In addition to the obvious convenience, Oldsmobile claimed the Hydra-matic was 10 to 15% more fuel efficient than a standard transmission. Largely due to a larger rear axle ratio than a manual transmission car. Hydra-matic cars, however, were quite thirsty in city traffic, but driving quietly on the highway could reduce consumption to 1 in 8 (12.4l/100km), not bad for a large American car of this era.  

Regardless of the problems with the early cars, such as transmission oil curdling, engine surge and the tendency for abrupt hard shifts, the Hydra-matic provided simple two-pedal control. For American drivers, who were not enamored with manual shifting from the start, the Hydra-matic was a convincing advantage, even for customers who had previously been interested in semi-automatic transmissions.  

GM's policy at the time was to give its divisions a year of exclusivity on new developments. As a result, the Hydra-matic was only offered on Oldsmobiles in 1940. Buick wanted nothing to do with the new transmission. Buick's developers called it the Hydra jerk. Cadillac did add the Hydra-matic to its list of options from 1941. Despite the high price, $100 for Oldsmobile and $125 for Cadillac, more than 40% of Oldsmobile buyers and about 30% of Cadillac buyers chose this new one. option.

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As the Hydra-matic was no longer an Oldsmobile-only project, development and production was transferred to the new Detoit Transmission Division in March 1939. The first Hydra-matic was already delivered to Oldsmobile in October. When civil vehicle production was discontinued in February 1942, this new division had already sold more than 200,000 Hydra-matics.  

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The 1942 Oldsmobile proudly announces that it is equipped with the Hydra-matic transmission. Its chrome decals show this on both sides. 45% of new Oldsmobiles are now equipped in this way. Note the matte grille. Like many 1942 models, Oldsmobile had reduced the use of chrome as well as other limited use of zinc and other strategic materials.  

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battle tested

When the production of passenger cars declined, the American auto industry adapted and switched to the production of military equipment. The conversion was supervised by William 'Big Bill' Knudsen, who was president of GM from 1937 to 1940. Obviously, GM played a major role in the war. Ironically, 25 years earlier, Cadillac founders Henry and Wilfred Leland had resigned after then-chairman Billy Durant refused to be involved in military production.  

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The main tank in 1941 was the M-3 Stuart, produced by the American Car & Foundry Co. The M3, called 'Honey' by the British  was mentioned, weighed 12.7 tons. It was powered by a 7 cylinder Continental W-670 radial engine with 262 gross horsepower. In 1942 the Stuart  service in North Africa and the Pacific battlefield with the British Army as well as the US and United States Marine Corps

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The petrol powered Continental engine was scarce, forcing Stuart to use less powerful diesel engines. At the end of 1941, Cadillac introduced a new M3 variant. The Continental engine was replaced by two standard Cadillac V8 engines with 150 hp and reinforced Hydra-matic transmissions, each driving a caterpillar track.  

The redesigned tank, now called M-5, was produced from February 1942. Due to heavier armor and other changes, the M5 weighed 2100 kg more than the M3. With the two Cadillac engines, the top speed was equal to the M3.  Around 6800 M5s were produced along with about 1800 M8 self-propelled Howitzers. She shared the chassis.  

Around 1943 it became clear that the M5 was too lightly armored for the war in Europe. In April, Cadillac began development of a larger version, which shared the powertrain of the M5 but received a larger 75mm gun designed for the B25 Mitchell bomber. The new tank, the M24 Chaffee, went into production a year later. It was deployed on the front line from November 1944. By the end of the war 3400 had been produced. Some remained in use until the late 1980s. There were even a few derivatives that shared the chassis, engines and transmission. The M19 and the M37 and M41 Howitzer tanks.

Its use during the war brought no dramatic changes to the Hydra-matic's design. It has forced GM to solve the teething problems. After the war, Cadillac and Oldsmobiles used the slogan "Battle tested" in their commercials, which was true to some extent. When civilian production was restarted in late 1945, Oldsmobile also offered a number of modified automatic cars, especially for disabled veterans.

