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Kenworth T370's optional disc brakes provide outstanding directional stability. Photo: Kenworth Truck Co.

By: Paul Abelson

It's been more than a decade since Kenworth introduced its first wide-bodied aerodynamic truck, the T2000.

The company had earned its reputation with narrow-cab tractors and, back in the days of length laws, with full-width cab-over-engine trucks. The curved, aerodynamic surfaces of the T2000 improved fuel economy by up to 1 mpg, but traditionalists were unhappy with the shape.

In the decade that followed, truck architecture has been increasingly driven by emissions controls and fuel efficiency. Kenworth and sister company Peterbilt (both owned by PACCAR) made strong inroads in the medium-duty market typified by dump trucks, snow plows, stake trucks, and myriad trucks used to keep our communities functioning.

This year, both PACCAR companies introduced redesigned and re-engineered trucks, tractors, and PACCAR engines, expanding the trend to vertical integration among truck manufacturers.

When Kenworth invited me to PAC-CAR Technical Center near Mt. Vernon, Wash., to test drive their new vehicles, I jumped at the chance. Naturally, I selected a T700 — the flagship of the fleet and the full-width replacement for the T2000. But since most public works trucks are medium-duty, I also selected a T440 with an extended day cab and a straight T370 configured as a tanker. The tractors were loaded close to their rated weights.

SMOOTH RIDE: T700

For public works applications, the T700 would typically transport heavy construction equipment. My test drive was configured as a highway tractor, and loaded to 78,000 pounds. The route had a combination of sharp turns, rough and smooth blacktop and concrete roads, railroad tracks, interstate highways, and — south of Mt. Vernon on I-5 — Conway Hill, a 4% grade that ran nearly a mile.

The PACCAR MX engine had 485 hp and 1.650 pounds-foot of torque pulling through an Eaton Fuller Ultra Shift Plus with Hill Start Assist. The truck handled the grade easily, hitting the grade at 62 mph in cruise control at the bottom, and falling to 55 mph at 1,100 rpm up to the top.

An outstanding feature of the transmission is its ability to hold on a grade while the driver's foot goes from brake to accelerator. There is no roll back or forward creep when starting. The ride inside the spacious cab was almost like an SUV, with little jarring or shaking even when crossing railroad tracks. Turns were tight and precise, with excellent road feeling through the steering wheel.

I had PACCAR's smart steering wheel with cruise control switches under my left thumb and engine brake controls under my right.

The truck's sloped aerodynamic hood had smooth, direct, gentle curves from the oversized grill to the back of the cab. Aerodynamics work best when the air flow changes direction as little as possible. With its straight air flow, the T700 is one of the most aerodynamic and thus fuel-efficient trucks on the road. According to the driver information center, my miles per gallon were in the high 7s in town and low 8s on the highway.

The hood slope also contributed to excellent visibility, as did the large windows and aerodynamic mirrors.

HIGH STABILITY: T440 AND T370

The T440 is wider than most and quite comfortable inside. While my test ride was a tractor version, the truck can be configured for any application to 68,000 pounds. Multiple auxiliary axles can be specified for dump truck and concrete mixer applications.

Going up Conway Hill, grossing nearly 60,000 pounds, the T440 held 51 mph at the top. That's not too bad for a 345-hp, medium-duty engine with 1,150 pounds-foot of torque. Ride quality was almost as good as the T700, with just a bit more jar over the railroad tracks. Directional stability was excellent, with a feeling of total control.

The T370 was configured as a three-axle straight truck fitted with a tank body. The tank was empty, so performance impressions would be meaningless, but the 350-hp PACCAR PX-8 engine seemed more than adequate. The truck has a small diesel exhaust fluid (DEF) tank (9 gallons), adequate for 1,800 miles of selective catalytic reduction operation or at least two fill-ups.

This particular T370 had a 16,000-pound front axle, and air disc brakes all around. Ride was a bit harsher than the T440, with some bouncing off the more severe bumps, but directional stability was outstanding. During heavy braking, lateral stability was excellent. The disc brakes eliminated any hint of side pull, with straight, precise stops no matter how hard I braked.

In fairness, what can be said of Kenworth also applies to their Peterbilt counterparts, developed in parallel at the PACCAR Technical Center. But each brand has its subtle differences and its loyal following.

When you're in the market for trucks, don't just think of your traditional sources. These 2010s are certainly worth a look and a test drive.

— Paul Abelson (truckwriter@anet.com) is a former director of the Technology and Maintenance Council of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.