shiftless" transmission in 1932, and a new department within Cadillac Engineering was created, headed by Thompson and including engineers Ernest Seaholm, Ed Cole, Owen Nacker, and Oliver Kelley. During 1934, the Cadillac transmission group had developed a step-ratio gearbox that would shift automatically under full torque. This same group of engineers was then moved into the General Motors Research Laboratory, building pilot transmission units during 1935–36 that were then handed to Oldsmobile for testing.
The Automatic Safety Transmission was a tangent outgrowth of this work. The AST was a semi-automatic transmission using planetary gears and conventional friction clutch, requiring the driver to use the clutch to shift into or out of gear, but not between the two forward gears. Oldsmobile offered the AST from 1937 to 1939, while Buick offered it only in 1938.
The HydraMatic was designed to combine the hydraulic operation of a planetary gearbox with a fluid coupling instead of a friction clutch, eliminating the need for de-clutching. The transmission would have four forward speeds plus reverse, with all acceleration provided by gearing; its fluid coupling did not multiply the engine output as a torque converter does. It incorporated a parking pawl that was engaged when the shift selector was placed in reverse with the engine off. There was no separate Park position as found with modern transmissions.
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 in the Oldsmobile Series 60 and the Oldsmobile Series 70. Oldsmobile was chosen to introduce the Hydra-Matic for two reasons: economies of scale—Oldsmobile produced more cars than Cadillac and Buick at the time, thus providing a better test base; and to protect the reputation of Cadillac and Buick in case of a market failure of the new transmission. Advertising proclaimed it "the greatest advance since the self-starter".
In 1940, the Hydra-Matic was a US$57.00 option, rising to US$100.00 the following year. It also became an option on 1941 Cadillacs for $125.00. Almost 200,000 had been sold by the time passenger car production was halted for wartime production in February 1942.
During the war, the Hydramatic 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, later advertised as "battle-tested".
Starting in 1948 Hydramatic became optional for Pontiacs, and was installed in 70% of the Division’s production that year. Buick and Chevrolet chose to develop their own automatic transmissions, called Dynaflow and Powerglide. All Oldsmobiles installed with the Hydramatic had a badge at the bottom edge of the front fender directly behind the front wheel that said "Futuramic", identifying Oldsmobile’s approach to simplified driving and the presence of an automatic transmission. V8 Oldsmobiles were automatic-only in 1949, as Oldsmobile lacked a manual gearbox that could handle the torque of the new Rocket V8 engine. .
One million Hydramatics had been sold by 1949. In the early 1950s and beyond various manufacturers without the resources to develop a proprietary automatic transmission bought Hydra-Matics from GM. Users included:
In 1952, Rolls-Royce acquired a license to produce the HydraMatic for Rolls-Royce and Bentley automobiles. It continued production until 1979.
A massive fire that destroyed GM's Hydra-Matic plant in Livonia, Michigan on August 12, 1953, left the corporation and the three divisions that used this transmission scrambling for other sources of automatic transmissions to complete that year's model year production. As a result, Oldsmobiles and Cadillacs during the downtime were assembled with Buick's Dynaflow transmission, while Pontiacs used Chevrolet's Powerglide, both two-speed torque-converter units. Non-GM makes that bought Hydra-Matics from the corporation, including Ford Motor Co.'s Lincoln division and independent automakers Hudson, Kaiser, and Nash ended up looking for other sources of automatic transmissions as well, with Lincoln using the Borg-Warner-designed Ford-O-Matic transmission, while other automakers also switched to automatics from Borg-Warner during the downtime.
About nine weeks after the Livonia fire, GM opened up a new source for Hydra-Matic production at Willow Run, Michigan. By the time the 1954 models debuted in late 1953, Hydra-Matic production had returned to normal levels and all '54 model Cadillacs, Oldsmobiles, and Pontiacs with automatic transmissions were once again equipped with Hydra-Matics.
Evolving by the pressure of industrial competition from other manufacturers such as Studebaker's three-speed lock-up torque converter co-designed by Detroit Gear, named DG 200/250, and Packard's dual-range two-speed lock-up torque converter coupled Ultramatic, GM's Hydra-Matic underwent several revisions through 1955, before being gradually replaced by the substantially redesigned Controlled-Coupling HydraMatic in 1956.
