Last October, Daimler Trucks North America spoke for the first time about its plans for a vertically integrated powertrain using proprietary components from Detroit Diesel Corp. The company followed through with the introduction of its Detroit axle line in January and completed the powertrain rollout by announcing its DT12 transmission at the Mid-America Trucking Show in March.
At an August press event in the rolling hills of Napa, Calif., DTNA provided a hands-on demonstration of the new Freightliner Cascadia Evolution equipped with the 2014 DD15 engine paired with the new DT12 OA 2050 automated manual transmission. Available in direct-drive and overdrive, the DT12 will be in production in May 2013. A smaller DT12 OB 1650 to be paired with the DD13 will be available later that year.
Features of the DT12 are designed to maximize fuel efficiency and improve vehicle safety and performance. The 12-speed transmission weighs in at 789 pounds (the DT12 OB 1650 weighs 670 pounds) and combines a traditional manual gearbox with high-speed computer-controlled shift and clutch actuators that select shift pattern and clutch engagement automatically.
“The ability for the transmission and engine to share information fully leverages our integrated powertrain, providing a significant advantage to the driver,” says Brad Williamson, manager, engine and component manufacturing for Daimler Trucks North America. “The shift strategy is something you can only achieve if you make both the engine and the transmission. By sharing that information, you can manage the transmission through load sensors and grade sensors to keep the fuel economy in the sweet spot and provide smooth shifting.”
One way the DT12 maximizes fuel economy is its eCoast feature that places the DD15 engine in idle while the tractor coasts down grades while maintaining vehicle momentum. As the tractor slows, the transmission seamlessly kicks back into gear to maintain the desired speed. In a 2,500-mile test run from San Diego to Gastonia, N.C., the transmission’s eCoast was engaged for 650 miles of the journey.
Another fuel-saving feature of the DT12 is Skip Shift, a feature that lets the transmission run through lower gears more quickly by skipping gears in order to achieve cruising speed sooner. Skip Shift also improves fuel economy by eliminating select shift points.
An advanced cruise control system features three levels: a low range that tops out vehicle speed at 3 mph over the set cruise speed, a medium range that increases vehicle speed by 6 mph, and a no-limit high range.
A “creep mode” simulates a torque converter to improve maneuverability at low speeds for heavy traffic, docking and parking applications. In addition, a hill start aid prevents rollback when starting from a stop on an incline.
DTNA has integrated the transmission into its Virtual Technician: When the transmission light comes on, a fault code automatically is sent to the Detroit Customer Support Center for analysis and remedy. The DT12 is backed by a five-year 750,000-mile warranty and a two-year 200,000-mile warranty on the clutch.