The big shift is on at Ford Motor Company (NYSE:F) , as the automaker plans to more than double the number -- to 1.4 million -- of fuel-efficient, 6-speed automatic transmissions in its North American cars and trucks by the end of 2009.

The advanced transmissions provide customers 4 to 6 percent improved fuel economy compared with typical 4- and 5-speed gearboxes, as well as better acceleration and a quieter and more refined driving experience.

"Advanced six-speed automatic transmissions are an important element in our sustainability strategy to improve fuel economy for our customers and reduce greenhouse gas emissions by 30 percent in our new vehicles by 2020," said Barb Samardzich, vice president, Ford North America Powertrain Operations. "They also deliver improved acceleration and smoother shifting, all at a great value for consumers."

By the end of 2012, 98 percent of Ford's North American automatic transmissions will be advanced 6-speed gearboxes, maintaining the automaker's position as a leader of high-performance, fuel-efficient powertrains.

Less RPM, More MPG

Ford's newest 6-speed is the 6F35, which debuts in the 2009 Ford Escape and Mercury Mariner sport-utility crossover vehicles and replaces the current 4-speed. It also will be used in the 2009 Mazda Tribute, as well as two other vehicles early next year.

For 2009, the Escape and Mariner receive more powerful engines, but even with that improved power, they also increase their fuel economy by 1 mpg thanks to the new 6F35.

Key to the new 6-speed transmissions is increased gear span compared with 4- and 5-speeds. This allows vehicle powertrains to operate at a more optimum level, depending on the particular driving situation.

"For example, a higher first gear delivers more torque when accelerating from a stop while the deeper overdrive gear enables a vehicle's engine to use less energy at highway cruising speeds, which saves gas," says Phil Yuhasz, engineering director, Transmission and Driveline Engineering. "In addition, with two more gears, a 6-speed transmission allows the engine to operate at its optimum efficiency, for a greater period of time, further boosting fuel economy."

The 6F35 is produced at Ford's Van Dyke Transmission Plant in Sterling Heights, Mich., and will double the plant's production capacity to 1.3 million units annually. Van Dyke also assembles the 6F50 front-wheel-drive transmission. Last year, 221,000 6F50 transmissions were produced for the Ford Taurus, Ford Taurus X, Ford Edge, Mercury Sable and Lincoln MKX.