The Controlled-Coupling Hydra-Matic incorporated a secondary fluid coupling and a pair of sprag clutches in place of the former friction clutch and brake bands, shifting in part by alternately draining and filling the secondary coupling. It was a later version of GM's "dual-range Hydra-Matic", first introduced in some 1952 models. The dual range feature allowed the driver to hold the transmission in third gear until the maximum allowable upshift points, for improved performance in traffic or in mountain driving. The new, dual coupling transmission also incorporated a separate park position, falling in line with other automatic transmissions of the day.
Controlled-Coupling Hydra-Matic was substantially smoother than the original Hydra-Matic, but also more complex and expensive to produce, just as efficient as the original HydraMatic because all HydraMatic transmissions, including Roto Hydra-Matic and Tempest Torque, use the split-torque design.
In 1961, The model 375 Roto Hydramatic was produced. The Roto is a four range three speed unit. The Roto eliminated the front fluid coupling that was used in the Controlled coupling Hydramatic and the connection between the engine and transmission was made by using the small fluid coupling that is used also to control the front planetary gear set'. The Roto was adopted for all Oldsmobiles as well as Pontiac's full-sized Catalina, Ventura, and Grand Prix models, while all Cadillacs and Pontiac's Bonneville and Star Chief models retained the older four-speed Controlled-Coupling Hydra-Matic unit. Controlled Coupling HydraMatic and Roto HydraMatic both have the "Split Torque feature" whereby, in high gear, the torque is divided 40% through the fluid coupling and 60% through mechanical connection, which made these transmissions more efficient than any other automatics before the lock-up torque converter was used. Hydramatic transmissions were ultimately replaced by a new three-speed torque converter automatic transmission called Turbo-Hydramatic in 1964 and 1965, whose design was more similar in principle to the Chrysler TorqueFlite and the '51 Borg-Warner-designed Ford Cruise-O-Matic than the fluid coupling Hydra-Matic the "Turbo" replaced.
The original Hydra-Matic continued to be used in light trucks and other commercial vehicles until 1962. It was subsequently replaced in that role by Chevrolet Division's Powerglide in the GMC light truck line, and later, in 1966, with the Turbo Hydra-Matic in GMC light trucks, whose simplified design was much less costly to manufacture. Chevrolet Division's light truck line used the less-than-adequate Powerglide all through the 1960s until Turbo-Hydramatic was made standard in 1969. Cast-iron Hydra-Matic production ceased at Willow Run after the 1962 model year, and Controlled-Coupling Hydramatic ceased in early 1964, allowing retooling time for the Turbo Hydra-Matic 400, which debuted in the 1964 Cadillac models in mid-year, with Pontiac Division's Star Chief and Bonneville models being the last to use the Controlled-Coupling Hydramatic of any GM car. 1964 Turbo-Hydramatic production used a selector quadrant similar to Chevrolet's Powerglide in that there was only one "Drive" position and a "Low", although it was a true three-speed unit. This was improved upon for all 1965 models with the "D L2 L1" or "D S L" quadrant, which allowed "dual range" flexibility as did the Dual-Range Hydramatic of 1953–1955. It was this version that replaced all Roto Hydramatic and Controlled-Coupling Hydramatic models in GM cars in that year, ending twenty-four years of four-speed automatic transmission production that obviated the need for a torque converter. Despite the name, the Turbo-Hydramatic has no mechanical or design related to the original Hydra-Matic, or the Controlled-Coupling Hydramatic.
Hydra-Matic was a complex design that was expensive to produce. Despite some early problems, it was reliable and so rugged it was widely used in drag racing during the 1960s. It was not as smooth as some competitors' transmissions, but was more efficient, especially at highway speeds. The Hydra-Matic paved the way for widespread acceptance of automatic shifting.
A 3-speed light-duty version of the Turbo Hydra-Matic, called the Turbo-Hydramatic 180 was produced by GM's Hydra-Matic division from 1981 to 1998 for use in a wide variety of small cars and trucks.
Hydramatic is a trade name for GM's automatic transmission division, which produces a variety of transmissions, the most notable of which is the Turbo Hydra-Matic from the 1960s to the 1990s.