DEARBORN, MI -- Ford Motor Co. is accelerating the shift to six-speed automatic transmissions in many of its North American vehicles, a move expected to increase performance and fuel effi-ciency. A new rear-wheel-drive six-speed and a second-generation front-wheel-drive variant will be introduced this year, giving the automaker eight vehicles available with the advanced gearboxes compared to three a year ago. Less than 1 percent of all vehicles sold today in North America use a six-speed automatic. By 2010, Ford Motor Company expects 15 to 20 percent will have six speeds, 50 percent by 2015. Craig Renneker, executive engineer, Ford Automatic Transmission Engineering Operations, says that with its growing lineup of six speeds and continuously variable transmissions in core products, Ford is strengthening its claim as an industry leader in putting advanced transmission technology on the road. "Many of our competitors are just now thinking about six speeds while we're already on our second-generation," he said. "I think we're clearly ahead of the rest of the industry. And there will be more to come at Ford, with further refinements." The new 6R -- "R" stands for rear-wheel-drive -- automatic transmission, built at the Livonia Transmission Plant, debuts in the 2006 Ford Explorer. "We received a lot of very positive feedback on the 6R, particularly about its smooth shifting," said Renneker. "The transmission is mated to the new 3-valve 4.6-liter V-8 engine to deliver excellent fuel economy and performance." The 6R also is available in the 2006 Mercury Mountaineer and will be used in other vehicles in the future. Renneker said the 6R is the beneficiary of lessons learned from Ford's first North American six-speed automatic front-wheel-drive transmission, supplied by Aisin. It was introduced last year in the Ford Five Hundred and Mercury Montego. "Overall, we are very pleased with that transmission, but we think we can drive customer satisfaction levels even higher, so we changed the calibration strategy in all of our six-speed automatics for the 2006-model year," said Renneker. This year, the improved six-speed front-wheel-drive transmission will be available in the new Ford Fusion, Mer-cury Milan, and Lincoln Zephyr mid-size cars. Six-speed automatic transmissions provide a wider ratio span between the highest and lowest gear ratios than their four-speed counterparts, making better use of engine power to deliver torque on demand and providing a four percent to eight per-cent improvement in fuel efficiency. In the near future, the Van Dyke Plant will build a new six-speed front-wheel-drive transmission, jointly engineered by Ford and General Motors, called the "6F." Although the migration of six-speed automatics throughout the company's North American products will continue, there is no plan to use them exclusively.