2011 GMC Sierra and Chevrolet Silverado Heavy-Duty technical deep dive *UPDATED*

Poltergeist

Ghost in the Machine
Aug 1, 2006
29,563
1
36
Ontario, Calif.
www.poltergeist.us
At first glance, the 2011 Chevrolet Silverado and GMC Sierra heavy-duty pickup trucks don't appear to have changed much compared to their 2010 counterparts. But don't let their familiar faces fool you, because virtually all of the greasy bits have been substantially upgraded or replaced entirely. Like the competitive heavy-duty trucks from Ford and Dodge, General Motors offers its trucks in a huge array of configurations with varying passenger, payload and towing capacities and an array of gasoline and diesel engines.

We drove seven different variants over two days in the Allegheny mountains of western Maryland along with the latest models from Dodge and Ford for comparison's sake. While the sales volume in the heavy-duty truck segment is smaller than it was at its peak a few years ago, it is still hugely profitable and comprises about 25 to 30 percent of all pickup sales.

As GM lurched toward bankruptcy last year, it culled its Saturn, Hummer and Pontiac brands, and sold Saab. Along with Buick, many armchair quarterbacks of the industry wondered aloud why GMC was preserved since its lineup consists of nothing more than badge-engineered Chevy trucks – it was thought that GMC could be shut down and Chevrolet could pick up the slack. However, when company executives sat down with the Obama administration's auto industry task force to review the business plan, one look at GMC's numbers ensured its survival.

Contrary to what logic might presume, GMC and Chevrolet truck buyers aren't really one and the same. GMC buyers are generally younger, better educated and more affluent. Perhaps best of all, those opting for Sierras are more likely to pick higher trim levels, crew cabs, diesels and add accessories – all of which do wonderful things for profit margins. Unlike Ford's Mercury division, which saw its sales shrivel in the past decade, GMC is thriving and the future could be even brighter as new models follow the path of the Acadia and Terrain with more unique styling. For now, however, except for the Sierra Denali, GMC and Chevy pickups are essentially the same. Thankfully, that's no bad thing as you'll soon see.

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The Silverado and Sierra HD pickups are available in so-called 3/4-ton 2500 models and one-ton 3500 models. As you might guess after a quick perusal of the spec sheet, the 3/4- and one-ton designations are little more than a carryover nomenclature from bygone days when they were limited to those payloads. As all trucks have become more capable, even the light-duty 1500 can carry over 1,500 pounds. Depending on the configuration, 3/4-ton 2500 models now accommodate up to 4,192 pounds and the one-ton 3500 can haul 6,635 pounds. Not coincidentally, both of those figures are ever so slightly better than Ford's corresponding F-250 and F-350 Super Duty models.

While Dodge has applied the styling of the latest light-duty Ram to its new HD trucks and Ford has fitted its F-Series with the boldest looking grille we've seen yet, GM has taken a more conservative approach. The front bumpers on both trucks are slightly reshaped, with bigger air intakes below the grille and the Sierra gets a perforated three-bar look similar to the Terrain CUV. Other than that, the sheetmetal carries over. As before, these HD pickups are available in regular, extended and crew-cab styles with 6.5- or eight-foot cargo boxes. Both the 2500 and 3500 are available with the single-wheel rear axle while the 3500 can also be outfitted with the dual-wheel rear axle. Most of these combinations are also available with either a 6.0-liter Vortec gasoline V8 (below, left) or the 6.6-liter Duramax diesel V8 (below, right) and rear– or four-wheel drive.

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Cab choices have also been carried over from the 2010 models with two different configurations available. Lower-end work truck models have a decidedly cheap looking instrument panel with hard plastics in a couple of different shades of gray. The matte finish may be dull and uninteresting, but this is a work truck first and foremost, and the space and ergonomics don't offer anything to complain about. Audio and climate controls on the center panel are pushed up between the vents, leaving a clear area under the dash for the legs of a center passenger. The most basic variants come with manual crank windows and a 60/40 split front bench seat that allows the driver some independent adjustability.

High-end models with the two-seat first row layout feature a full-length center console and the same dashboard that we're used to in GM's Tahoe and Yukon SUVs. The console offers plenty of storage space for log books, phones, cameras and whatever else a crew boss might need to stow – including a laptop computer. General Motors has no current plans to offer an equivalent to Ford's "Work Solutions" package, arguing that while the functionality it offers is indeed very useful, it's also very expensive.

