BEEFED-UP SIX-SPEED TRANSMISSION MEETS HIGH-TORQUE DEMANDS OF 3.5-LITER ECOBOOST ENGINE

Ford’s 3.5-liter EcoBoost™ V-6 engine has the perfect running mate for maximum performance and fuel efficiency – a six-speed SelectShift Automatic™ transmission that’s specifically designed for the higher torque demands of the all-new twin-turbocharged, direct injection engine.

Developed from the successful 6F-50 transmission, the 6F-55 is dedicated solely to the 3.5-liter EcoBoost engine and incorporates a number of component and calibration upgrades that help guarantee every bit of torque produced by the twin-turbocharged V-6 is seamlessly transmitted, giving customers that V-8-like performance they love, as well as the fuel economy they demand.

“Adapting the 6F architecture to the EcoBoost engine demanded a close look at every component, piece of hardware, and calibration measure to ensure that this transmission could answer the needs of a higher output engine; help, not hinder, fuel economy; and meet Ford’s strict durability standards,” said Barb Samardzich, vice president, Global Powertrain Engineering.

The engine/transmission combination already is proving its muster. The 2010 Lincoln MKS, the first Ford Motor Company vehicle to offer the 3.5-liter EcoBoost V-6 engine and 6F-55 transmission package, will deliver an impressive 355 horsepower and a responsive 350 ft.-lbs. of torque, along with achieving 25 mpg on the highway. Also receiving the 3.5-liter EcoBoost V-6 engine and six-speed Select Shift Automatic transmission this summer are the 2010 Ford Flex, 2010 Lincoln MKT and 2010 Taurus SHO.

A more-robust transmission

The 3.5-liter EcoBoost engine strategically uses two small turbochargers, which spool up instantly for torque output that’s impressive – peaking earlier in the rev range than a comparable, normally aspirated engine. The turbo system does, however, run at higher temperatures.

In order to handle the elevated operating temperatures associated with a turbocharged engine and carry the higher torque produced by the 3.5-liter EcoBoost V-6, the 6F-55 incorporates a blend of hardware, material and calibration upgrades.

The transmission, for example, features wider, thicker transfer and final drive gears, improved input and output carriers. A new differential case carries the higher energy produced by the engine to deliver the performance customers expect when they accelerate. Also, the ring gear on the 6F-55 is a beefier 41.5 mm versus 31.5 mm on the 6F-50.

Final drive ratios have been adjusted and matched to gear ratios to provide optimum performance and fuel economy. The Flex boasts a final drive ratio of 3.16:1. Clutches also have been upgraded with high-energy friction materials that can handle higher loads and shift energies over the long term. In addition, clutch piston material upgrades can withstand higher operating temperatures. This, along with thicker thrust washers, and an improved heat treatment on the turbine shaft help handle the higher engine torque.

“We had to bulk up and strengthen all of the transmission’s core parts for higher duty cycles,” said David Capoccia, transmission system manager, Ford Powertrain Operations. “The thicker gears, the improved carriers, upgraded clutches are all part of a set of hardware actions that translate to superior performance and durability for the customer.”

The 6F-55’s torque converter also was optimized to improve drivability and create a more-connected feel for customers. The converter even has its own exclusive efficiency curve and design for increased strength and durability, bolstered by four lugs welded on the cover in comparison to three on the 6F-50.

Helping to improve fuel economy

The 6F-55 is bigger and stronger, but not less efficient. Several of the transmission upgrades actually help improve fuel efficiency, including:

Friction material grooves, which break up the fluid flow between the friction and separator plates and help pump fluid through the plates, have been optimized to reduce overall clutch drag losses
Moving from a six- to a nine-wave CBLR (Clutch Brake Low Reverse) spring – which aids in mechanically separating the clutch plates – provides a flow path for the fluid that reduces overall clutch drag losses
Calibration measures, such as reducing the modulated slip from 40 rpm to 20 rpm, allows less fuel to be burned to deliver the same torque to the wheels; also, locking up the torque converter in lower gears expands the operating range and provides optimum fuel efficiency
Increasing the start-to-open temperature of the bypass valve by 15 degrees, which allows the transmission to run at higher, more efficient temperatures and save fuel

The 6F-55 is produced at Ford’s Van Dyke Transmission Plant in Sterling Heights, Mich. The Van Dyke plant is one of three Ford six-speed transmission Centers of Excellence.

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About Ford Motor Company
Ford Motor Company, a global automotive industry leader based in Dearborn, Mich., manufactures or distributes automobiles across six continents. With about 205,000 employees and about 90 plants worldwide, the company's automotive brands include Ford, Lincoln, Mercury and Volvo. The company provides financial services through Ford Motor Credit Company. For more information regarding Ford's products, please visit www.ford.com.