There are a great many reasons automated mechanical transmissions (AMTs) and their fully automatic brethren are rapidly becoming the gearboxes of choice in the North American truck market: better fuel economy, lower maintenance, and less stress and strain for truck drivers piloting big rigs.
Yet there’s another trend at work here, and that is the need to bring more brain power to transmissions and to provide them with the ability to “think,” for lack of a better word. A thinking transmission can generate more fuel savings and may eventually help guide semi-autonomous and fully autonomous trucks to their destination.
That self-driving aspect of transmissions isn’t here yet and probably won’t be for some time, explains Sandeep Kar, global vice president for mobility at consulting firm Frost & Sullivan.
“The advanced powertrain of the future means a lot more AMTs and automatic transmissions. Why? Because semi-autonomous and fully autonomous driving will require them,” he notes.
“AMTs and automatics are optimized right now for the job they do, and they can also fit into semi-autonomous driving, right up to Level 3, with no system changes,” Kar adds. “But when you get to Level 4—where there is no driver—that will require another evolution for the transmission. However, we won’t see driverless trucks within the next 10 years or beyond; the market is just not ready for it.”
Increasing the smartness of an AMT or automatic gearbox will help fleets in many other ways, well before the need to pilot semi-autonomous trucks become a full-time reality.
“[Fleets] want to move freight from point A to point B, maximizing revenue and minimizing cost. They want to optimize performance and minimize fuel consumption, [and] an AMT or automatic helps them achieve that,” Kar emphasizes.
“And as the transmission gets smarter, the driver can then focus on more important things such as safe driving instead of what gear they are in. The transmission automatically gets the best fuel economy so neither the driver nor fleet needs to worry about it,” he says. “Making the transmission smarter also means getting more data from it, and that helps improve vehicle prognostic capability.”
Kar also notes that truck driving is a demanding job, but if you can automate the gear shifts, the effort required to do this job goes down—making the driver a “happier camper” overall.
The North American Council for Freight Efficiency (NACFE) published a report examining the potential benefits of AMTs for fleets large and small, starting with what the group calls a conservative fuel saving estimate of 1 to 3%.
Mike Roeth, NACFE executive director, notes that a 1 to 3% range is conservative because the electronic platform AMTs are built upon “opens the door” to other potential fuel savings, as the transmission is integrated with the truck’s engine, axles, and other systems.
AMT as an enabler
“One challenging point in our analysis is to look at the benefits of AMTs by themselves,” he says. “What we’re finding is that AMTs are many times an enabler for greater fuel savings, as they are integrated with the truck’s other systems. It’s like buying a smartphone to get better cell phone capability and then realizing it can do a lot more like surf the web, access email, etc.”
Such enabling benefits include improved “downspeeding” capability, topographical-based shifting, and a more finely tuned ability to coast vehicles down the road using minimal fuel without the need for more shifting-intensive work on the part of drivers.
“When you have an electronic [transmission] platform in place, its capabilities can be improved via software updates rather than physical component changes,” Roeth emphasizes. “Thus, an AMT can open the door to potential future fuel savings as well.”
According to Scott Barraclough, technology product manager for Mack Trucks, the seamless integration between Mack’s mDrive AMT and proprietary line of engines lays the groundwork for more fuel savings over time.
“The data sharing between engine and transmission ECUs (electronic control modules) is much more comprehensive,” he says. “That allows the mDrive to continuously monitor changes in grade—both up and down—as well as vehicle speed, throttle position, acceleration, torque demand, and combined vehicle weight, [so it] automatically selects the best gear for optimized fuel economy and performance for the current conditions.”
Rich Price, managing director of global products for Allison Transmission, adds that the desire for more shiftless operation offers other functionality a manual gearbox simply can’t—more launching torque and better low speed maneuverability.
From a vehicle perspective, he says automatics, such as Allison’s TC10 for Class 8 trucks, can allow for faster axle speeds, which result in further improvements in fuel economy. “That means while you’re going down the road, you are shifting in the top gear ranges automatically to maintain speed; you are not speeding up or slowing down,” Price explains. “When you start talking about more integration, you are talking about adaptive and predictive cruise control, as the transmission can control speed more accurately and more consistently than a human driver.”
Such consistency is key for AMTs and automatics. By delivering accurate and smooth shifts every time, whether a driver is at the beginning of the shift or 11 hours later, fuel economy gains are maintained over the operating cycle of a truck, says Mack’s Barraclough. “It also opens the driver pool to operators who may not be able to, or want to, operate a manual transmission,” he adds.
Allison’s Price stresses that moving to self-driving technology will require “a huge amount of refinement” for current AMTs and automatics alike.