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Instead, like many other GM vehicles, the HD trucks now offered with Autonet WiFi. Autonet provides a small wireless router with a built-in 3G mobile broadband modem. As soon as the truck is started, the router fires up, connects automatically and provides internet access to anyone within about 50 feet of the vehicle. With Autonet and OnStar's built-in GPS receiver, commercial truck users can use their existing laptops or netbooks to do much of what is already possible with Work Solutions. The biggest missing function is the tool tracking capability, but Vehicle Line Executive Rick Spina told us that when GM spoke to truck owners, they were told that the number of tools lost or left behind on-site typically adds up to far less than the cost of Tool-Link.

Peel away the bodywork and almost everything else is new, starting with the frame that forms the foundation of these beasts. The two main longitudinal rails are still hydro-formed, but they are now fully boxed from bumper to bumper. Only the larger chassis cabs retain a C-channel rear section to facilitate mounting whatever they end up carrying. A stiff frame is critical to durability and improving ride and handling, and in the not so distant past it was common to see the bed and cab of a pickup truck quivering independently over rough pavement. This new chassis and re-worked suspension, however, has greatly reduced that tendency and contributes to improved payload and towing capability.

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At the front corners, an independent control-arm suspension setup is retained, and it's a unique setup in this segment. The control arms are now wider than before to foster better control and isolation. At the rear axle, the leaf springs have gone from 2.5 to three inches in width. According to GM engineers, the wider springs reduce the internal stresses, thereby improving durability and load carrying capacity. The leaf-spring-axle configuration is now asymmetrical for the first time, a move that cuts down on axle windup under acceleration and braking, neatly improving handling at the same time.

Hanging off the ends of the suspension members are bigger brakes than have ever been fitted to a GM truck. The rotors have grown from 12.8 to 14 inches in diameter at both axles and the swept area of the pads has increased by 13 percent. As recently as the late 1990s, applying the brakes in a fully laden GM truck could be a nerve-racking experience. Back then, pedal feel was similar to stomping on a wet sponge, and your work boot might move through one-third to one-half of the pedal travel before any significant amount of retardation occurred. The new calipers and their resultant brake feel are much stiffer than before, eliminating much of that marshmallowy feel. The net-net is confidence inspiring stopping power, especially when the truck is loaded.

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For 2011, all single-rear wheel 2500 and 3500 models also receive full electronic stability control with trailer sway control. The system detects if the trailer is starting to oscillate back and forth as it would before washing away completely. If the sensors detect eminent calamity, the system alternately applies the truck's brakes from side-to-side until everything settles down again.

The 364-horsepower 6.0-liter Vortec V8 and 6L90 six-speed automatic are carryover from 2010, but they remain among the best gasoline truck engines available. However, for those who really need serious hauling capability, the optional 6.6-liter Duramax diesel V8 and Allison 1000 six-speed automatic transmission are the only way to go. Unlike the Blue Oval's Scorpion V8, the Duramax is not all-new, but it is heavily revised. Like other modern diesels, it now has a high-pressure common-rail injection system with piezoelectric injectors that can execute multiple pulses per ignition cycle. This allows the fuel delivery to be more precisely metered and spread out over a longer time so that combustion temperatures remain under control. Lower combustion temperatures help reduce NOx production so that the Duramax can meet the 2010 emissions standards.

The engine changes alone are not enough to make the Duramax clean. Like the Super Dutys and all of the six-cylinder German diesels in the States, GM has also incorporated a urea injection system to clean up whatever residual NOx is produced. The heated, 5.3-gallon urea tank is mounted on the frame rail adjacent to the oxidation catalyst and needs to be refilled about every 5,000 miles along with oil changes. In addition to running more cleanly, the Duramax also has improved fuel economy by about 11 percent, more power and torque and is much quieter than ever before. Heavy-duty trucks don't have to carry EPA window stickers, but according to GM's Spina, the 3500 diesel achieves a combined rating of about 17 miles per gallon.

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All recent heavy-duty trucks have had a tow-haul mode that allows the driver to lightly apply the brake pedal for a couple of seconds and trigger automatic transmission downshifts when on a downhill grade. The diesel trucks also add exhaust gas braking that typically uses a bypass valve to increase the exhaust back pressure in the engine, forcing it to slow down. When carrying a heavy load or towing, this can help reduce the workload on the brakes dramatically. For its 2011 trucks, GM has taken this technology a significant step further. The existing exhaust gas braking systems are basically just on-off controllers, but with the new Duramax, the system monitors vehicle speed when you set the cruise control, and in addition to maintaining speed when going uphill, it uses the variable geometry vanes in the turbocharger to adjust the backpressure just enough to hold a constant speed when going downhill. Even without using the cruise control, just tapping the brake pedal for a few seconds will trigger exhaust braking and hold the speed on a grade without using the binders.

