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LAS VEGAS, Nev. - Mack's new Granite vocational models are probably the company's most unMacklike construction trucks ever built - roomy, quiet, comfortable, smooth riding - yet almost certainly as ru...

LAS VEGAS, Nev. – Mack’s new Granite vocational models are probably the company’s most unMacklike construction trucks ever built – roomy, quiet, comfortable, smooth riding – yet almost certainly as rugged as the old guard.

There are actually two models:

Granite, for provinces and states that limit weight primarily by the axle. It will tend to be short and stout, with a standard 210-inch wheelbase, 1/4-inch-thick frame inserts and steel reinforcers at certain points, plus steel hubs and other “iron” details. An 18,000-lb front axle and 38,000-lb rear tandems are standard. The Granite debuted in June, and will eventually replace the RD and DM, but not the DMM.

Granite Bridge Formula, for jurisdictions requiring both axle limits and greater distance between axles. It is standard with a longer, 248-inch wheelbase and more aluminum in the frame and running gear. No frame inserts are offered. Also standard is a 20,000-lb front axle and 38,000-lb tandem, and it’s designed to take a 12,000-lb “booster” tag axle that is mounted with the body. Fewer wheelbases and other options are available. The Granite Bridge Formula was introduced in February, and will replace only the RD-based Mack Western Contractor.

Both models have a medium-length nose and a BBC of 108 inches. They look and drive a lot alike, and each can gross up to 75,000lb when fitted with enough auxiliary axles – usually one or two pushers on the Granite, and the drop-down booster tag on the Bridge Formula, which stretches overall distance.

At the Granite’s introduction in Las Vegas, I drove two versions: a tri-axle dump with Mack’s new T310MLR transmission, and the bright blue quad-axle dump you see here. The quad had two pushers ahead of the tandem, an 18,000-lb front axle, 38,000-lb rears, a 460-hp Mack E7 E-Tech diesel running through a Mack 18-speed transmission, and a 10/12-yard Heil steel box.

Earlier in the year and also in Las Vegas, I drove a pair of long-wheelbase Bridge Formula mixers with more modestly rated, 350-hp Mack E-Techs and LL-type 10-speed transmissions. One was a quad with a pair of pushers, and the other had just a booster tag axle that works with California’s restrictive laws.

Of course, weight laws vary here among the provinces, too, and most favor shorter chassis. This is what the Granite is designed for, so is what you’ll see the most of as you travel through Canada. However, the Granite Bridge Formula has already gone to work with western-based Cindercrete Products, it was actually the third such unit sold in all of North America.

Neither Granite is a super duty model, and any multi-axle truck over 74,000 or 75,000 pounds gross must be handled by the CL, says Steve Ginter, manager of vocational sales. Curiously, the CL was originally conceived more than a decade ago as a highway tractor, but its chassis weight came in rather heavy, and it evolved into a heavy construction and trash truck. Under the CL’s long nose is where you can put the optional Cummins Big Power diesels, either the ISX with up to 565 hp or Big Red himself, the Signature 600.

Cummins’ lightweight 8.8-liter ISL is the only other engine available in the Granites. This relatively new diesel is a stroked and toughened variant of the long-running ISC (formerly known as the C8.3), and comes rated at 310 or 330 hp. With an ISL, a Granite bare chassis is at its lightest: 13,600 pounds, Ginter says.

Though the Cummins ISL is a strong runner (I drove one not long ago in a Peterbilt dumper) and looks promising for weight-conscious operators, most customers will choose the 12-liter Mack diesel.

Fuel economy is substantially better thanks to the advanced electronics and the operating range is wide and strong. On one of those loaded mixers, I lugged the E-Tech down to 850 rpm while pulling through shallow mud, and it hung right in. Don’t try that at home, boys and girls.

Mack E-Techs make a nice sound, as you can hear the combustion that produces the power. They are a bit noisy in CLs and CHs I’ve driven, rather muffled in Vision highway tractors, and pleasing in note yet still subdued in the Granites. A mixer or dumper driver will get the sound and feel of power, but won’t have his ears assaulted.

The Granite cab has much greater leg, belly and shoulder room than the 1960s R-style cab used on the RD and DM. You can bang your right knee on appliances inside old RDs, but that won’t happen in this roomy cab.

The C-style cab’s doors are wider and taller, so getting in and out of the truck is easy. The huge windshield reveals a wide view of the world, and the steeply sloped hood lets you look closely at the pavement – or dirt – just ahead. Overall outward visibility is as good as that on the old RD, whose narrow cab puts a driver’s eyes close to the glass.

The cab’s rear corners sit on air bags, which filter out shock and vibration not already caught by the advanced chassis. The ride quality is much closer to the smoothness of a Vision than the bouncing you get from an RD or DM.

The smooth ride is nice for the driver, sure, but it also protects instruments, switches and everything else in the cab – a plus for owners.

Owners should also appreciate the Granite cab’s integrity. It’s welded up from galvanized steel, and while based on the CH/CL cab, has gotten significant reinforcements.

“To say it’s a CH cab is wrong,” says Ginter, “because we spent $17 million redesigning it for severe service. It’s the strongest cab Mack has ever built.”

Both trucks were set up to pull rather than cruise at lofty highway speeds, and both rode smoothly and quietly. Maneuvering with either was easier than their front axles’ big duplex tires would suggest.

The pushers were self-steering while rolling forward, and the axles automatically raised whenever I shifted into reverse.

Big two-face mirrors showed the way while backing. Ginter points out the mirror frames break away, popping loose if the heads should collide with something, and then easily snapping back into place. That should save a few bucks during the truck’s life.

Gauges and switches on the big instrument panel are very easy to see and use. Paul Vickner, Mack’s long-time sales chief and now company president, calls it a “mission control center.”

While you can’t blast into orbit, you can monitor what’s going on with the engine and other systems.

Proliferation of electronics on any modern truck means nobody should ever cut into wiring to grab power for lights and auxiliary systems. So the Granite includes a 21-pin BodyLink connector behind the cab that body installers can simply plug into to activate anything on their products. n

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