Hydra-matic is becoming commonplace

The Hydra-matic really took off during the post-war boom. By 1947, GM had already produced the 500,000th Hydra-matic.

Buick had a special drivetrain connected directly to the rear axle. Any movement of the Hydra-matic during gear changes would be felt throughout the car. This wouldn't go hand in hand with the smooth handling of a Buick. The other brands did not suffer from this because all movements were absorbed by the rear springs and by the universal joints. Chevrolet still didn't like it either and opted for the Powerglide, actually a simplified version of the Dyna-flow.  

Pontiac embraced the Hydra-matic from 1948. It was extremely popular despite its high price. Hydra-matic cost $158.50 at Pontiac and $174.25 at Cadillac. 78% of Pontiac buyers bought it and 95% of Cadillac buyers.  

In 1949 it turned out that being able to supply an automatic transmission was a great advantage, in fact, if you could not supply an automatic transmission it was a shortcoming. It didn't bother anyone that the Hydra-matic was not the smoothest and most economical, nor was it worth much in terms of performance. There were plenty of critics, but American car buyers accepted the negatives as long as they didn't have to shift gears.

Other manufacturers were soon forced to follow GM's path. Ford and Studebaker teamed up with Borg-Warner to develop a three-speed torque converter transmission. Packard introduced its own Ultramatic in May 1949. Chevrolet launched its first Powerglide in late 1949 for the 1950 model year. 

Cadillac was the first to provide the Hydra-Matic standard on the Series 60 and 62 in 1950.  

The Detroit Transmission Division built the 1,000,000th Hydra-matic in 1949. Dissatisfied with that volume, GM began signing contracts to supply the transmission to manufacturers who could not afford to develop their own automatic transmission. The first customer was Nash in 1950, then Hudson and Kaiser-Frazer in 1951 and Willys Aeros in 1954, and, oddly enough, Lincoln as early as 1949. In 1953 GMCs were also equipped with Hydra-matic and in 1954 Chevrolet trucks. Although Ford and Mercury had their Borg-Warner developed Ford-O-Matic / Merc-O-Matic, it was not suitable for the larger Lincoln engines with higher power. Most made no effort to hide the name and thus the GM origin, they were happy with the reputation and name recognition of the Hydra-matic.

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Dual-Range Hydra-matic

The Hydra-matic went through a variety of minor changes throughout its life, the biggest coming in 1952. The 'Dual-Range' Hydra-matic was developed by engineer Kenneth Gage. There were now two shift patterns of which the second pattern, depending on the brand, 
D3, D4 or S (Super) was called. Pontiac used two characters to the left and right of "Dr." Soon the names 'drive left' and 'drive right' were used. In drive right, the car would not come out of third gear until the car reached 72 mph / 115 km/h, just like at full throttle. Low was used to keep the automatic transmission no higher than 2nd gear until about 48 mph / 77 kph. Neither drive right nor low changed the maximum speed per gear, but it did provide great flexibility, especially in hilly terrain.

This 1952 Pontiac (see left photo) has the new Dual-Range Hydra-matic with two 'Dr' ranges. Oldsmobile called it D and S while other manufacturers commonly referred to it as D4 and D3. There is no Park stand yet and Reverse is still after Low. The latter eventually became the subject of a safety-related controversy in 1961.  

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Oscar Banker (patent holder of many vending machine related inventions and friend of one of the SAE board members) was mentioned in the book 'Unsafe at any speed'  from Ralph closer. It was further mentioned that at an SAE presentation for the new Roto Hydra-matic, Banker asked why the NDLR shift pattern was still being maintained. Later, Banker wrote a letter to GM's head, Jack Gordon, explaining that it was dangerous and easy to reverse.  was able to shift gears while the vehicle was still in motion. 