All of which is a long way of saying there's a lot of fancy technology at work underneath what most people think of as just simplistic beasts of burden. As it's not uncommon for the people who drive these trucks to accumulate 100,000 hard miles each year, it's particularly important to understand how well the drive.
 

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Poltergeist

Ghost in the Machine
Aug 1, 2006
29,563
1
36
Ontario, Calif.
www.poltergeist.us
Usually whenever we head out to a new vehicle press launch, we have to sit through exhaustive technical and marketing presentations before we get a chance to climb behind the wheel. However, General Motors put us straight into a dual-rear wheel GMC Sierra 3500 crew-cab diesel upon our arrival in Baltimore. On the docket? A 130-mile trek from Baltimore airport to Rocky Gap Lodge in the Allegheny mountains of western Maryland with Vehicle Line Executive Rick Spina sitting shotgun.

We actually appreciated this 'backwards' approach, because it gave us the opportunity to develop some 'gut' impressions of these new trucks even before we got the attendant sales pitch. For a two-hour, mostly highway jaunt, the duallie SLT proved to be a surprisingly amiable companion, but it was just the first of seven different trucks we would drive over the next couple of days. Read on to find out what GM's new heavy duty trucks are like when sampled in a range of real-world conditions.

The SLT trim level on our first Sierra brought with it leather seats and steering wheel, navigation, power-adjustable pedals and just about everything else you can think of. The first thing we noticed is how quiet the Duramax diesel has become. The true degree of that silence wouldn't become fully apparent until the next day when we drove the Vortec-powered GMC Denali, but this certainly isn't the kind of bucket-of-bolts diesel we've become accustomed to when sitting next to them at traffic lights.

It wasn't just the engine that was quiet, everything about the cabin was very subdued. Of course, it's no Lexus LS, but especially considering how high up we were sitting on big truck tires, it was very impressive. Even with the barn-door sized towing mirrors, wind noise was kept to a minimum, and at highway speeds, conversations without raised voices were never a problem. Beyond the quiet, the crew cab was exactly that – with second-row seat room big enough to accommodate three adults in comfort. And for those times when extra protected storage was required, the rear seat cushions flipped up to provide a flat load floor.

The single most impressive aspect of the Sierra 3500 on that first drive was its ride quality. This one-ton truck had no load in the back, which in the past would have meant bouncing around on every expansion joint and bump. The roads in Maryland are certainly smoother than what we have to deal with back in Michigan, but the GMC was nonetheless a serene operator. With a curb weight of 7,387 pounds, the Sierra was also surprisingly quick, thanks to its 397 horsepower and 765 pound-feet of diesel torque. Past criticisms we've leveled at GM HD pickups with Allison transmissions included rough shifts and noisy gears, both of which have been addressed in this latest iteration. Seamless gear changes even under hard acceleration are now part of the HD's MO.

The next day, the skies opened up as we started off in a Vortec-powered single-rear-wheel crew-cab Denali heading further west into the Allegheny mountains where we we would dip into West Virginia. Like other Denali models, the HD gets the usual perforated chrome grille, chrome bumpers and door handles and brushed aluminum interior trim for a little added flash. The Vortec was decidedly louder than the diesel, although actually in a very good way. The small-block V8 engine has the roar that we've come to know and love since time immemorial. Considering how quiet the rest of the truck is, the engine sound actually seems almost of out place, but we're not going to complain.

Like the duallie we drove the day before, the Denali was unloaded, and as we got further up into the mountains, the road surface quality worsened considerably even as it became more serpentine. Nonetheless, the GMC handled anything we threw at it with genuine pluck. We managed to trigger the ABS and stability control on wet pavement several times, and unlike past experiences with, say, the Toyota Tundra, the Sierra just tracked right where we pointed it. Even when we hit some mid-corner rough stuff, the rear end never once stepped out on us. Who would have thought a big truck could handle so well?

In addition to a bouncy ride and spongy brakes, the bad old days of heavy duty pickup dynamics had us expecting sloppy, overboosted steering. Thankfully, the days of being able to wiggle the steering wheel 5-10 degrees off-center with no real response are over at GM and Ford. The Generals have a new larger recirculating ball steering gear, which, in tandem with the improved contact patch control of the revised front suspension, results in steering response that's better than some cars we've driven. The GM trucks offered no disconcerting slack zones in the steering and actually provided pretty decent feedback as the cornering forces built while driving through the mountains. Our only complaint was that the effort felt a bit light at low speeds, but it firmed up nicely at higher velocities.

