2011 GMC Sierra and Chevy Silverado HD Trucks First Drive - Web ExclusivePosted in How To on June 15, 2010 Comment (0)
Let's establish something here and now before we proceed further. This test-drive and evaluation was conducted on this vehicle in terms of its capabilities as a tow rig, not a Rubicon-ready rock crawler. Frankly, there's only one option in the 3/4 to 1-ton class for a serious off-road truck. I think we all know what model that is. Hint: Its name ends with "Wagon." But if you're looking for a truck that will tow your toy hauler, travel trailer, dune buggy, purpose-built rock crawler or other non-street-legal vehicle across the miles, this review is for you.
At first glance, there's not a great deal distinguishing the 2011 GM Heavy Duty trucks from their 2010 counterparts. The lower-front grille openings on the diesel models are slightly larger. And the hoods feature a new design. But aside from some subtle styling tweaks, the trucks look essentially identical to last years' models. But under the skin, these trucks are about as all-new as trucks can be. Whereas last years’ models had C-section frame rails, the new models' frames are fully-boxed, stem to stern. For you live axle purists, you'll be disappointed to learn that GM's long-standing commitment to torsion bar front suspension remains for 2011. Although the basic design is carryover, the new front suspension system offers up to a 25-percent greater front axle weight rating of up to 6,000 pounds front gross axle weight, allowing a snow plow to be used on all 4WD cab configurations with the available snow plow prep package.
The 2011 HD models' front suspension now features new forged steel upper control arms that are stronger and lighter than their predecessors. The new lower control arms are made of precision-machined cast iron to handle the greater loads. Unlike the 2010 models where only one torsion bar rate was used across all HD models, the 2011 models feature five different torsion bar rates for the various models' configurations. This helps stabilize the range of trim heights of various models under load, while enhancing appearance, handling, durability, tire wear and alignment. The trim height is adjusted on each bar via a single bolt, allowing the height to be changed to account for the weight of a snow plow or other accessories. The HD front suspension now uses a pair of urethane jounce bumpers on each side, instead of one, for improved load management; and there’s a new upper shock mount attachment design that's positively connected to the frame with two fasteners. This design eliminates squeaks and clunks, while supporting higher load capability and increased durability.
In the rear, a new larger asymmetrical leaf-spring design contributes to improved ride and handling characteristics. The asymmetrical design is derived from unequal front and rear spring half lengths, which minimize axle hop and enhance traction control efficiency.
The 2500HD models feature a two-stage leaf-spring design, while 3500HD models have a three-stage design. All models feature 3-inch-wide leaf springs that are 20-percent wider than previous models. The larger leaf-spring design supports increased rear gross axle weight ratings across the board. On the 2500HD models, the rating is 6,200 pounds – up from 6,084. On 3500HD models, the rating increases to 7,050 pounds on single-rear-wheel models and 9,375 pounds on dual-rear-wheel models – the latter representing a nearly 14-percent increase over the previous 8,200-pound rating.
Indeed, in driving the various models, both laden and unladen, the ride was remarkably comfortable and compliant for a heavy-duty truck. Even the bare-bones, vinyl seats, crank windows dump truck version we drove was remarkably smooth-riding, with very little road noise.
Making the Grade
GM is particularly proud of the new integrated "smart" exhaust brake on the 2011 Duramax models. Actuated by a button on the dashboard, the system utilizes the turbine control of the variable geometry turbocharger and the compression of the engine to generate backpressure, slowing the vehicle without having to apply the brakes. It is integrated with the cruise control feature, and varies the braking to account for the grade and vehicle load. I can attest being a towing rookie, and being unceremoniously thrown at two of the biggest trailers used at the event (a camper/horse hauler, and a Bobcat on a trailer along with a substantial payload in the bed), that I never felt that I was going to lose control, even on the steepest grades. Just a few gentle taps of the brake pedal put the system into action, downshifting smoothly and methodically to maintain a safe vehicle speed.
But it's one thing to be able to go down the hill, but what about climbing it? Again, GM's new HDs don't disappoint. Although the Cummins enjoys a cult-like following in the HD truck realm, GM is not cowering in the corner whimpering for mommy when it comes to diesel power ratings. Quite the contrary, in fact. The new 6.6 liter LML Duramax cranks out an almost Class-8 level 397 horsepower and an eye-popping 765 lb./ft. of torque...from the factory. To put it in perspective, that's 47 horsepower and 115 lb./ft. more torque than the current 6.7 liter Cummins offered in the Dodge, and 7 horsepower and 30 lb./ft. more than even Ford's all-new 6.7 liter "Scorpion" turbodiesel. The Duramax's NVH levels are not quite as remarkable as they were 10 years ago when the engine was initially introduced among admittedly agricultural competitors at the time, but the LML’s familiar muted gravelly cadence is far from objectionable, whether at idle, cruising or wide-open throttle.
Even towing the gargantuan horse trailer and weighty Bobcat and payload, the combination of the Duramax and Allison transmission got the vehicle and load up to speed without incident or drama, able to merge comfortably with the flow of traffic, and maintain speed going up grades. Nearly all of the trucks at the event had either a trailer attached or a substantial payload in the bed. Considering the workhorse nature of this vehicle class, it wasn't unexpected, and probably an effective demonstration of the vehicles' capabilities. However, it was beginning to look like I wasn't going to get a chance to experience the full power of the new Duramax unladen. Fortunately, toward the end of the event, I was able to snag an unladen 2WD 3500 dually. Even in one of the largest, heaviest configurations offered (more than 7,500 pounds), the new Duramax moves the big truck along with relaxed confidence, easily and swiftly reaching more than 80 miles per hour without breaking a sweat.
It's a Gas
Although the Duramax admittedly had the more mouth-watering specifications, for comparison's sake, as well as doing my journalistic duty, I drove a model equipped with the 6.0 liter Vortec gas V8. The diesel is the obvious choice if you're regularly doing heavy hauling and towing, but the gas model remains the overwhelming favorite with utility and service fleets, likely due to its substantially lower initial purchase price than the Duramax (about $8,000 less). With a torque rating literally half that of the diesel, I wasn't expecting much excitement when getting behind the wheel of the gas version. But I was pleasantly surprised.
Sharing its basic architecture with the Camaro and Corvette's LS3 V8, and its bore and stroke dimensions with the previous LS2 Corvette, the 360-horsepower L96 6.0 has a surprisingly aggressive, muscle car-like exhaust note under-the-whip. And like the LS2 and LS3, it has a lively, free-revving personality. Although that may seem like an odd match for a heavy-duty truck, it gave the gasser an entirely unique character compared to the Duramax's gruff, relaxed demeanor. The downside to having substantially less torque than the diesel was much busier shifting in the gas version, downshifting much more frequently than the diesel to get into its higher-revving powerband. But if your truck use is mostly light-duty payloads and occasional heavy towing, and don't rack up a lot of miles year-by-year, the gas model is a rational choice.
Overall, the 2011 GM Heavy Duty trucks are a substantial improvement over their predecessors, as well as formidable competitors to Ford and Dodge. If you're looking for comfort and refinement in addition to no-nonsense heavy duty capability, the new GM HDs should be on your shopping list.