So far, dual-clutch transmission (DCT) technology is only available in the award-winning Duonic gearbox available in Mitsubishi Fuso Canter class 4/5 trucks, but you'll be seeing more of it soon.
Fuso was first with a DCT in a commercial vehicle, announcing the Duonic in 2010 and putting it in production the following year for 2012-model-year trucks as standard equipment. In 2012 it won the Technological Development Award given by the Japan Society of Automotive Engineers.
Introduced to North America at the 2012 Work Truck Show, the transmission was said to be breaking ground that others would follow. "We believe the drivetrain philosophy expressed in our 2012 FE and FG models will help define the future of transport technology," the company said at the time.
Last month Eaton unveiled its own DCT, the Procision (see below), though it too aims only at medium-duty trucks for the time being. Production starts next year.
On the heavy-duty front both Volvo (the I-Shift 2) and ZF (the TraXon) have dual-clutch gearboxes up and ready, but so far only in Europe. No formal word as to their arrival on these shores has surfaced yet, but there's some scuttlebutt suggesting that the interesting modular TraXon will soon be seen in Peterbilt and/or Kenworth trucks. We do know that ZF has done the requisite engineering.
In the four-wheel world, and even in motorcycles, the dual-clutch idea is well established. High-end German cars use them routinely, but so do lesser marques like Ford and Volkswagen. In fact the first DCT in a production car came as an option in a 1983 Volkswagen Golf model, though Ford in Britain really launched the idea a few years earlier. Several Porsche racing cars used DCTs at LeMans, starting in 1983. Honda introduced a DCT option for its motorcycles in 2009.
Essentially, a DCT is two transmissions in one, with two clutches and two main shafts. Usually, one shaft resides inside the other one. Each clutch controls its own group of gears — in a six-speed, for example, one will take on the odd gears and the other gets the evens. As the truck reaches a shift, the electronics will direct the transmission to select the next gear before it's needed, at which point one clutch is opened while the other is closed, allowing the shift to be made with no torque interruption.
The result is quicker acceleration, markedly more refined shift quality, in some cases better fuel economy, and likely a happier driver.
EATON'S PROCISION
The Procision from Eaton is an all-new seven-speed dual-clutch transmission, designed from a clean sheet of digital paper. And the company claims it can deliver eight- to 10-percent better fuel economy than a similarly equipped vehicle with a torque-converter automatic. Production is scheduled to start mid-year in 2015 for North America, some time later for global markets.
It's the first DCT built for class-6 and -7 applications, though John Beering, Eaton's senior vice president and general manager, Commercial Vehicle Transmission, says the Procision was conceived for applications from class 4 through 8. He couldn't provide a timetable for when the company would produce models for those other weight classes, saying the market will decide.
Initial class-6/7 application targets are pickup-and-delivery, towing, and beverage vehicles, plus school buses.
The Procision sports electronically controlled shifting, of course, using grade, vehicle weight, and throttle-input data to provide, in the company's words, "optimal fuel efficiency and smooth, continuous delivery of torque under all shift conditions."
After spending half a day driving the Procision in several different trucks at the Eaton Proving Grounds in Marshall, Michigan, I won't argue with that word 'smooth'. Shifts were seamless, up or down, sometimes nearly imperceptible because there's no torque interruption at all.
In the first incarnation it's good for 660 lb. ft. of engine torque and gross weights of either 26,000 or 35,000 lb. (11,795 or 15,875 kg) depending on whether you want a park pawl or not. The higher GCW is allowed if you're not going to spec it with a pawl.
The top two gears are both overdrives in the transmission's first model, at 0.76 and 0.64, with fifth being direct. First gear has a 6.50 ratio with steps between 55 and 65 percent up to fifth gear. Given those wide spreads, the transmission won't do skip-shifts except sometimes from six to seven (just a 19-percent spread) or coming down from seven to five.
As with all DCTs, gear changes are made by swapping engine torque between clutches, with the next gear pre-selected every time.
The dual-clutch module is fully contained within the transmission, hydraulically controlled and oil-cooled for extended life. It’s fully sealed to eliminate contamination.
Features such as Dynamic Shifting allow the transmission to automatically switch between economy and performance shift schedules based on mass, grade, and demand at the throttle. When cruising on a highway, and depending on conditions, the transmission may 'choose' to go to neutral on the second torque path to save fuel.
Economy and performance shift tables can be adjusted to tune an overall calibration to meet any customer’s specific needs, says Eaton, adding that this calibration flexibility is the most it's ever offered. Transmission load on the engine is actively reduced when the truck is stopped, for increased fuel economy.
Two options seem likely to be popular. The adjustable 'Creep Mode' provides low-speed maneuverability in both forward and reverse. It allows controlled low-speed parking-lot and loading-dock driving without using the throttle. Forward and reverse creep speeds are independently adjustable to allow a customized lower speed in reverse.
As well, the adjustable 'Hill Helper' technology prevents roll-back or roll-forward for up to three seconds while on grades of up to eight percent, allowing for a controlled launch. I tried this six ways from Sunday, on short little hills from three to 20 percent gradient, and it works awfully well. Given the relatively low power of the Cummins B-series engines in the test trucks, there was a limit as to how well it worked on the steepest of grades — physics wins eventually — but this feature should instill confidence in drivers. That's an especially important point because many of the people piloting medium-duty trucks aren't first and foremost truck drivers, and starting off on a hill can be pretty intimidating.
These features can be turned on and off using Eaton’s ServiceRanger software.
The Procision comes standard with three power take-off (PTO) openings, also enabled via ServiceRanger software by dealerships after purchase. The hardware is always there, activated or not.
Procision transmissions use a new synthetic lubricant that reduces maintenance costs thanks to 150,000-mile lube-and-filter change intervals. The internal sump filter and electrical system do not require maintenance. Clutch life, says Eaton, should be no different than with an ordinary transmission.
The Procision's design life is 10 years/400,000 miles and it comes with a three-year/unlimited mile warranty, which covers the complete system including the dual-clutch module in commercial vehicle applications. School bus applications get a five-year/unlimited-miles warranty.
If transmission choice is a significant factor in driver recruitment and retention, it's a safe bet that DCT technology will make it even more so.
It does seem to make a major difference in driveability. The heavier the truck and the tougher the operating conditions, says Volvo, the more drivers will gain. Power-shift gear changes, where there's no interruption in power delivery, mean that it's easier to keep up with traffic, especially on tricky stretches of roads and on grades. The result will be more relaxed and possibly safer driving.
The Swedish outfit, first to produce a DCT for heavy trucks, adds that its I-Shift Dual Clutch should make a big difference when hauling moving or liquid cargo, like animal transport and tanker operations, since the seamless gear changes will prompt less movement in the cargo itself. The same will hold true with any other DCT.
It seems clear, as Fuso says, that this really is the future of drivetrain technology.
