Dynaflow

Dynaflow was the trademarked name for a type of automatic transmission developed and built by General Motors Buick Motor Division from late 1947 to mid-1963. The Dynaflow, which was introduced for the 1948 model year only as an option on Roadmaster models, received some severe early testing in the M18 Hellcat tank destroyer, which were built in Buick's Flint, Michigan assembly plant during World War II. It was also used in the 1951 Le Sabre concept car.

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 the converter's 2.1:1 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 the time in that the driver or his/her 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."

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