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Test Drive: Kenworth T680

Kenworth says the company invested $400 million and more than four years bringing this truck to market.

By Jim Park, Equipment Editor

When I first heard that Kenworth’s new T680 was unveiled at the Mid-America Trucking Show, I wondered why Kenworth was already upgrading the two-year-old T700.

The T680 might resemble the T700 from a distance, but I soon learned that the T680 is anything but a rehash of the T7.

Practically everything north of the frame rails is clean-slate new. From the stamped aluminum cab to the Diamond VIT upholstery, no stone was left unturned.

At its official unveiling, Kenworth General Manager Gary Moore said the company had invested $400 million over four years bringing this truck to market. If the guided tour and the short test drive I had in Louisville are any indication, I’d say the company got its money’s worth.

The finer points

Kenworth invited a few truck writers out for an up-close-and-personal tour of the truck with Jim Bechtold, director of product planning.

The biggest news is the cab itself. A first for Kenworth, this one is made of stamped aluminum. It’s highly tooled for greater manufacturing consistency and held together with self-piercing Henrob fasteners. Kenworth enlisted the design and build expertise of Magna International, one of North America’s largest automotive suppliers, with a great deal of auto industry know-how in stamped aluminum designs.

While it may seem like a small item, Bechtold says they are quite proud of the new door design. Not only does the larger door open wider and close with less effort than past designs, its hinges are an in-swing design, rather than a traditional piano hinge design.

“The in-swing door gave us more latitude in hinge placement,” Bechtold says. “We were able to optimize the fit of the door, adding strength to the assembly and making it virtually airtight.”

In fact, the cab is fitted with pressure relief devices to make opening and closing the door physically easier – and easier on the eardrums as well.

The A-pillar is steeply raked to improve airflow over the cab, and the windshield, 50% larger than other Kenworth models, is dramatically curved to move air around the cab as well as over the top. Bechtold says the curve of the glass is as much as supplier Pilkington could put into a windshield. The glass is thicker than traditional windshield glass to minimize damage from rock strikes, etc. A new adhesive cuts replacement time to about two hours.

The integrated sleeper was designed with ease of repair in mind in areas where damage has historically been a problem, namely, the rear quarters that are subject to trailer strikes during tight backing maneuvers.

Engineers did jackknife tests on the sleeper and sought the input of body shop workers. They kept the huck fasteners in this area for ease and cost purposes. The rear side panels can be replaced without removing the roof, which saves downtime and labor cost.

Inside the cab and sleeper is where the T680 really shines. One of the more significant changes is the width of the cab. At 83 inches, it’s 10 inches wider than a T660 and about 8 inches narrower than a T700. T680 will appeal to solo drivers who like larger cabs but not necessarily the barn-like cab of the T700. There are 23 inches between the seats for easy access to the 76-inch sleeper. This truck has all the room any solo driver could ask for, and it sure wouldn’t leave team drivers wanting.

Getting to 83 inches was an interesting exercise. Engineers took a cab mock-up and literally cut it into quarters – right front, left front, right rear, and left rear – and mounted them on motorized tracks. They then invited more than 800 drivers to fit the cab sections around themselves using a hand-held controller to position the sections. The dimensions of the T680 cab reflect the preferences of that crowd of test pilots.

In a similar fashion, the drivers designed their own dash panel, right down to the gauge and switch placement.

In designing the T680’s storage cabinets, engineers visited dozens of truckstops and interviewed drivers about their storage requirements.

“Not only did we ask the obvious questions, we took an inventory of everything those drivers had on board, and then we went out and bought tool boxes, boots, oil jugs, hard hats, etc., and brought them back to the labs,” Bechtold says. “We then made it our mission to find a place to store the gear drivers carry.”

One of the results of this research was the cabinet above the doors. According to Bechtold, it easily accommodates a hard hat, one of the toughest items to store.

Another interesting innovation is the pivoting worktable located on the right-hand side of the sleeper. It swivels 270 degrees for better use of space. With the optional seat swivel feature, drivers can use it as comfortably sitting on the bed as from the passenger seat. The seat turns to face rearward, and the table swivels forward to meet the seat, creating a convenient work space.

One of the things engineers were looking to change was the traditional diamond tuck upholstery. Boy, did they get an earful from drivers.

“We thought it looked rather dated, but when we checked our order summaries, it turned out to be one of the most sought-after options,” Bechtold says. “So instead of dumping it, we redesigned it with contemporary stitching, shallower pillows and a new fabric.”

