Tried and true

Steve Sturgess (Photos by Steve Sturgess) | March 01, 2012

A tilt/telescope steering column puts the four-spoke, switch-in-spoke steering wheel where the driver feels most comfortable and connects to a TRW THP-60 steering gear.

The sleeper is the standard 72-inch-high roof Cascadia, and it has 94 inches of standing room, a 30-inch upper and 40-inch lower bunk.

Underneath all, this Cascadia has axles by its own newly renamed Detroit division. These corporate axles are shared with other Daimler products worldwide, with the DA-F steer axle on Freightliner’s taper-leaf springs and the DA-RT drive tandem on an Airliner 40,000 air suspension. The axle ratio is a 3.42-to-1 (see “Powertrain Detail” on this page). Wheel ends are by ConMet and all-round drum brakes are by Meritor.

To meet the latest FMVSS 121 braking distance requirement, these are big brakes with 16.5-by-5 Q Plus up front and 16.5-by-8.62 Q Plus on the tandem. Since they are necessarily big to generate the required braking torque, they feature massive amounts of friction material so will likely not require any service for awhile.

The Accuride wheels carry premium tires: Goodyear G399 295/75R22.5 up front and G572 on the drives. These are Goodyear’s Fuel Max tires to meet California Air Resources Board economy requirements.

Also meeting CARB mandates is a clean-idle sticker on the side of the hood. But for those cool winter nights, a toasty Webasto AirTop heater is provided under the bunk.

On the road

The Cascadia came from Los Angeles Freightliner in Fontana, Calif. The dealership is on Valley Boulevard, which has to be one of the worst pieces of pavement anywhere. So the first surprise was the comfortable ride of the Cascadia even as it bobtailed to pick up a new Utility reefer. Other trucks can bang and crash over this road, but the Cascadia was remarkably smooth.

We picked up Interstate 10 westbound and then I-15 to the high desert. Again, the ride of the Cascadia impressed, coping with the rough concrete of this stretch of interstate admirably.

The other impressive feature was the lack of noise. Admittedly we were treading lightly on the surface streets, but there was no cab-created noise, no booming or rattling. Once on the freeway, the truck settled into a quiet cruise, showing an excellent 63 decibels, which is comparable with — or even a shade quieter than — some of its closest competitors.

Another excellent feature was the sporty shifter Freightliner has engineered for the 10-speed. It had a close gate with short throws, but it was not in the least heavy. It made life very easy, and the good throttle modulation meant little difficulty with the gears, whether clutching or float-shifting the transmission.

As with all modern truck diesels, the DD15 has excellent clutch engagement torque and needs no throttle to get the truck moving. Then almost no foot-feed is necessary to get to speed. Going through low range, 900 rpm was all that was needed. Flicking the range-change up and pulling the shift lever left and back to pick up high range, it was still not necessary to use more than 1,400 rpm to get up to freeway speed, despite this being only a 10-speed.

There are two turbos on the DD15. This is common on an American big-bore diesel where series turbocharging has become almost commonplace. The difference with the Detroit DD15, though, is that the downstream turbo provides power to the flywheel through a reduction gear. The upstream turbo provides the air for the engine by way of a charge cooler. Since the downstream turbo-compound power requires its own backpressure, the engine turbocharger needs no complex variable geometry to recirculate the exhaust. And make no mistake, even though SCR is used to scrub nitrogen oxide from the exhaust, there is still need for some exhaust gas recirculation to meet emissions requirements.

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