Test drive: Freightliner smartly leaned on its highway tractors to develop severe-duty lineup

Updated Jun 23, 2020
The SD’s hood pivots forward easily, with all inspection points on the Cummins and Detroit engines accessible from ground level.The SD’s hood pivots forward easily, with all inspection points on the Cummins and Detroit engines accessible from ground level.

What do you do if you’re a truck maker and your over-the-road market share numbers are in the stratosphere? If you’re Freightliner, you turn your attention to the vocational truck market.

About four years ago, the company decided to update its work truck lineup to take advantage of powertrain and ergonomic upgrades found on the Cascadia. Many of these upgrades are in keeping with Freightliner’s “Real Cost of Ownership” concept to make certain that every component contributes to the customer’s bottom line.

The result was the SD series that comprises three models: a 108-inch BBC, a 114-inch BBC and a 122-inch BBC. All accept a bewildering array of bodies and allow for easy spec’ing of compressed and liquefied natural gas systems.

Freightliner’s new vocational product manager, Mark Howerton, offered me the chance to compare the 108 BBC and 114 BBC models on drives through the Texas hill country, based out of Freightliner of Austin. The 114 BBC truck was outfitted with a roll-off body and an all-Daimler powertrain: a 475-horsepower DD13 mated to the Allison 4000 RDS automatic transmission. In contrast, the 108-BBC dump truck featured a 9-liter Cummins ISL diesel with an Eaton-Fuller 10-speed manual gearbox.

Both trucks feature the SD’s bold new styling, a departure from the highly refined aerodynamic lines of Freightliner’s long-haul tractors. Howerton told me that good fuel economy remains a priority on the vocational line. But given the decidedly unaerodynamic bodies featured on these trucks, and in some cases the cargo they haul, the fuel economy emphasis targets the powertrain.

Some vocational drivers spend as many hours in the cab as long-haul drivers do, so Freightliner engineers pay particular attention to cab ergonomics as well as driver comfort and productivity. The SD cab is wide, with air-ride seats as optional equipment.

Instrument and control layout borrows heavily from the Cascadia. As a result, sight lines to all instrument clusters are excellent. The steering wheel design allows a driver to check primary gauges at a glance without ducking his head to see around the steering wheel spokes. Similarly, all switches on the center panel are within easy reach.

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Visibility is particularly critical for drivers of vocational trucks, who routinely deal with ever-shifting landscapes of obstacles, people and equipment. Freightliner engineers responded with excellent sightlines – particularly over the sloped nose – and views to the rear also are outstanding. The rearview mirror design is tough enough to take a whack from a passing wheel loader and still remain remarkably vibration-free at highway speeds.

In the rolling Texas hills, both trucks proved to be highly nimble in tight construction zones. I find Freightliner trucks to have the most automobile-like feel on the highway due to handling, visibility and sound levels. In many respects, a driver may imagine he’s behind the wheel of a Class 5 pickup.

Both powertrains performed exceedingly well on the road. The 114SD was not hauling a container, so the DD13 seemed particularly aggressive when starting from a dead stop and also when a burst of throttle was required at highway speeds. A fair amount of credit goes to the Allison 4000 RDS, a vocationally optimized automatic transmission. Working in tandem with the Detroit 13-liter engine, it provides hefty low-end torque to get heavy loads moving in rough terrain.

I found the unloaded ride to be much smoother than anticipated due to Freightliner’s proprietary TuffTrac rear suspension, which was designed to ensure a smooth ride whether the truck is loaded or not.

The 108 BBC dump was loaded fully with gravel. I wondered if the 9-liter Cummins ISL would strain under that load, but there was no need to worry; it performed seamlessly and delivered plenty of power regardless of terrain or traffic. While the preponderance of AMTs in my test drives means I’ve gotten rusty on manual shifting, the Eaton-Fuller transmission proved to be as dependable and effortless to shift as always.

Freightliner has blended serious vocational power with handling and finesse that would be right at home on a smaller vehicle. It’s a credit to the attention to detail that went into the SD’s design: tough trucks that can take a pounding without beating their drivers half to death. That’s a win-win combination on any jobsite.