General Motors Hydra-Matic 9T50 Automatic Transaxle



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Authors Abstract
General Motors Global Propulsion Systems’ first nine-speed automatic transmission makes its debut in the 2017 Chevrolet Malibu, advancing a legacy of multispeed transmissions designed to optimize efficiency, performance and refinement. The Hydra-Matic 9T50 nine-speed is paired with a Ecotech 2.0L Turbo engine in the Malibu, contributing to an EPA estimated 33 mpg highway, a three-percent increase over the 2016 Malibu with an eight-speed automatic paired to the same engine.
The 9T50 has a wider 7.6:1 overall ratio, which is the ratio between the first gear ratio and the top gear ratio, - compared to the six-speed’s 6.0:1 ratio. The 9T50 is fitted with a “deep” 4.69 first gear ratio for excellent off-the-line acceleration and a “tall” 0.62 top gear ratio for low-rpm highway cruising. That balance optimizes acceleration and fuel economy while reducing engine noise during cruising.
With nine available forward ratios, the step size between the gears is reduced providing smooth, precise upshifts and excellent refinement. Engineering features like the Selectable One Way Clutch (SOWC), step pinion gear set, and control valves integrated into the pump support allows the 9T50 to package in the same vehicle architectures as the 6T50 six speed automatic. Vehicle integration and packaging costs have been significantly reduced so interchangeability in existing vehicles will be quick and use less capital.
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Martin, T., and Hendrickson, J., "General Motors Hydra-Matic 9T50 Automatic Transaxle," SAE Technical Paper 2018-01-0391, 2018,
Additional Details
Apr 3, 2018
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Technical Paper