At our first vehicle swap point, we grabbed a Sierra 2500 crew cab, with a 35-foot-long, 9,000 pound (empty) travel trailer hanging off the hitch. After a quick primer from engineer Brent Deep on how to maneuver nearly 60 feet and over 16,000 pounds of truck and trailer, we headed out. Our tow truck was again powered by the diesel, and even with all that mass to drag around, the engine never felt strained, even though our drive route contained several extended grades of seven to eight percent. After getting used to checking the spotter mirrors to make sure we didn't clip any curbs or cross center lines, we set the cruise control at the 55-mile-per-hour limit and let the truck go to see how well the new smart exhaust brake worked. In short, it was brilliant.

As the truck crested a hill and headed down, the speed would creep up by about 2 mph, which triggered the transmission to downshift and the turbo control to kick in. From there, our velocity was held in check with our set speed all the way down the hill without any intervention on our part. The first couple of times we used the system, we hovered our foot over the brake pedal just in case, but once we were confident the system worked, we just put our foot down and let the truck do the work. The beauty of this system is that it works entirely without applying the brakes. Now, if GM would just add radar-based adaptive cruise control and integrate the turbo and transmission control to provide primary deceleration in addition to braking, this system would be near perfect. You could follow traffic, maintaining a safe distance without using the brakes most of the time.

Even when you do have to use the brakes, the newly solid pedal feel makes modulation a breeze. The most important benefit of all this is the confidence it inspires while driving with either a payload or a trailer. Towing in hilly terrain is now possible with much less concern about using up all of the brakes prematurely, leaving drivers to focus more on where the truck and trailer are on the road.

After lunch, we switched to a crew cab Chevy Silverado 2500 with 3,000 pounds of ballast in the bed. Frankly, the big Duramax barely noticed the 1.5 tons worth of steel, seemingly accelerating just as effortlessly as the unloaded trucks did. Going around corners, the extra mass manifested itself as added inertia resisting directional changes, but it did help to dampen vertical motions even more than the unloaded truck. Another factor contributing to the comfortable ride, even in the work-truck variants like this one, is the use of two hydraulic body mounts at the rear of the cab. The front end is tied down with traditional rubber mounts, but the hydraulic units out back give the engineers more latitude to tune motions in several directions and focus on specific frequencies that are annoying to passengers.

After our return to Rocky Gap, the trucks were available with their Ford and Ram rivals for back-to-back comparisons over a shorter loop. Only one Ram 3500 was available, and it was unloaded. Our gut reaction? If you prefer old-fashioned, sloppy truck steering, this is your ride, as it has plenty of free play just off-center and it's overboosted effort everywhere.

Of the two Super Duty F-350s, one was loaded with 3,000 pounds of ballast and the other was towing a trailer identical to the one hooked to the GM truck we sampled earlier. The first thing we immediately noticed was that the new 6.7-liter Scorpion diesel is simply not as refined as the Duramax. It produces plenty of power and torque, but at light accelerator applications, it still exhibits some of the traditional clatter traditionally associated with diesels. Put your foot into it at more than about 35-40 percent throttle (yes, we know a diesel has no throttle) and it settles down nicely into a similar growl to the Duramax. Since this is an all-new engine, perhaps the Blue Oval's engineers are still coming to grips with tuning it.

The other big difference we noticed with the Ford was in the area of ride comfort, which is clearly inferior to the Sierrado twins. Parts of the drive loop included some small, medium frequency waves that were noticeable but not intrusive in the Sierra. The Ford, on the other hand, felt jiggly over these same surfaces, even with 3,000 pounds of ballast in the bed. The Ford's steering was just as slop-free as the GM trucks, but on the demerit side, it felt distinctly overboosted.

We took out the Sierra and F-350 with identical trailers for some side-by-side testing on the short loop. While the Ford has exhaust-gas braking, it is of the traditional on-off variety rather than the variable control setup used by GM. Ford confirmed to us that there is no turbocharger control currently implemented in its tow-haul mode. The result is that while the system slows the vehicle on downhill grades, speeds can creep up unless you apply the brakes.

When accelerating, the Scorpion doesn't feel as brawny as the Duramax, even though the GM diesel only has a 7-horsepower and 30 pound-feet of torque advantage. Seizing the opportunity, we grabbed some of our colleagues and lined up the Sierra and F-350 (both with 9,000-pound trailers) for an informal drag race. The Ford did get an initial jump on the GMC, but then the Sierra quickly caught up and pulled away. Some seemed to think that Ford might be doing some torque limiting with its engine, perhaps to protect the transmission. Whatever the case, the GMC offered better performance both uphill and down.

