Ford pushes 6-speeds to boost fuel efficiency

STERLING HEIGHTS, Mich. -- Ford Motor Co. said Wednesday it plans to double the number of six-speed automatic transmissions in its models by the end of next year, increasing fuel efficiency to the point where it's equal to or better than manual gearboxes.

The company also said that 98 percent of its North American transmissions will be six speeds by the end of 2012 as it moves to meet increasing government fuel economy standards.

The computer-controlled transmissions, built at a revamped factory in Sterling Heights, give drivers a 4 percent to 6 percent gas mileage boost compared with the four- and five-speed models now in widespread use in Ford's front-wheel-drive vehicles.

Because the computer calculates when to shift gears so the engine runs at peak efficiency, they can rival the mileage of lighter manual gearboxes, said Ram Krisnaswami, a Ford powertrain engineering manager.

"Some of the efficiencies within the transmission, probably the manual will score better than the automatic. But then your driving patterns, and being able to operate in the sweet spot, let the computer do it, then the automatic scores," he said. "As we improve the internal efficiency of the transmission, the automatics approach a well-driven manual by an expert."

The new transmissions allow the car to achieve higher speeds with fewer engine revolutions per minute, making it more efficient, Ford said.