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 |  Mar 10 2010, 10:56 AM

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A month after the debut of the all-new 2011 Chevy Silverado HD, GMC has now announced its version of the work truck, the Sierra Denali HD. Powered by the same 6.6-liter Duamax engine and 6-speed Allison transmission, the truck gets best-in-class power of 397-hp at 3000 rpm and best-in-class torque of 765 ft-lbs at 1600 rpm. This tops the new Ford F-Series, but only slightly, while coming slightly under the new Ford truck in both payload and tow ratings, with a 6,335 lb. and 20,000 lb rating, respectively. The trucks conventional (non-fifth-wheel) towing cappability is up significantly, to the tune of 23 percent, and is now rated at 16,000 lbs.

The engine block itself is a carry-over from the past model but the majority of moving engine parts are new, as is the entire fuel system. NOx emissions are also down 63 percent thanks in part to an exhaust after treatment system that is used because it won’t interfere with the engine’s ability to create power. The Diesel Exhaust Fluid (DEF) used in the process does require refilling every 5,000 miles. In addition, the new engine is B20 biodiesel capable.

As for the new Allison transmission it has been strengthened to work with the added torque of the new engine and features an optional exhaust brake, Power Take Off and a Driver Shift Control (DSC). It’s also designed to work with the new Duramax engine to give improved fuel economy by 11 percent and GMC says to expect a fuel range of 680 miles on the new 36 gallon tank.

In addition to the fuel economy improvements, GMC claims improved acceleration with Duramax/Allison combo, resulting in a 0.3-second improvement to 60 mph and a 0.5-second improvement in the quarter-mile for a rating of less than 9 and less than 16 seconds respectively.

Like it’s Chevy counterpart, the Sierra gets a new front suspension with forged steel upper control arms and cast iron lower control arms with the new front independent suspension now delivering a 25 percent improved front axle weight rating. The new 6,000 lb rating now means a snow plow can be used on all 4WD cab models equipped with the snow plow prep package. In addition, rather than a single torsion bar like on the previous model, the 2011 gets five different torsion bar rates for five different gross axle weight ratings, allowing height adjustability in accordance with the weight of a snow plow or other accessory.

As for the rear suspension, the leaf springs are now 20 percent wider, helping to improve the truck’s rear gross axle weight rating. Now 2500 models are rated to 6,200 lbs, while 3500 models get a 7,050 rating for single wheel or 9,375 of dualies. The new rear suspension is also designed to reduce wheel hop.

We could probably go on forever discussing the upgrades to the new 2011 Sierra HD, so we’ll try and wrap this up with a few more important things you should know. For 2011 the brakes are larger, measuring 14-inches at all four corners while the swept area of the brake pads has been increased with 13 percent more area covered on the front rotors and 17 percent more covered on the rear. Gone are 16-inch wheel fitments, with 17s now the new base wheel, while 20s can be had on the 2500HD.  Safety equipment includes StabiliTrak and Trailer Sway Control on all single-rear-wheel models as well as a new Hill Start Assist feature, that holds the truck for 1.5 seconds when leaving a stop on a hill. GMC also says that under heavy load it has reduced noise vibration and harshness (NVH) by as much as 30 percent.

Finally, let’s not forget the standard engine, a 6.0-liter Vortec V8 and six-speed 6L90 automatic transmission., It gets 360-hp at 5400 rpm and 380 ft-lbs of torque at 4200 rpm. A total of 90 percent of the engines torque is available from 2000 rpm allowing for a 13 percent increase in fifth-wheel towing for a total tow rating of 14,700 lbs.

GALLERY: 2011 GMC Sierra Denali HD

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Get all the 2011 GMC Sierra Denali HD details and model info after the jump:

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