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This paper describes the creation of novel transmission mechanisms using algebraic design techniques. The objective is to create novel arrangements comprised of one or more planetary gear sets, a pair of motor-generators and several torque-transmitting mechanisms (clutches and brakes). The algebraic design procedure represents the planetary gear sets, fixed interconnections, clutches/brakes, and motor-generator sets as algebraic constraints. Appropriate subsets of constraint equations are solved to identify viable transmission mechanism designs. We have used the above design approach to create several novel candidate multi-speed transmissions as well as EVT concepts. The main benefit of the algebraic design procedure is that it allows the designer to systematically generate and assess novel designs.

The Hydra-Matic 6L80 is General Motors first model of a new, four-variant, rear wheel drive (RWD) six speed automatic transmission family. The four variants are the 6L45, 6L50, 6L80 and 6L90. The new, high performance 6L80 will debut in 2006 model year performance vehicles, including the Chevrolet Corvette C6 and new Cadillac STS-V and XLR-V. By 2007, GM expects to use the RWD six speed family in as many as 25 different car, truck and SUV models in RWD, 4WD and all-wheel drive configurations. While the Hydra-Matic RWD six-speed family was designed with four variants, the built in modularity requires only two different basic diameters of parts and “flexing” on part width (length) depending on specific torque requirements. This built in modular design enables a tremendous amount of part sharing and part scaling. Modularity minimizes engineering resources, improves investment and piece cost, speed to market and allows for a wide bandwidth of vehicle and engine applications.

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.

General Motors has developed a two-mode hybrid transmission for transverse front wheel drive vehicles. Mechanical components for this system were packaged into the basic space constraints of a conventional automatic transmission by using a space-saving arrangement of two planetary gear sets and four clutches extending through two electric motors with large internal diameters. This full-function hybrid system delivers electric propulsion for low-speed urban driving, regenerative braking, electric acceleration assist, two continuously variable engine-to-wheels speed ranges, and four fixed gear ratios. This electrically-variable transmission is based on a scalable architecture for applications ranging from small vehicles and engines to full-size vehicles with large engines and towing capacity.