“A lot more focus on integration will still be needed going forward; not everyone does business the same way,” he explains. “We certainly will need to tighten up, especially in the area of telematics. That is a huge part of the integration and self-driving puzzle.”
Alex Stucky, Eaton’s global product strategy manager for commercial vehicle transmissions, adds that AMT and automatic engineers today “are really good at real-time analysis of the duty cycle. We know the mass of the vehicle and the grade it’s on. That’s based on intelligent calculations.”
Looking ahead
What is only gradually becoming “known” to the transmission is the condition of the roadway a mile or two ahead.
“That’s where GPS and other mapping data come in,” Stucky says. “That is the future opportunity in terms of gear selection and neutral coasting. Staying in neutral much longer, based on the road topography ahead, means saving more fuel. The transmission is then using the ‘road profile’ to make better decisions, especially in terms of gear selection.”
For example, last year the Detroit powertrain division of Daimler Trucks North America made its intelligent powertrain management (IPM) system a standard feature for all Detroit DT12 AMTs paired with any heavy-duty Detroit engine.
The company says IPM not only helps the powertrain operate as efficiently as possible based on the truck’s momentum generated by the terrain, it integrates “preloaded terrain maps” and GPS with engine and transmission functions to know the route ahead up to one mile. That helps the D12 prevent unnecessary shifts, predictively use the engine brake, and shift gears more optimally.
Allison Athey, product marketing manager of transmissions for Volvo Trucks North America, says a similar system dubbed I-See is being deployed for the company’s proprietary I-Shift AMT.
“The I-See predictive cruise control feature will help to save fuel in hilly terrain by memorizing the topography of a route and taking advantage of a truck’s momentum,” Athey says.
The intelligence provided via I-See helps the I-Shift gearbox “learn” the topography of the road, memorizing and storing it in the transmission for use the next time the driver travels the routes. By the by, I-Shift can use I-See to store up to 4,500 different hill “maps” in its electronic brain, Athey adds.
While this may sound simple, such functionality requires a lot of development, especially when maintaining fuel economy gains or improving upon them is the goal, Eaton’s Stucky says.
“When you are looking at acceleration profiles at ground level and grade, if you are also then dealing with headwinds, you need to show that data to the transmission,” he explains.
“That requires a lot of development work and tuning to get the transmission to adapt correctly the first time,” Stucky points out. “Also, when looking at the combined powertrain, [fleets] need to realize there is a little bit of error in everything from engine torque readings to speed signals. Thus, the transmission needs to understand those errors and factor that into its operation as well.”
Cost vs. savings
The higher cost of automated manual transmissions (amts) and automatics versus that of manual gearboxes is one reason fleets remain slow to adopt them, according to two separate studies, though the growing potential for saving fuel may finally be outweighing the initial price premiums.
Frost & Sullivan conducted an extensive survey on AMTs and automatic gearboxes earlier this year and discerned the following:
◗ The premium for a medium-duty truck AMT versus a manual averages between $600 and $3,000, increasing to between $1,000 and $5,000 for heavy-duty units. Fuel savings, however, range from 3 to 10% for medium-duty trucks and 0 to 8% for heavy-duty units.
◗ The medium-duty truck premium for fully automatic transmissions averages $3,000 to $6,000, rising to between $6,000 and $10,000 for heavy-duty units. Fuel savings range from 1 to 6% and 3 to 5%, respectively.
◗ With newer dual clutch automated transmissions, such as Eaton’s Procision gearbox, the medium-duty price premium averages between $3,000 and $5,000 while the heavy-duty price premium averages between $5,000 and $10,000. Fuel savings are 3 to 5% for medium-duty trucks but as yet unknown for their heavy-duty brethren.
A Confidence Report compiled by the North American Council for Freight Efficiency (NACFE) in October last year on just AMTs alone determined that the upfront cost of AMTs ranges anywhere from $3,000 to $5,000 more compared to manual transmissions. Yet the group thinks AMTs can also deliver what it calls a “conservative” fuel saving estimate of 1 to 3% depending on their application. That 3% “top end” fuel economy improvement from AMTs should deliver $2,300 in savings per year per truck, with fuel costs pegged at 65¢ per mile with an average 120,000 mi. driven per year, notes Mike Roeth, NACFE executive director.
Roeth adds that the NACFE report analyzed the fuel saving value of AMTs placed into both long-haul and regional tractor-trailer service. It found that AMTs in long-haul on-highway operations typically obtain the lowest fuel savings, around 1%, as such operations typically involve far less shifting than regional operations in more congested urban locales.
