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.
Dynaflow, which was introduced for the 1948 model year, used a five-element torque converter (with two turbines and two stators, and a planetary gearset, providing two forward speeds plus reverse. In normal driving, Dynaflow started in high gear (direct drive), using the converter for torque multiplication. Low gear could be manually engaged and held up to approximately 60 mph (96 km/h), improving acceleration, but the transmission would not automatically upshift to high gear.
Despite its smooth shifting capability, Dynaflow developed a reputation for being slow when compared to Oldsmobile's Hydramatic and Chrysler's TorqueFlite. Dynaflow was also an inefficient transmission by virture of its initial design. In 1953 Buick redesigned Dynaflow as the Twin Turbine Dynaflow, incorporating two turbines but only a single stator, which resulted in a higher level of performance and greater efficiency of transmitted energy. Buick also incorporated variable-pitch stators in 1955 for improved flexibility.
Dynaflow was discontinued in favor of the much more efficient Super Turbine 300 two-speed automatic and three-speed Turbo-Hydramatic (which Buick dubbed "Super Turbine 400") starting in 1964.