Caterpillar CT680 Combines Style with Smoothness

July 29, 2015

Caterpillar now has three vehicles in its line of Navistar-built Cat Trucks. That’s not a lot compared to some truck manufacturers, but Cat’s staying focused on vocational applications, including construction and trash, where its big yellow machines have been working for years. It began with the 2011 introduction of the CT660 with its setback steer axle; then last fall came the CT681, with simple “industrial” styling and a forward-set steer axle. And now there’s the CT680, also with a forward-mounted front axle, but with a longer hood and two trim levels.

Caterpillar CT680L Test Set

Tractor: 2016 Caterpillar CT680L, conventional daycab, set-forward axle 6x4, BBC 124 in., GVW 65,850 lb. (w/ lift axle), GCW 93,000 lb.
Engine: Cat CT13 (Navistar N13), 12.4 liters (758 cu. in), 475 hp @ 1,700 rpm, 1,750 lb.-ft. @ 1,000 rpm, with engine brake
Transmission: Cat CX31, torque converter 6-speed full automatic
Steer axle: 13,200-lb. Meritor MFS-13-143A on 14,000-lb. parabolic taperleaf springs, w/ Sheppard M100 hydraulic power gear
Lift axle: 13,500-lb. Watson & Chalin SL1190, steerable
Rear axles: 40,000-lb Meritor MT-40-14X-5DCR-P, 1/2-in.-thick carrier walls, w/ locking differentials and 4.63 ratio, on 40,000-lb. Hendrickson HAS-402-55 air-ride
Wheelbase: 244 in.
Brakes: Meritor S-cam drums
Tires & wheels: 11R22.5 Continental HSR2 front, HDR2 rear, on polished aluminum discs
Fifth wheel: Fontaine SL7LWB825024 air-slide
Fuel tank: 120-gal., 24-in. dia. polished aluminum
DEF tank: 9.5-gal. plastic
Trailer: 48-ft. Trail King 60SSD tri-axle steel side-dump

The last two are closely related in model numbers and axle configuration, but styling really sets them apart. The 680 offers two trim levels, one somewhat simple, like the 681, and the other sporting more bling in its nose. Cat executives announced the new truck model in mid-May at their Tinaja Hills Demonstration Center southwest of Tucson, Ariz. They explained that, as with the previous models, the 680 is available as a straight truck and tractor, and they are powered by diesels with “vocational-specific” ratings and drivetrain options. Their forward-set steer axles stretch wheelbases and add legal payload in bridge-formula states.

Execs also began answering a question many people have been asking since the original model’s intro: The 13-liter-class diesel is fine, but will there be a larger 15-liter engine? Yes, they said, and we’ll have an announcement later this year. They added that it will use the same selective catalytic reduction system for exhaust gases—equipment made by Cummins—as the current Navistar-made, Cat-branded diesel. So the bigger engine could come from one of several directions, and we’ll have to wait and see which it’ll be.

Looks are subjective, but I think this is one of the most handsome Class 8 models out there: big, bold and masculine. Styling accents set it apart from the previous two models, though there are similar lines in the hood and fenders. The CT680’s two versions are L, with a three-piece Metton composite-plastic hood, composite halogen headlights, and polished stainless steel grille bezel and chromed bumper; and LG, with a one-piece fiberglass hood, sealed-beam halogens, and painted grille-surround and black bumper for those who want a simpler appearance, like the 681’s.

For driving, Cat reps offered a pair of L-trimmed tractors, one with a loaded dump trailer and the other bobtail. I drove bobtail tractor on gravel and dirt, and it rode and handled nicely. It had an Eaton Fuller 18-speed manual whose lever and gear splitter operated smoothly and surely, even during float-shifting without the clutch, and even with barely 3,000 miles on the odometer, when I’d expect some stiffness.

The red four-axle tractor was my mount for the on-highway portion. It pulled a Trail King 48-foot steel side-dump trailer whose rear end rode on three axles. The round-bottom tub carried some big boulders that helped boost the rig’s scale weight to nearly 92,000 pounds, according to the crew. With six axles on the ground, we left the tractor’s pusher-type lift axle hanging in the air. Riding shotgun was Brad Zingre, a Cat industrial sales representative who works out of Indianapolis. He was also my guide as I test-drove the previous two models, starting with the CT660 in Ohio several years ago and then the 681 in Illinois last fall.

We agreed that this 680 tractor rode the best of the three, partly because frost-free pavement in Arizona is comparatively smooth and the steer axle was farther forward. And this time Zingre had an air-ride passenger seat, whereas he sat on a solid-mount seat in the 681. Leaving the demo center, we wound down the curving access road where I took care to keep the trailer wheels off the shoulder, then turned east on Duval Mine Road, following it down to Interstate 19. There we turned north toward Tucson. With help from strong winds blowing from the southwest, I quickly got us up to cruising speed of 65 or so mph, set the cruise control there, and enjoyed the ride.

Power under the 680’s hood came from a Navistar-built CT13 diesel, the larger of two engines currently available in the Cat Truck series (the other’s the CT11), and this one had the strongest rating of 475 horsepower and 1,750 lb.-ft. The CX31 torque-converter automatic smoothly and positively sent all that twist to the drive wheels, and, with power steering and strong air brakes, made the rig amazingly easy to operate. Steering was precise, visibility in all directions was excellent, and too soon we had to turn around to head back to our starting point.

Returning west on the mine road was more taxing because now we moved slightly upgrade for much of the way. Also, we fought against those winds. So I got on the accelerator harder; the engine pulled well and made just enough growling to be pleasurable. Cat, Navistar and others have been declaring that 12 to 13 liters of displacement is sufficient for most applications, especially when engines develop the power and torque they now do. And historically, this is the engine size found in most heavy dump trucks. However, the upcoming 15-liter diesel will help with extra-heavy hauling, and will probably last longer.

The aluminum cab certainly showed its premium status on this leg of the trip. There was some faint whistling as the air moved around the big mirrors, but that’s all, indicating the doors and windows were effectively sealed. Quietness in the cab allowed Zingre and me to converse in near-normal voice tones. The CT680’s interior is refined, comfortable and pleasing. The basic cab structure is from the International PayStar and 9900i—also premium vehicles—but interior trim pieces seem unique to Cat and have a rich look and feel.

Notable is the single big gauge that houses both the speedometer and tachometer, whose needles swing around individual arcs on the instrument’s face. It takes up less space than a separate speedo and tach, leaving room for eight good-size gauges nearby for air brake, engine condition and transmission oil temp values, and fuel and diesel-exhaust fluid levels. More gauges were on the panel to the right, along with rocker switches for lights, engine brake, cruise control, tandem diff locks, and other functions.

When we wheeled into the demo center, I went out onto the gravel roads to check the tractor’s off-pavement behavior. The big Cat hardly seemed to notice what was under its tires, even if the “viper red” paint got a little dusty. I reluctantly parked it on a blacktopped lot near the offices, but suggested we take it out to Ohio so I could avoid an impending late-night airplane ride back home. “I’ll just drop you in Indy,” I told Zingre, and he almost agreed. Maybe next time.