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General Motors Hydra-Matic & Ford New FWD Six-Speed Automatic Transmission Family
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 16, 2007 by SAE International in United States
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The Hydra-Matic 6T70 is General Motors first model of a new, two-variant front wheel drive (FWD) six speed automatic transmission family. The second variant is a higher capacity model, the 6T75. The transmission was co-developed with Ford Motor Company. The 6F50 is the Ford variant that aligns with the GM 6T70 transmission. Approximately eighty five percent of the hardware is shared or common between the GM and Ford transmission variants. Ford will also have a higher capacity variant the 6F55 to align with the GM 6T75. The first GM application is the Saturn Aura for the 2007 Model Year. The Ford Edge and Lincoln MKX in MY 2007 will be the first applications for the 6F50.
While the Hydra-Matic and Ford FWD six-speed family was designed with two variants in mind, the designed in modularity requires only changes to the second and third axis and case housings depending on specific torque requirements. This modular design enables a tremendous amount of part sharing. Modularity minimizes engineering resources, improves quality and reduces investment, piece cost, time to market and allows for a wide bandwidth of vehicle and engine applications. The current bandwidth of applications ranges from 3.0 L to 4.6 L engines. The planned engine torque capacity for the family ranges from 280 lb.-ft. to 301 lb.-ft. (380 Nm to 406 Nm) with flexibility for future growth.
The FWD six speed family is expected to improve both fuel economy and acceleration performance. As an example, the 6T70 is expected to improve fuel economy by as much as four percent, while improving 0-60 mph times by as much as seven percent when compared to the current four speed automatic that it replaces. This is accomplished by a wider overall ratio spread of 6.04:1 compared to the typical 4.0:1 for conventional four-speeds.
By developing the transmission jointly, General Motors and Ford Motor Company were able to reduce the engineering cost each had to invest bringing a new transmission to market. Furthermore, synergies with having more “eyes” on the engineering, helped speed the development and assure a robust product when released to the public.