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Kenworth’s T660

MOUNT VERNON, Wash. - I must admit to feeling a certain kinship towards the Kenworth T660. I was at the Mid-America Trucking Show last year when the aerodynamic highway tractor was first introduced as...





MOUNT VERNON, Wash. – I must admit to feeling a certain kinship towards the Kenworth T660. I was at the Mid-America Trucking Show last year when the aerodynamic highway tractor was first introduced as a mere prototype. Later that year, I visited Kenworth’s Chillicothe, Ohio assembly plant just in time to see the very first production T660 roll off the line, where it was welcomed into the world by a group of engineers who greeted it with the enthusiasm of so many proud papas.

So it seemed fitting I finally had the opportunity to climb behind the wheel of the latest addition to Kenworth’s stable of highway tractors. Recently, I made the trek to the PACCAR Technical Center in Mount Vernon, Wash. to test drive several of the truck maker’s most popular models – most notably, the T660.

Admittedly, I’ve always been partial to Kenworth’s T2000 when it comes to aerodynamic highway tractors. Of the four trucks I drove that particular day (the T2000, W900L, T800 and T660), I was convinced my favourite to drive would be the ‘T-Two.’ While I can appreciate the appeal of gazing out over a large, broad hood while rumbling down the highway, in on-highway scenarios driver comfort, visibility and fuel economy reign supreme.

Fortunately, each of those characteristics I so admired in the T2000 have been passed down to the T660.

The first thing you notice about the T660 is its stylish tall and narrow grille. It’s 5% larger than the grille Kenworth used on the T600 and it has been designed to assist in the cooling of the new 2007 engines. The air that passes through the grille is directed to the cooling package, improving the efficiency of the T660’s cooling system and helping cope with the increased heat generation of the ’07 powerplants.

Somehow, Kenworth engineers managed to increase grille size while also improving aerodynamics over the T600 – and for that matter, the T2000.

No component on the T660 was overlooked during the design process as engineers strived to take advantage of every opportunity to improve air flow. The sloped hood, separate aerodynamic bumper, full-length wheel-to-wheel chassis fairings, roof fairing, sun visor, air shield, sun visor marker lights, 16-inch wide side extenders and the mirrors were all designed with aerodynamics in mind. The placement of the licence plate holder even received some special attention.

Kenworth engineers also managed to make good use of air that enters the hood inlets – it is directed to the air cleaner and climate control system.

One of the exterior features that immediately caught my eyes was the new headlight design. The sleek new design is more aerodynamic, and the headlights reputedly work a lot better than previous versions. While I didn’t drive the T660 after dark, engineers say the headlights cast light further and more evenly down the road, with Halogen lamps that produce 44% more light output than conventional sealed beam lamps. They also last three times longer and when they do require replacing, this can be done without any tools.

On each of the 2008 model-year Kenworths I drove, the exhaust aftertreatment system was neatly packaged behind easily-removable side fairings. If you need to get at the diesel particulate filter (DPF), you can simply remove four bolts and the fairings pull right off.

Climbing into the T660 was easy even with a cumbersome laptop case slung over my shoulder, thanks to two wide steps and an extra wide door. Armrests that fold away behind the seats allow for easier access to the sleeper cab – in this case, a 72-inch AeroCab Flattop. The T660 I drove was powered by a Cummins ISX 450 hp engine with 1,650 ft.-lb. of torque. The transmission was an Eaton 10-speed, three-pedal AutoShift.

My route would take me from the PACCAR Technical Center along Hwy. 20 and then down I-5 which featured a lengthy uphill grade about 15 miles to the south of the Tech Center. It was just enough to give the Cummins engine a bit of a workout with the fully-loaded 53-ft trailer in tow.

The truck drove admirably – as you’d expect from a vehicle with less than a thousand miles on it. But what impressed me the most was that it was as smooth and comfortable to drive as the T2000 I had just finished driving along the same route.

The interior was quiet and vibration-free, much like the T2000. It’s the little things that add up to the smooth, quiet ride according to Kenworth engineers. For instance, the radiator tie-rods are mounted to the frame rather than the firewall to reduce vibration as well as wear and tear on the cooling system and cab.

The dash of the T660 was what you’d expect of Kenworth – clean and classy. It featured the company’s GPS system (which I fortunately did not require the assistance of on my drive). It also included a Multi-Function Highline Display that provides real-time information such as fuel-mileage and the gear you’re currently running in.

The truck was nimble enough to maneuver through the few tight corners I had to negotiate getting on and off the Interstate and like the T2000, it was easy to see what was in front of me thanks to the enormous one-piece windshield. The dash layout was intuitive and ergonomic and I felt completely relaxed driving the T660. Before long, I was enjoying the tunes on the radio and wishing I could take it just a little further – like maybe back home to Toronto. The T660 strikes a fine balance, combining a luxury car-type driving experience with the functionality and brawn required of a heavy-duty work truck. Kenworth aficionados won’t be disappointed.

None of the trucks I drove on this outing experienced a DPF regeneration while I was behind the wheel. By all accounts, I wouldn’t have noticed even if they had, save for a light on the dashboard notifying me the regeneration was occurring. DPF regens should be completely transparent to the driver. With that in mind, it’s safe to say a 2008 truck with 2007 engine, DPF and all that jazz drives no differently than its predecessors – and that’s a good thing.

Debuting on the Kenworth T660 is the company’s Clean Power system – an engine-off cab heating and cooling system that also provides 110-volt power. The system uses four dedicated deep-cycle batteries to power a thermal storage cooler found under the bunk.

Liquid inside the storage cooler is charged to freezing when the truck is in motion or connected to shore power and then cold air is pumped through the cab by a variable speed fan when the engine is turned off. If heating is required, a small diesel-fired heating unit, also mounted under the bunk, takes charge. The system can provide 10 hours of heating and cooling, allowing for a complete off-duty cycle.

The Clean Power system is available on T660s with 72-inch AeroCab sleepers.

Despite all the tinkering Kenworth engineers did to improve aerodynamics on the T660, it’s still too early to get an accurate fuel mileage comparison to previous models.

These were among the first 2008 model year tractors to roll off the assembly lines and with the added complexity presented by new fuels, new oils and a completely new aftertreatment system, comparing the T660’s fuel mileage to pre-08 model year trucks is like comparing apples to oranges.

But Kenworth officials point out Clean Power alone can result in an 8% fuel savings due to reduced idling and they’ll be conducting their own real-world fuel mileage tests in the near future to see just how the T660 stacks up against other vehicles in the Class 8 aero division.


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6 Comments » for Kenworth’s T660
  1. craig says:

    Just wondering if anyone has had the problem where the dash lights go out when you turn on headlights on the t660’s 2012 year model.The dash lights will come back on but you have to stop and shut the truck down ond restart it

  2. Trish says:

    Does anyone know how to work the armrest?

  3. Michael Gabriel says:

    2016 KW t660 is a great truck. Floats like a cloud plenty of power for a company truck. Very well balanced. Handles heavy loads very well.
    A little nose heavy but can make it work. Great job on design.

  4. R says:

    I don’t know who designed the truck but i personally feel it is the most unuser friendly truck I have ever driven a moron designed the inside one that has never drive a truck

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