For our final drive stint, we returned to a single-rear-wheel Sierra 3500 crew-cab with a 3,000-pound payload for the return run to Baltimore's airport. This time, we reset the fuel economy readout in the trip computer, and in deference to the large population of eagle-eyed Maryland state troopers, we set the cruise control to the state mandated limit of 65 mph. Over the next 133 miles through the Allegheny mountains and then into the flatter area near the city, we rarely touched the accelerator or brake except when stuck behind a semi. The cruise control maintained a steady speed over hill and dale and we made no attempt to optimize our mileage. As we rolled into our destination, the readout in the instrument cluster read a very impressive 19.8-mpg average for the diesel V8 – not bad for nearly 11,000 pounds of truck.

As you might expect, these GM heavy-duty trucks are not inexpensive, with pricing starting at about $28,000 and easily running over $60,000 when loaded up with all the toys. Of course, we've been in some gussied-up half-ton pickups whose Monroneys breech 50k, and given all that these HDs are capable of, we don't find the bottom line off-putting. Besides, people generally buy HD trucks because they need them – very few are purchased as lifestyle vehicles. As Chevy truck marketing manager Tony Truelove tells it, this is the "most expensive tool" in an operator's kit.

In terms of raw capabilities, these new GM trucks edge the Fords in most categories, but not by any amount big enough to be truly meaningful. For example a towing capacity of 21,700 pounds vs 21,600 for the Ford is not likely to sway a buyer one way or the other. What may tilt the scales toward GM, however, is its superior ride quality, engine refinement and features like smart exhaust braking. We suspect anyone who needs this kind of truck is unlikely to be disappointed by either of these leaders, but they might find themselves feeling a bit more refreshed after an extended stint in a Sierra or Silverado HD. In the gritty world of long distance heavy hauling, that's perhaps a luxury worth more than any other.
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
0
Wyoming
Contrary to what logic might presume, GMC and Chevrolet truck buyers aren't really one and the same. GMC buyers are generally younger, better educated and more affluent. Perhaps best of all, those opting for Sierras are more likely to pick higher trim levels, crew cabs, diesels and add accessories – all of which do wonderful things for profit margins.

hahaha In todays day and age of everyone whining and complaining about being politically correct, stepping on toes etc.. Im actually kind of surprised they threw this statistic out there like that.

obviously I have a chevy and it doesnt bother me (and im sure it wont bother any other chevy guy on the forums here), but I could see some chevy guys out there taking it literally/as an insult and maybe getting their feathers ruffled.
 
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DAVe3283

Heavy & Slow
Sep 3, 2009
3,727
296
83
Boise, ID, USA
Contrary to what logic might presume, GMC and Chevrolet truck buyers aren't really one and the same. GMC buyers are generally younger, better educated and more affluent. Perhaps best of all, those opting for Sierras are more likely to pick higher trim levels, crew cabs, diesels and add accessories – all of which do wonderful things for profit margins.
hahaha In todays day and age of everyone whining and complaining about being politically correct, stepping on toes etc.. Im actually kind of surprised they threw this statistic out there like that.

obviously I have a chevy and it doesnt bother me (and im sure it wont bother any other chevy guy on the forums here), but I could see some chevy guys out there taking it literally/as an insult and maybe getting their feathers ruffled.
I'm kind of surprised to see that as well. The GMC guys may be better educated and more affluent, but they've got no common sense. Common sense tells you that you can get the same truck labeled "Chevy" for less money, then throw the difference into upgrades! Oh yeah! That, or buy a used truck, and have lots of cash left over to... pay college debts with. Sigh.
I drive a Chevy and would never buy a GMC.
I'd buy whatever was cheaper, which is most likely going to be a Chevy. I can't stand throwing money away, even if the GMC trucks do look a bit better (IMO). Although I liked the '03-07 Chevys better than the GMCs.
 

Diesel Pilot

Hat? Suitcase? 50 BMG?
Aug 9, 2006
1,424
0
36
47
Pickerington, OH
I think it's hilarious that the article basically said that the new trucks beat up on the other 2 (Dodge and Ford) pretty good. But, we already knew that so we are picking on each other because that's the only real competition.:rofl:

I've got love for the Chevy trucks too. Too me, and just my opinion, the GMC has edged the Chevy in the looks department since '02. Now on the other hand, I think the Tahoe/Suburban is miles ahead of the Yukon in looks.

Also, isn't everything bigger than a 5500 a GMC now? I couldn't find any info on current medium duty Chevy's. I might be wrong though.