Detroit Diesel brought its new DT12 to a Napa, California so trade press editors could experience, first hand, the functionality and performance of the transmission. The DT12 combines the operational ease of an automatic with the efficiency of a manual transmission, but the whole is greater than the sum of its parts. Enhanced fuel economy and safety are givens today -- to be expected -- but the DT12 comes through with incredibly smooth performance, blissful ease of use, and quite remarkable performance.
It's an automated transmission for die-hard fans of manual gearboxes.
The DT12 is a 12-speed gearbox with three gear sets and two sets of high-low range splitters. It features a 17-inch pneumatically-actuated clutch that is used on most shifts for ultra smooth engagement and disengagement. The driver interface -- can't really call it a shifter, because the ECM takes care of that -- is stalk-mounted on the right side of the steering column, and despite the range of functions it controls, it's surprisingly easy to navigate.
The stalk controls up and down shifts, three-stage engine brake engagement, forward and reverse controls, auto or manual operation and optional performance and economy operation modes.
It comes with several features drivers will appreciate; creep mode for slow maneuvering, eCoast, which allows the vehicle to 'coast' down grades with the engine at idle speed, kick-down mode for passing and rapid acceleration, and the ability to toggle rapidly between forward and reverse without applying the brake.
The DT12's creep mode simulates a torque converter to improve low speed maneuverability for parking, docking, heavy traffic and other low speed situations.
Advanced technologies include Skip Shift, which automatically skips gears, enabling the transmission to run through lower gears faster to achieve cruising speed sooner.
Brad Williamson, manager, engine and component marketing for Daimler Trucks North America, says the ability for the transmission and engine to share information fully leverages the company's integrated powertrain, providing a significant advantage to the driver.
"With its intuitive design and driver-friendly features, the DT12 is an ideal solution for all drivers," said Williamson. "It will make a poor driver better, and a good driver will still be really good."
A proprietary control module communicates with the entire powertrain, giving the transmission and engine the ability to share information and offer complimentary functions, which gives the Detroit transmission an advantage that only a proprietary powertrain can provide.
For example, the engine can limit torque to protect against driveline damage and harsh shifts, while the transmission can optimize shifts to keep the engine in the sweet spot.
Drivers will also appreciate comfort features such as helical gears and geometrical optimized gear-cut for noise reduction; pneumatic clutch and shift actuation for faster gear shifts; and a choice between eco or power-mode configuration.
On the Road
Our brief test drive revealed a level of attention to detail in the design of the transmission that is second to none. As a driver, I can say unequivocally that it does everything I'd do with a manual transmission, but it accomplishes the basic tasks more quickly and smoothly than I could hope to manage with any degree of consistency.
Particularly satisfying were the creep-mode clutch engagement, and the disengagement of clutch during a downshift. Other AMTs can be a little harsh in this task. Not the DT12.
Briefly, it was a very satisfying transmission to use, very intuitive, and it performed as well or better in many respects than anything else on the market.
Watch for a more detailed test drive in Heavy Duty Trucking magazine in coming months.
The DT12 will be available in May 2013 in the Freightliner Cascadia matched with DD15 engine. By November 2013, watch for a smaller version coupled to a DD13.