Mountain Wheels: Toughened-up GMC Sierra HD may be king of the trucks |

Mountain Wheels: Toughened-up GMC Sierra HD may be king of the trucks

2015 GMC Sierra Denali 2500HD

2015 GMC Sierra Denali 2500HD

4WD Crew Cab w/Duramax diesel

MSRP: $53,740; as tested, $63,835

Powertrain: 397-HP 6.6-liter turbodiesel V-8 engine, 6-speed Allison automatic transmission

EPA mpg figures: Not rated (though 19-plus was average)

If you wonder about the real-world comfort-to-rugged ratio of the all-new GMC Sierra heavy-duty truck line, consider the fact that I spent a total of nine hours on one drive, in what I initially planned to be a three-hour on- and off-road test session.

I’d dialed in a pretty stellar example of General Motors’ upward mobility in truck design and performance, with a name almost as large as its gigantic body. The Sierra Denali 2500HD 4WD Crew Cab, with the optional Duramax turbodiesel engine, came in at a healthy $63,835, destination charges included.

In GM’s attempts to fend off the increasingly powerful, sophisticated and occasionally overly plush, full-size offerings created by Ford, Dodge and even Toyota, the Sierra heavy-duty edition is indeed a pretty formidable entry.

You’ve got the traffic-stopping styling, with the biggest chrome grille in all of Christendom. Throw in the twin-tube Rancho shocks of my 4×4 version and it’s like you got a custom lift kit, from the factory. You’ve got a 6.6-liter V-8 diesel producing 397 horsepower and 765 foot-pounds of merciless torque, meaning you can easily haul up to 17,300 pounds of fifth-wheel trailer; a heavy-duty Allison six-speed automatic transmission also aids in mitigating the grunt. There’s even those unique, built-in corner steps on the rear bumper.

And, perhaps most (or least, to some users) important, you’ve got the Denali interior upgrade, which catapults an already roomy and comfortable cabin into Cadillac-lite territory, with comfortable leather seating and appointments — not to mention a load of entertainment and safety technologies more common on puny passenger cars, but usefully appropriated for Big Truck use.

Those include the (very helpful) buzzing Safety Seat, which warns you, via your posterior, of the success of your attempts to park this nearly 240-inch-long, 80.5-inch-wide behemoth, complete with a 6-foot-6 cargo box. There’s also forward-collision and lane-departure alerts. And a full Bose audio system, plus the touchscreen navigation system.

You do need to considerably readjust your world view to fully appreciate a vehicle of this size, especially with its stuck-out trailering mirrors and imposing mass. A back-up camera and fore-and-aft sensors, integrated with that seat system, make it possible for even newbies to put the Sierra into car-sized spaces. Out in public, you sit feet above the civilian population, and the healthy clatter and roar of the diesel under the power dome hood — this is no light-duty machine like that lovely but pedestrian Ram and Jeep 3.0-liter diesel, with an $8,845 price tag to prove it — will remind you of the power that lurks beneath.

That clatter is about the only disengaging part of the Sierra experience, as the rest of the vehicle becomes relatively intuitive once you’ve worked out exactly how much space it takes up in traffic. You can pull yourself on board with a variety of hand-holds, the seats are big and supportive and there’s so much space in the crew cab with the seats flattened to the back that you could practically slide a refrigerator box in there.

Cruise control, hill start assist and automatic grade braking will take care of some of the rigors of handling a big trailer, while the diesel exhaust braking is especially helpful in controlling downhill movement. The electronic trailer brake controls are easy to reach, high and to the left of the steering wheel, and electronic trailer sway controls are built into the StabiliTrak safety software. To cope with the load, the Sierra’s rear tires are pumped up to over 70 PSI, and can be monitored through the electronic instrument display.

I put the truck through some moderately challenging and steep gravel roads and the shift-on-the-fly 4×4 system and even a lower-speed hill descent control made all of that rather effortless; torque wins in the hill-climbing battle, and the absolutely gigantic spaces under the wheel wells mean you can get all Baja on this bad boy and still make it home.

They’ve certainly beefed up the Sierra’s looks, and in these larger HD models, it turns into a festival of ominous chrome on the grille and bumper, enough to make even the overly macho Toyota Tundra look like a lightweight.

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