The automated manual 12-speed transmission from the Detroit brand of Daimler Trucks North America rolled out in a Napa Valley, Calif., press ride ‘n drive at the beginning of August.
While it’s the newest automated transmission to the North American truck market, the mechanics of the component has been proven in overseas markets, often at far higher gross combination weights than our 80,000 pounds.
The Detroit DT12 is a three-part main transmission featuring a range-change and splitter to give 12 forward speeds and four speeds in reverse. The single countershaft and aluminum casing give it a weight advantage of 100 pounds over Freightliner’s existing offering of the Eaton Ultrashift Plus, which will remain as a second automated transmission option. The new tranny features direct or overdrive top ratios.
The integrated system boasts a number of features and some significant claimed benefits over competitive transmissions including a steering column-mounted shift stalk.. This is a convenient alternative to the visually unappealing dash-mounted shift pad, but like the pad, does not intrude into a driver’s passage to the sleeper.
In use, the transmission can be operated in automatic or manual mode. In either case, pulling the shifter up towards the wheel initiates upshift; pressing down gets a downshift. In the end of the lever is a push in switch to select auto or manual mode, or a quick touch to select economy or performance shift schedule.
The column shifter also is the selector for the engine retarder, with an off, two-, four- and six-cylinder brake application as the lever is pulled down. Forward, reverse and neutral are selected with a rotary switch embedded in the shifter. A neat feature is a neutral reminder and selector if the driver forgets to take the transmission out of a drive position while setting the brakes and keying off.
There are new features for the cruise control. One is a dash-mounted switch that allows for selection of different levels of “float” in the cruise setting. In low, it will allow speed to gain 3 mph before the cruise control applies the engine brake. On the medium setting, it allows twice this margin before application. In the highest position, it removes all interaction with the truck speed, allowing the truck to roll and take maximum advantage of downgrades.
Another feature designed to improve fuel economy is e-Coast. This senses when the truck is rolling on any kind of a downgrade and applied torque drops to zero. In this case, the transmission goes to neutral and the engine speed drops to idle. While this may be thought as a somewhat little used feature, in the recent coast-to-coast economy demonstration run by Freightliner, the demonstration truck was in e-Coast mode for 25 percent of the mileage covered, accounting for significant fuel savings.
At the other end of the performance spectrum, there is a throttle kickdown switch where a detent is provided in the throttle movement. Punching through this causes a downshift and a change to the fueling schedule so that the acceleration is akin to the transmission being in the performance mode.
In the different shift modes, the transmission will upshift at 1,400-1,450 to drop back onto peak torque at 1,000 rpm; in performance mode shift points are higher to get the engine into the higher horsepower, shifting at 1,700 rpm or more, depending on a host of conditions that the transmission recognizes like grade, throttle demand and gross vehicle weight.
With the implementation of the new automated transmission, there’s a new dash display for Cascadia in 2013 that is currently referred to as IDB4. It includes information about the gears selected as well as up and down arrows for shift advice when in manual mode. It also indicates whether the transmission is in performance or economy mode.
A lighter DT12 will be available for smaller engine offerings later in 2013.
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