Product Evaluation: Kenworth T660

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Updated Jun 24, 2020

Driving rig was equipped with a Caterpillar C15 rated at 475 hp @ 2100 rpm and 1650 lb-ft of torque @1200 rpm.

Measuring fuel economy properly – that is, per SAE/TMC guidelines – is complicated and beyond the scope of a CCJ Product Evaluation. That said, Kenworth has introduced the Class 8 T660 Aerocab Aerodyne as its aerodynamic – hence, fuel-efficient – flagship. Ask anyone who’s running one (or several), and you be the judge. Let us know.

In any case, the T660 certainly looks the part. From its sleek front end with a steeper hood slope, restyled headlights and swoopy chassis fairings, this tractor, says KW, “advances the state of aerodynamic art.”

Technical tidbits
Our first test vehicle – we often use two, one for inspection and one for driving – with a 72-inch sleeper, was powered by an ’07 Cummins ISX with 485 hp @ 2000 rpm and 1650 lb-ft of torque @ 1200 rpm. Mated to an Eaton Fuller 10-speed AutoShift Gen3 transmission, it puts power to the ground through an Eaton Fuller 151⁄2-inch Solo clutch, and a Dana Spicer rear with 3.36 gearing. Brakes are a mix of Bendix ES 16.5×5 with Meritor drums up front, and Meritor Q+ 16.5×7 brakes and drums in the rear.

The second T660, set up for driving with a loaded trailer, was equipped with a Caterpillar C15 rated at 475 hp @ 2100 rpm and 1650 lb-ft of torque @1200 rpm. It was spec’d with an Eaton Fuller 13-speed UltraShift tranny, and a Dana Spicer 3.55 rear.

While evaluators didn’t spend as much time with this driving rig as the inspection vehicle, they were duly impressed with its on-road performance – more on that later.

Lookin’ good
During a brief walkaround, evaluators were impressed by the T660’s fit and finish, and appreciated the three-piece sheet-molded-compound hood and two-piece front Meton bumper, noting that damaged parts can be replaced without buying whole new assemblies.

The vehicle’s halogen headlights, evaluators learned, throw light four times further than previous ones, and bulbs can be replaced without tools. High-intensity, or xenon, lamps are a super-bright option.

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Several other touches caught evaluators’ immediate attention, including cowl-mounted (rather than door-mounted) mirrors to reduce mirror shake and improve sheet-metal durability; and full, rubber weatherstrips mounted to doors to reduce damage from entry/egress.

At the rear of the vehicle, the proprietary Kenworth air suspension drew praise for its trailing arms, which both locate the assembly laterally and are connected to torsion-type anti-sway bars to help keep the vehicle level in turns. The trailing-arm bushings, says KW, require no lubrication for the life of the vehicle.

Easy to live with
Maintenance-wise, the first thing evaluators noticed was the ease of opening the hood. It’s aided by thin spring cylinders, which easily could be mistaken for gas struts. Overall access is good, they judged, with most daily-check items located on the driver’s side. Given a chance to inspect mechanicals, evaluators noted carefully routed cables and hoses mounted to the frame wherever possible, reducing the chance of chaffing and unintentional damage.

The list of low-maintenance items goes on, including: a pad-mounted alternator; standard silicone hoses with constant-torque clamps; easy, underhood HVAC and windshield-wiper-motor access; and splash shields that tilt up with the hood. “I’d much rather see technicians working on an actual problem,” said Jim Bechtold, assistant chief engineer, “rather than removing parts to gain access.”

The new-for-’07 diesel particulate filter, mounted either under the vehicle or vertically behind the cab, was judged to be easy to access, although there shouldn’t be a need to do so for several hundred thousand miles, says KW.

The only thing on the evaluators’ maintenance wish list was air-hose fittings that are color-coded to match the hoses. KW says it uses industry-standard fittings, along with color-coded hoses.

Deserving special mention, said evaluators – who were anxious to try it out – is KW’s Clean Power System. It’s a factory-installed alternative to idling or motor-driven auxiliary power units, which provides climate control and 120-volt sleeper loads for up to 10 hours (a similar system is available on KW’s cousin Peterbilt trucks). It uses a “power pack” with deep-cycle batteries to do so, and they’re independent of the dedicated starting batteries. Meanwhile, a small diesel-fired heater keeps the cab and sleeper warm in cold climes, and the system can be powered and charged by shore power when available.

On the road again
“It’s like a luxury car,” said one evaluation team member of his driving experience. His opinion admittedly was influenced by the high-end Pendleton special-edition interior trim in our driving test rig.

Nonetheless, all evaluators gave high marks to instrumentation, controls, comfort, visibility, maneuverability, ride and handling. “I can’t find anything wrong with it,” added another evaluator.

With amenities like power windows and door locks, tilt-and-telescoping steering wheel, stowaway armrests and more storage space than grandma’s attic, our driving rig garnered no criticisms at the hands of evaluators.

Trust us, that doesn’t happen often.

Kenworth T660 specifications (as inspected)
Wheelbase: 228 in.
Engine: Cummins ISX, 485-hp @ 2000 rpm and 1650 lb-ft of torque @ 1200 rpm
Transmission: Eaton Fuller, 10-speed AutoShift Gen3
Clutch: Eaton Fuller, 151⁄2-inch Solo
Front axle: Dana Spicer, 12,000-lb.
Rear axle: Dana Spicer, 40,000-lb.
Brakes: Bendix ES 16.5×5 with Meritor drums front, Meritor Q+ 16.5×7 rear
Antilock: Bendix 4S/4M
Wheels: KW Stylized II, 22.5 x 8.25
Tires: Bridgestone, 295/75R22.5
Fuel tank: 100-gal., aluminum, round, x 2

The fleet operator’s opinion
CCJ Product Evaluations are not performed by CCJ editors. They are done by a team of fleet equipment managers, chosen for their experience with the type of product being evaluated. Editors report evaluators’ opinions, not their own. Comments are not attributed directly to specific evaluators to avoid the appearance of individual endorsement or criticism of products.

An evaluation is based on a driving test and design assessment (which sometimes involves some disassembly of the vehicle), followed by a discussion among the evaluators and manufacturer’s representative(s). Manufacturers are given ample opportunity to respond to any criticisms.

As always, we welcome your comments and suggestions.

The Kenworth T660 Product Evaluation Team
Chuck Cross, shop manager, USFC, Kent, Wash.; Jake Jacobson, fleet maintenance manager, Carlile Transportation Systems (Tacoma terminal), Tacoma, Wash.; and Greg Olson, owner, and Bill Haviland, operations assistant, Evergone Transportation, Federal Way, Wash.

Also, thanks to Wayne Simons, engineering manager, and Bert Kelly, district sales manager, Kenworth Truck Co., Kirkland, Wash.