GMC has always been about "Professional Grade" trucks, but the Denali trim level takes it up a notch or two -- it's the package for people who work hard but like to do it in style, too. Now, the folks in the big trucks will get their own pampering as GMC reveals the new 2011 GMC Sierra Denali Heavy Duty.

The Sierra Denali HD marks the first time the luxurious Denali trim has been offered on GMC's toughest trucks. Specific to the Denali package is a four-bar grille with a chrome surround, chrome accents on the doors and door handles, body-color bumpers and new 18- and 20-inch polished forged aluminum wheels. Inside, the Denali package features a Bose audio system, power-adjustable pedals, 12-way power seats and brushed aluminum trim. A heated steering wheel and heated and cooled seats are optional.

Beyond the Denali package, which will only be offered on the Sierra 2500 Crew Cab Standard Box model, those who look closely may notice a few other subtle enhancements to the 2011 Sierra's appearance. Most notable is the enhanced hood with its big louvers and powertrain badges, along with new 17-, 18- and 20-inch wheel options. Non-Denali trucks also get a new three-bar grille and a full-width chrome front bumper.

So far, you may be wondering what the big deal is. Leather and chrome packages don't mean much on work trucks, so you'll be happy to know all the money GMC didn't spend on aesthetic upgrades was directed toward upgrading the Sierra's chassis and powertrain. The result is the same 20,000-pound maximum towing capacity with a fifth-wheel trailer as the Silverado HD, as well as the same 16,000-pound maximum towing capacity with a traditional hitch and the same 6,335-pound maximum payload capacity. Unfortunately for GMC and Chevy fans, that's a little short of the specs for the new Ford F-Series Super Duty, though not by much.

Making it all possible is the latest version of the 6.6-liter Duramax turbodiesel V-8, which has been reworked internally to increase strength and improve efficiency. GMC promises that the new mill will put out "significantly" more power than the current engine, which churns out 365 hp and 660 lb-ft of torque, and reduces NOx emissions by 63 percent. If you don't need that much twist, there's always the 6.0L Vortec gasoline V-8, which is mostly unchanged save for a new camshaft that increases torque at low RPM. GMC has not yet announced horsepower or torque numbers for either engine.

Any way you cut it though, the diesel is the star of the show. Internally, the Duramax has seen its oiling system upgraded substantially and the engine can now run on B20 biodiesel without any modification. GMC says the improvements are good for an 11% increase in highway fuel economy and a range of 680 miles thanks to its massive 36-gallon fuel tank. A urea solution injected into the exhaust stream from a 5.3-gallon tank cleans up the emissions and will reportedly last 5,000 miles between fill-ups. A new diesel particulate filter now lasts for 700 miles between regenerations, a full 300 miles longer than the outgoing truck.

Helping to smooth out the power delivery and engine braking is the latest Allison 1000 six-speed automatic transmission. Allison has gone through the box and wrung out every last bit of mechanical efficiency, all while beefing it up to handle the extra torque of the upgraded diesel motor. GMC boasts that the transmission has been specifically built to match either the gasoline or diesel engine for maximum efficiency and ideal gearing. Those sticking with gasoline will get an upgraded 6L90 six-speed automatic transmission, an upgrade from the 6L80 found on current models. The transmission controller, meanwhile, has been reprogrammed to work with a new exhaust brake on diesel models to keep braking as smooth and controlled as possible.

That's right, exhaust brake. Like the system that debuted on the Ram Heavy Duty, when activated the system increases exhaust backpressure and uses the diesel's high compression to slow the truck down. It isn't simply an on-off feature, either -- the system varies the engine braking depending on conditions to help slow the vehicle smoothly. When used with the cruise control, it can maintain the truck's speed down a grade without the driver having to step on the brakes, deactivating the cruise control.

Other features include a class-leading 250 lb-ft of torque available to the PTO, a Tow/Haul mode for better control and transmission safety, a cab warm-up feature that can increase the load on the engine on cold mornings to get the heater warmed up faster and manual shifting control. Gross Vehicle Weight Rating increases to 13,000 pounds and the Gross Combined Weight Rating jumps to 27,500 pounds while the Front Axle Weight Rating climbs to 6,000 pounds thanks to a heavily-revised independent front suspension. The truck's steering has been enhanced (a new, larger steering gear, power steering pumps and linkages) in order to better handle the increased front axle weight rating and reduce overall steering effort.

GMC says this upgraded front suspension is smoother riding and more easily adaptable to handle specific workloads than the competition. Backing it up is a new asymmetrical leaf-spring rear suspension with wider leafs, resulting in a higher payload capacity and less axle-hop. New shocks and hydraulic body mounts smooth everything out. What's more, any 4WD model can now be fitted with a snow plow. Slowing it all down are 14-inch brakes standard on all four corners to match the truck's increased weight and tow ratings.

All these impressive increases in capability come thanks to 11 all-new, fully-boxed frames to underpin the 11 cab and box configurations. GMC says the new frames are five times stiffer on their own while the hydroformed front sections are 125% stiffer. GMC even did the aftermarket a favor and added access holes in the frame for a gooseneck trailer hitch.

In the end, we're left with some important questions. Will GMC and Chevy best Ford in the power wars? Will the Sierra Denali HD be more comfortable and luxurious than the Ford Super Duty King Ranch? Does the Ram Heavy Duty stand a chance? We'll just have to get all the trucks together and find out. Stay tuned.

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