Downspeeding: The dark horse equipment trend
As far as truck equipment goes, advanced safety systems and AMTs have a relatively broad application appeal. Downspeeding, however, is heavily dependent on application—spanning numerous available ratios and axle configurations.
“We see more continuous interest in downspeeding, which has emerged as one of the leading means to improve fuel economy,” Navistar’s Gilligan said. “We are seeing ongoing interest in downspeeding regardless of whether fleets are considering 6×2 or 6×4 truck configurations based on the number of requests that we are fielding from our performance engineers.”
It’s definitely not a one-size-fits-all solution, but for fleets looking to pull the most efficiency out of their trucks as possible, it’s worth a look. And more of today’s fleets are looking.
“Fleet customers are interested in the best driveline that fits their overall needs, while delivering the best fuel efficiency and performance,” Volvo’s Moore said, highlighting Volvo’s XE powertrain packages that offer a downsped solution. “Many fleets require one driveline to work in different applications. For example, regional haul pick-up and delivery during the day, and interstate line haul at night.
“Our challenges are to keep developing downspeeding packages for greater fuel efficiency with taller rear axle gearing, while maintaining acceptable performance. Drivers need trucks that can get them onto a highway at a low stress level, while at the same time get them up a grade without backing up traffic behind them.”
As far as new ratio adoption, available ratios will depend on the rear axle manufacturer, according to Peterbilt’s Gansle.
“Ratios that give the lowest engine cruise RPMs might be used more often with an automated manual [not automatic] transmission since shifting frequency will increase and not as much driver skill is required,” he said. “It’s important to note the very lowest ratios are designed for direct drive manual transmissions [2.26, 2.39, etc.], but they won’t necessarily give you the lowest engine cruise RPM like an overdrive.”
“While downspeeding is not for everyone or every application, we’re always talking with our customers to provide the best possible set up to meet their needs,” Mack’s Russoli said. “Future challenges will come, as further development of engine operating ranges and new variations of the transmissions are developed, that will require fine tuning of rear axle ratios to match. Fortunately, this is really where an integrated powertrain shines, as the components are designed to work together.”
