Take Cat’s New CT681 Truck For a Spin

TORRANCE, CA – Caterpillar is taking it slow with its Cat Truck program. In 2011 it launched the vocational-only series with the CT660 truck and tractor with a setback steer axle only. This covered the majority of applications, Cat said at the time, even though it didn’t meet the weight distribution needs of others.

Three years later, the company has filled that requirement with the CT681, a truck-only model with a forward-set steer axle and simpler front-end styling.

The 681’s “industrial” styling contrasts with the wide, brushed aluminum grille bezel and bumper trim on the 660. That simplicity is preferred by fleet operators of dumpers and concrete mixers, who will be the CT681’s main customers, according to Cat officials.

A third target is heavy snow-plow service with highway departments – appropriate for what’s shaping up to be another wicked winter. Hang a big plow on the front end and you can’t see any bling behind it anyway.

“True” front frame extensions, not bolt-ons, are available to carry pumps and other gear for various types of service.

The 681’s plain, unpretentious looks means less to keep shined and implies a promise of husky performance.

The dumper I drove certainly ran strongly on a gravelly off-road course at Cat’s demonstration center west of corporate headquarters in Peoria, Ill., and on nearby highways.

Along to answer questions was Brad Zingre, a Cat industrial sales representative who works out of Indianapolis.

I paid special attention to maneuverability  (pretty good), powertrain performance (excellent) and overall comfort (very nice).

The steer axle’s center sits 28 inches behind the front bumper. That’s the shortest in the truck-building business, we were told, so the long wheelbases needed in many bridge-formula states are easy to attain.

Minimum specified distances between axles and axle groups gain the maximum allowable weights and payloads under laws in such states. Think western “super dumps” and “bridgemaster” mixers and you get the picture.

Our test truck was neither; it was basically a 10-wheeler with a single, small-wheeled lift axle ahead of the tandem. Zingre said the Bibeau steel dump box carried 15 tons of sand. Add the truck’s tare weight of about 26,000 pounds and we were at 56,000 pounds gross, so the pusher axle stayed in the air.

A forward-set steer axle limits wheel cut left or right, especially with wide wheels and tires, so a driver has to immediately begin spinning the steering wheel in the desired direction while starting a 90-degree turn – something I had to quickly relearn.

Anticipating a right turn at the first public intersection, I had angled the truck to the right, but Zingre said no, we turn left here. I couldn’t do it in one swing, so backed up to correct.

After that I was OK. That limited turnability also requires more room on tight jobsites, something regular drivers know and take in stride.

Helping in such fore-and-aft maneuvers is an automatic transmission, specifically Cat’s own CX31 on this particular truck. It’s not a cheap option, but half the buyers of CT660s have been taking it, our hosts said.  (Cat also offers Eaton manual and UltraShift automated gearboxes, but no Allison automatics.) CX means on-highway and 31 is the diameter of its internal clutches in centimeters, by the way. It’s based on a powershift transmission developed years ago for a Cat off-road articulated dump truck.

It has six forward ratios that move a truck from a dead stop to 65 mph or more on the highway. With a 4.63 ratio in our truck’s rear differentials, 70 mph was about it.

The CX in this dumper was unfailingly smooth and positive in its shifting. Earlier CX31s I drove would occasionally thump during an up- or downshift, but not this one, and I gave it plenty of opportunities to hiccup. After making a couple of 30- to 40-mph circuits amid clouds of dust on the test course, I repeatedly stopped and started the truck on upgrades to see if I could make the torque converter slip or the drivetrain shudder. Several times I let the truck roll downgrade, forward while in Reverse and backward while in Drive, then hit the pedal, and it quickly stopped and easily started upward.

There was no hint of the bogging I have sometimes felt during initial startup with otherwise excellent Allison full automatics in competitor trucks.

The one-and-only engine available in Cat Trucks is the 12.4-liter CT13, called N13 by Navistar, which builds the engines (and the entire trucks, to Cat’s specifications). The CT13 has five ratings, from 365 to 430 hp and 1,250 to 1,550 lb-ft, all governed at 2,100 rpm. This displacement and these outputs are enough for most vocational jobs, and even off-road loggers and Michigan train operators are running the engine and happy with it, Cat people said.

Since Navistar dropped its MaxxForce 15 program, there’s been nothing bigger available, but Cat says there soon will be an announcement on a 15-liter engine. In the meantime, the 430-hp CT13 in this truck was very responsive and worked well with the autotranny in propelling us on road and trail.

In spite of the simple unchromed nose, one thing still decidedly deluxe is the big aluminum cab. Like most of the truck, it comes from the International PayStar 5000, but Cat people point out how they influenced the cab design:

  • large gauges, with a unique single-face speedometer and tachometer in the center of the panel ahead of the driver;
  • big buttons and knobs that are easy to operate with gloved fingers;
  • seals and sound-deadening insulation to keep out dust and noise;
  • filtered inlet air;
  • double window regulators for extra ruggedness;
  • attractive plastics and fabrics that seat and surround a driver;
  • cowl-mounted mirrors for a steady view of what’s behind.

I liked the cab’s look and feel, and appreciated its quietness.  With an 18,000-lb forwardset axle you can anticipate a stiff ride, and it was. There’s not enough room for long leaf springs, even if they’re parabolic in design, so the nose and cab hopped over bumps and bowed concrete out on the highway. I was fine in my air-suspended seat, but Zingre’s perch was on steel legs and he had to hang on at times. Of course, trucks like this seldom go out with a passenger, but if I were a Cat dealer and this were my demo truck, I’d install an air-ride seat over there to keep a potential customer in a buying mood.

Maybe you’re wondering why the new Cat Truck is labeled 681.

What happened to 680? It’s coming sometime next year and will also have a forward-set axle, but it’ll be a long-nose tractor, our hosts said. That’s a more premium market, so the CT680 will have more bright-metal trim available. 

Watch for it.

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