It's about more than just delivering consistent power, performance, and fuel economy. It's about more than just relieving truck drivers of the oft-times burdensome and tiresome task of shifting gears — especially when the road ahead is dotted with 40 traffic lights certainly not timed to the rhythm of a big rig. It's even about more than protecting the driveline from the damage caused by poor shifting habits. Today, automatic and automated transmissions are taking another critical step in their evolution — bundling all of those various benefits into packages that can be precisely tailored to specific truck applications. In doing so, the best combination of power, performance, and fuel economy are made available to the operators of everything from dump trucks and concrete mixers to over-the-road long-haul, regional and local trucks.
“We serve a variety of truck markets like construction, short-haul tractor, fire and emergency, refuse, school bus, transit bus and military — just to name a few,” says Lou Gilbert, director-North American marketing for Allison Transmission. “Each of these markets has unique needs that will continue to require specific feature content, product attributes and optimization requirements.”
To more precisely tune or optimize Allison's automatic transmissions to each of those markets requires more detailed integration with the many engines powering the trucks operating in those varied applications. “The highest level of engine/transmission integration is something we call Shift Energy Management & Low Range Torque Protection or simply SEM/LRTP,” Gilbert notes. “These features require very specific messaging between the transmission and engine to communicate engine torque and other high-level information.”
Such detailed information forms the very foundation of Allison's optimization work, he points out. “It allows [truck] OEMs to offer features like load-based shift schedules, higher horsepower and torque ratings, plus what we call ‘super economy shift schedules’ that provide the best in transmission application, durability, shift quality and fuel efficiency,” Gilbert says.
This concept is also very much in play where automated manual transmissions (AMTs) are at work, explains Shane Groner, product planning manager-North America for Eaton Commercial Vehicle Transmissions. “It's about tailoring our product offerings to the type of chassis, engine, and application of the end user,” he says. “It's about offering a wide range of ratios and software coverage to match everything from heavy haulers pulling gravel trains to concrete mixers at idle when unloading on out to flatbed and dry van operations.”
It's also about matching the precise “sweet spot” for fuel economy in each application, to pinpoint the specific shift points within a particular engine's fuel map operating in many different kinds of applications. “This is how you maximize the overall efficiency of the truck for the duties it's called upon to perform,” Groner says. “It's also how you maximize the comfort factor for the drivers in each application, giving them the performance and power they need to get that job done.”
Yet, at the end of the day, these automatic and AMT drivelines are also designed to maximize the safety envelope within the applications drivers operate their various vehicles, stresses Ed Saxman, powertrain product manager for Volvo Trucks North America.
“Say you have a driver with a heavy load going 40 mph down a grade in heavy traffic who realizes he's got a tight right turn coming up for making his delivery,” Saxman says. “Using an AMT such as Volvo's I-Shift allows that driver to keep both hands on the wheel, with both eyes and all his attention focused on the traffic around his vehicle. He's not distracted trying to figure out what gear to downshift into — or, worse, making an incorrect shift that damages the driveline and affects his operational control of the vehicle.”
The “driver just brakes and makes the turn, for the sensors and software within the I-Shift are already downshifting, based on vehicle deceleration, grade, etc.,” Saxman continues. “It'll select the right gear, preserving fuel economy and performance while preventing any damage to the driveline from a poor downshift. That's the real key here.”
Fleets themselves are proving out those attributes, both for automatic and AMT models alike. Penske Truck Leasing Co., for example, recently took delivery of more than 1,800 new International DuraStar medium-duty trucks powered by MaxxForce DT engines mated to Fuller UltraShift HV (highway value) automated transmissions manufactured by Eaton. These will serve in the company's consumer rental fleet.
The UltraShift HV is a fully automated transmission system for Class 6 and 7 vehicles with diesel engines in the 195 to 260 hp. range, capable of handling torque capacities up to 660 lbs.-ft. and loads up to 33,000 lbs. GVW.
“Being able to sync the transmission, engine and ECM [electronic control module] units together with today's technology ensures precise shifting, which in turn delivers better fuel economy and performance,” says Marc Althen, senior vice president-administration and procurement at Penske Truck Leasing. “It also enhances the driving experience. At this time, our entire consumer truck rental fleet is equipped with either fully automated or automatic transmissions while our commercial rental fleet contains about 90% automated and automatic models.”
At this point, Althen says trucks equipped with either model automatically garner higher resale value. The jury is still out on which gets the most customer acceptance and best fuel economy.
Another factor fueling the optimization evolution of automated and automatic transmissions revolves around the driver. On the one hand, fewer and fewer drivers are entering the workforce with experience on manual transmissions. On the other, veteran drivers are becoming less enthralled with manual shifting, especially as the average length of haul continues to shorten.
“Of the drivers that are available, the ability/desire to drive a manual transmission is shrinking,” says Allison's Gilbert. “If inexperienced drivers are forced to drive a manual, repairs are often required. This becomes expensive very quickly. So, customers making the transition away from manual transmissions are looking for the easiest transmission to drive that is also the most durable, because they want to reduce the repair expenses.”
THE AUTO IMPACT
He adds that a significant portion of the straight truck and vocational segments are trending toward fully automatic transmissions, a trend that may in part be the result of the automobile industry not producing many manual-equipped vehicles, ultimately reducing the opportunity for drivers to learn the concept of manual shifting.
“This could also be a contributor to the truck driver shortage, as few new drivers are familiar with manuals,” Gilbert notes. “In either case, it pushes fleet managers to explore easy-to-drive transmission options to attract and retain drivers.”
“Today, it is harder to find experienced drivers that can operate a manual transmission effectively,” adds Penske's Mark Oliver, senior vice president-maintenance for Penske Truck Leasing. “There are a number of reasons why we are … favoring more automated and automatic trucks: better fuel economy, drivers being less and less familiar with manual transmissions, and because technological advancements have proved quite exciting. In general, Penske's truck fleet is seeking to transition away from manual.”
Volvo's Saxman points out another critical factor as well: automatic and automated transmissions alike don't get tired. And even though veteran drivers shifting manually can and do outperform both models in terms of performance and fuel economy, most can't do it consistently over long stretches. “In the past, the amount of fuel savings all depended on the driver,” he explains. “That included how the driver shifted on hills, managed poor weather and bad road conditions. Now you have an AMT in place that is not only programmed to manage those conditions, but also tuned with the engine to operate in the fuel economy ‘sweet spot’ as much as possible.”
In the end, though, the biggest benefit is safety. “I-Shift keeps the driver's hands on the wheel and eyes on the road, while relieving the inexperienced driver of the challenge of selecting and shifting into the correct gear,” Saxman stresses. “The driver can always concentrate on what is happening around him in traffic…while also reducing the work and fatigue brought on by continuous shifting, especially in traffic congestion.”