GM replied that the shift pattern facilitates rocking the car when stuck in snow or mud. It was also indicated that millions of Americans were already used to the current order. Partly under pressure from Banker and other engineers, the federal General Accounting Office then pushed for standardization of the PRNDL shifting pattern for federal fleets. GM eventually agreed and applied the PRNDL pattern to all of its transmissions from the 1966 model year.
 

Hydra-matic production was interrupted by a catastrophic fire in August 1953, which destroyed the entire factory. It was one of the worst industrial disasters of its time with 6 deaths and $80 million in damage. To replace the factory, GM leased the Willow Run factory from Kaiser. This former bomber factory, which Kaiser acquired in 1945, had been out of service since June 1953 after Kaiser moved to Toledo, Ohio through the merger with Willys-Overland. The factory was modified in September. In November, GM bought the plant for $26 million. While Willow Run was being re-equipped, customers had to temporarily use a different transmission. Dynaflow for Oldsmobile and Cadillac, Powerglide for Pontiac. Borg Warner was called in for the non-GM brands. Deliveries resumed at the start of the 1954 model year.

By this time, the end of the original Hydra-matic was in sight. Customers were no longer so tolerant of the rough shifting while the nascent horsepower race would exceed the buckets' maximum capacity. In 1940, only a few cars had a power that exceeded 165 hp. For example, in model year 1955, the most powerful Cadillac had 270 hp. In 1952 Detroit Transmission began development of the thoroughly redesigned Hydra-matic which debuted in 1956.

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In 1956 the Hydra Matic was completely redesigned so that all but one shifting (2nd to 3rd) was done by emptying and filling a second fluid clutch, eliminating the entire front clutch. All tires that worked with torque were eliminated, so no tire adjustments were necessary or possible. There was now only one friction circuit. The effect of this was a first to second gear sliding in before you noticed (still a very short gear due to the lack of a torque converter) and second to third with conventional clutches that was slightly better than the old Hydra-Matic, and a third to fourth that happened as quickly and as smoothly as pouring cold honey on your cornbread. Efficient? Barely. Slippery? Like a baby's ass.

The introduction of the "controlled coupling Hydra-Matic" in 1956 did not go so well. A lot of updates were needed. Most of these transmissions eventually came back to dealers for new front clutch covers, gaskets, and reverse cone clutches. By 1958 all issues had been eliminated. But by 1958, the Hydra Matic had competition. Chrysler's Torqueflight, released in mid-1956, was then considered a superior automatic. Ford's CruiseOmatic was a simpler version of the Torquelight. Studebaker used a similar Borg warner unit, and the Dynaflow, while not a model of efficiency, was still a pleasure to use in a large Buick. Released in 1964 in Buick and Cadillac cars, the THM 400 (Turbo Hydra-Matic) was an almost complete copy of the Chrysler design, as the 'Flush N Fill' Hydra-Matic was very outdated by then. .

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7,000,000 Hydra-Matics

Oldsmobile president Charles McCuen, without whose enthusiasm the Hydra-matic could not thrive, was promoted to vice president of Corporate Engineering in August 1940. In 1947, he replaced Charles "Boss Kett" Kettering as head of GM's development division. McCuen retired in 1955 after a near-fatal crash involving a turbine prototype at GM's Milford proving ground. He passed away in 1975.

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Earl Thompson probably left GM in the 1940s. He then started his own company:  'Earl A. Thompson Manufacturing Co.' in Ferndale, Michigan. Oliver K. Kelly succeeded him as head of GM's Transmission Development Group. In 1963, Thompson and his team received the "Elmer A. Sperry Award" for their work on the Hydra-matic. Thompson died in April 1967, aged 75.

Total production of the original Hydra-matic reached over 7,000,000 units. Most civilian customers switched to other transmissions in the late 1950s. Rolls-Royce built a modest number of 'Dual-Range' Hydra-matics for the Phantom V and VI up to and including 1978.

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The Hydra-matic's influence far outweighed the number produced. It was not the first automatic, but it was the first successful fully automatic transmission that set the standard for powertrain development for decades to come.

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