Ford Motor Co. plans to more than double the number of new vehicles sold equipped with six-speed automatic transmissions in North America to 1.4 million units by the end of next year, AutoTech Daily reported.

The company estimates that six-speed systems will account for 98 percent of its automatic transmission installations in the region by 2012.

The plan, prompted by future United States fuel economy standards, is much more aggressive than an estimate two years ago when Ford projected that six-speed gearboxes would represent 15 percent of the North American market by 2010 and be equipped in half of all new models five years later.

Ford says its six-speed transmissions are 4-6 percent more fuel efficient than current four- and five-speed automatics, about as efficient as a manual transmission, thanks to wider gear spans that allow longer operation at optimal rates. A higher first gear delivers more torque when accelerating from a stop, and the deeper overdrive enables a vehicle's engine to use less energy at highway cruising speeds. Other benefits include improved shift smoothness and less noise.

To support the growth plan, Ford will roll out its new 6F35 six-speed transmission this fall. The gearbox will bow in the Ford Escape and Mercury Mariner crossover vehicles, which now have four-speed automatic transmissions. The 2009-model crossovers will geta 1-mpg fuel economy boost with the six-speed despite switching to a more powerful engine. Other early adopters of the 6F35 unit will include the 2009 Mazda Tribute SUV and two other unspecified vehicles early next year.

The 6F35 will be made at Ford’s transmission plant in Sterling Heights and will double annual output of six-speed gearboxes there to 1.3 million units. The plant already assembles the 6F50 front-wheel-drive transmission, a six-speed unit used in half a dozen Ford, Mercury and Lincoln models.

The Sterling Heights plant will serve as the company's global center of excellence for front-drive, six-speed transmissions. Ford’s Livonia plant will assume the same role for rear-wheel-drive versions. Its Sharonville, Ohio, plant will produce gears and other transmission parts for the two Michigan plants.

Last year, Ford announced plans to invest $658 million in the three plants, primarily to retool for the six-speed transmissions.