It’s a subtle change, but the new look is quite refreshing.

At the helm

Our test drive, only about 75 miles, was just enough to get a sense of how all this fresh thinking translates into a 17,950-pound freight-hauling machine.

I got into the truck at Peterson Kenworth, a dealer on the south side of Louisville, not far from the Kentucky Fairgrounds. We headed south on I-65 toward Elizabethtown, where we turned and headed back again.

The most striking thing about the T680 is the quiet. Kenworth claims in its press material that there is 40% less interior noise. Compared to what, they didn’t say, but it’s darned quiet.

Imagine driving down the highway at cruise speed in the rain, and the loudest sound in the cab is the raindrops hitting the windshield. The rain was louder than the engine noise, louder than the road noise and louder than the virtually absent wind noise.

Actually, the mixture of sounds the driver is exposed to is very nicely balanced. The low growl of the ISX engine is clearly obvious, but not intrusive. In fact, it’squite pleasant.

The other big improvement is the position of the throttle pedal. It’s still hung from the firewall, but it’s also hinged to the floor, so the driver’s heel can rest on the floor. It’s a much more natural position, and it’s infinitely more comfortable than previous designs.

The truck had an Eaton UltraShift+, so we didn’t get the full benefit of the new throttle pedal position as far as shift timing goes or the air-over-hydraulic clutch, which is very easy to depress. I had to wait for my turn in the day cab to try those. However, I will say the UltraShift+ and the ISX are speaking the same language, and the shifting algorithms are very well-tuned.

The new clutch linkage was pivotal in the redesign of the cab, Bechtold says.

“Drivers told us they wanted more room between the dash and the back wall of the cab, but that distance is determined, in a large way, by the position of the mechanical clutch linkage,” he says. “To get the feel and the action right, the various levers need to be in certain positions. We couldn’t change much using a mechanical linkage, so we opted for the air/hydraulic linkage.”

That allowed engineers to move the firewall forward and up without affecting the clutch. The other advantage to the new clutch linkage is the action. It’s the easiest-to-depress clutch I’ve ever felt outside of a Toyota, but the detents in the pedal throw were retained. It feels just like a mechanical clutch linkage, but it’s much easier to work.

The larger windshield and narrower A-pillar improve forward and lateral visibility without leaving you feeling like you’re sitting in an aquarium, and the mirror placement could not have been better. A close look reveals that, although the mounts are in the same place on the cowl, the right-hand mirror is positioned a little farther back in the driver’s line of sight for better viewing. That’s attention to detail.

Driving the truck was simply a joy. It’s easy to maneuver but very solid feeling. It smooths out the bumps and jolts, but it’s not sloppy about it, and you never lose the feeling of where the wheels are on the road.

My short drive left me wanting more, but my impression was that this truck could set ride and driver environment benchmarks for some time to come.


Cummins ISX15 485 hp at 1800 rpm, 397 hp at 2100 rpm
1650 lbs-ft at 1200 w/Intebrake
Eaton UltraShift Plus transmission, FO16E313A-MHP 13-speed
0.73:1 overdrive with Hill Start Aid feature
UltraShift Cobrahead controller integrated into dash

Front End
Dana Spicer E-1322I axle, 13,200 lbs, 3.5-in. drop
Kenworth AG130 air suspension, 13,200 lbs
Bendix air-disc brakes rated for 14,600 lbs
Dana LMS wheel hubs
Kenworth 7-spoke aluminum wheels
Michelin XZA3+ 275/80R22.5 tires
Sheppard HD94 power steering gear, 13,200 lbs

Rear End
Dana Spicer DSP41 tandem axles, 40,000 lbs, 3.42:1
Kenworth AG400L suspension 40,000-lb tandem, 52-in. spread
Bendix air disc brakes rated for 45,000 lbs
Kenworth 7-spoke alum. wheels
Michelin XDA Energy 275/80R22.5 tires

Cab Chassis
76-in. Aerodyne sleeper and cab
Dual 120-gal 24.5-in. alum. fuel tanks
High Intensity Discharge, Xenon headlamps
Driver Performance Center w/5-in. full color active matrix display
Interior trim: Diamond VIT w/woodgrain and alum. accents
Wheelbase: 229 in.
Paint: Spinnaker blue effect
Dry weight: 17,955 lbs

From the May 2012 issue of HDT

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