The following review is for a 2013 Model Year. There may be minor changes to current model you are looking at.

Professional capability, Cadillac comfort.

Introduction

GMC Sierra HD heavy-duty pickups are well suited to real-world use and abuse. They can haul tons of brick and cement and tow the concrete pump, then turn around to be used for a night on the town or grocery shopping while the fifth-wheel's left in camp or the horses are in the corral. If your hauling happens once or twice a year or you tow a bass boat or ski boat, then the 1500-series may be better suited. If your load is heavy, however, or you do a lot of towing, the Sierra HD is the ticket, especially with the powerful diesel engine. We found it towed a 5000-pound trailer load like it wasn't there and a 15,000-pound trailer with ease. 

A luxurious Sierra HD Denali model is available in both 2500 single-rear-wheel and 3500 dual-rear-wheel models. The 2013 Sierra HD Denali comes standard with heated and cooled front seats, leather-wrapped heated steering wheel and rear camera. Polished aluminum 17-inch wheels are standard on Sierra HD Denali duallies and are available on Sierra HD SLT duallies. Denali is GM's answer to Ford's King Ranch and Ram's Lariat Longhorn. The availability of the Sierra HD Denali gives the GMC buyer more a more luxurious option than is available to the Chevrolet buyer. 

The GMC Sierra HD is built on the same chassis as the Chevrolet Silverado HD and shares all the sheetmetal, including the hood, with it. Different hood trim, lights, grille, wheels and ruby red badges distinguish the GMC from the Chevrolet. 

Changes for 2013 are minor. Among them: The 2013 Sierra HD offers a bi-fuel CNG 6-liter gas engine on 2500 Extended Cab, and the 397-hp diesel is available on 3500 Chassis Cabs and pickup box-delete Silverado HDs. The GMC Sierra HD line of heavy-duty pickups was reengineered for 2011, with a new frame, new front and rear suspensions, bigger brakes, more powerful Duramax 6.6-liter turbo diesel and a luxurious new top-line Denali. 

As with all heavy-duty pickup lines, the Sierra HD offers plenty of configurations with three cab styles, two bed sizes, single or dual-rear wheels and 2WD or 4WD. A 6.0-liter gasoline V8 is standard, rated at 360 horsepower in 2500 models and 322 hp in everything else. It isn't quite as powerful as the competition's gas engines. 

The 6.6-liter turbodiesel with 765 pound-feet of torque (more than twice the gas engine's) is competitive with Ford's Super Duty at 400 hp and 800 lb-ft and Ram's 350 hp and 660-850 lb-ft. GM and Ford use 6-speed automatics in their trucks; Ram offers a choice of six-speeds, manual or automatic. 

Sierra HD offers two distinct interior concepts, one bred for work, function and simplicity, the other emphasizing luxury and features over outright seating space. Almost anything you can get in a GMC sport-utility is available here, including OnStar, a subwoofer-equipped sound system, rear-seat entertainment, driver memory system, heated leather seats and a moonroof. For the entry price of around $29,000 you get a functional pickup with real load-carrying ability, but for big towing in a properly equipped diesel expect to pay much more. Options can add up quickly, the diesel engine ($7195) and its required transmission upgrade ($1200) among the most expensive. 

The trick in buying the right GMC Sierra HD is to give fair consideration and choose wisely. Compute the permutations among three cabs, two weight classes, two beds, two engine/transmission combinations, two drive systems and four trim levels, and then sort out options that cover everything from a diesel radiator cover to rear park assist, and you can see why prices run from that base $29,000 to well past double it. 

Lineup

The 2013 GMC Sierra HD offers three cabs, two beds, five wheelbases and four trim levels. The Vortec 6.0-liter V8 and 6-speed automatic comes standard, the Duramax diesel with a stronger Allison 6-speed automatic is optional ($8,395). 

From the least expensive version, plan on adding $2,000-$3,000 to step up from regular cab to Extended cab, or from there to Crew Cab. Figure $200 more for a long bed version. Add about $3,000 for four-wheel drive. 

Sierra WT models are work trucks with gray vinyl upholstery, rubberized floor covering, black door handles and mirrors, steel wheels and floor-shift for 4WD. They come with air conditioning, AM/FM stereo, cruise control, driver information center, 40/20/40 manual-recline front seats, rear bench seat, tilt wheel, chrome grille and bumpers, tow hooks, intermittent wipers, and dual dash power outlets. The WT Crew Cab has a 60/40-split rear bench seat. Options on WT include stereo upgrades, OnStar, 18-inch wheels, camper mirrors, locking differential, trailering equipment, power windows, mirrors and locks, integrated trailer brake controller, deep-tint glass and bucket seats. 

Sierra SLE versions improve with cloth upholstery, carpeting (though the WT floor is available), 40/20/40 front seat with locking console storage, split-fold rear seat, AM/FM/XM/CD/MP3 RDS stereo, OnStar with six months' service, cruise control, aluminum wheels, power heated mirrors/windows/door locks, visor vanity mirror/lights, side moldings and electric-shift for 4WD. SLE options include dual-zone climate control, navigation and backup camera, backup camera in mirror, power passenger seat for the 3500 Crew Cab, steering wheel controls, power sliding rear window, power heated camper mirrors, 20-inch wheels for the 2500, locking differential, Z71 off-road package with shocks, bump stops, 36-mm front antiroll bar, and skid plates. 

Sierra SLT upgrades with leather, 10-way power heated front seats and two-person driver memory, dual-zone climate control, Bose DVD audio system, Bluetooth, console, auto-dimming mirrors (3), steering wheel controls, fog lamps, paint-matched trim, power folding mirrors w/signals, 18-inch polished forged aluminum wheels, locking differential, trailer equipment and integrated trailer brake controller. SLT-level upgrades include navigation and rearview camera, rear-seat entertainment, moonroof, power sliding rear window, power heated camper mirrors, and 20-inch wheels on 2500. 

Denali models come in 2500 or 3500, single or dual rear-wheel configurations, 2WD or 4WD, short bed or long bed. Denali is Crew Cab only. Denali gets a unique four-bar grille, body-color bumpers, chrome door handles, chrome accents, polished forged aluminum wheels, and EZ-Lift locking tailgate. Inside, Denali adds heated steering wheel, heated and cooled front seats, moonroof, unique brushed aluminum trim, power-adjustable pedals, a Bose premium surround audio system with 6CD/USB, Bluetooth, and 12-way power seats. Options include rear-seat entertainment. Denali comes only in black, gray, or white. 

Optional on most trim levels are roof marker lamps ($55), skid plates ($150), snow-plow prep for 4WD, fast-idle switch ($200), camper/fifth-wheel wiring ($35), myriad dealer options and for diesels, dual 125-amp alternators ($270) and radiator covers ($55) for cold states. 

Safety equipment includes frontal airbags, front seat belt pretensioners, and StabiliTrak on single-rear wheel models. Optional equipment includes front-side airbags and front side-curtain airbags, OnStar, backup cameras and integrated trailer brake controller. 

Walkaround

GMC Sierra HD shares its mechanical bits with the Chevrolet Silverado HD, but they are not visually identical. Different grilles, lights, trim, wheels and badges distinguish the two. Denali models use unique elements of those distinctive parts to separate themselves from other Sierra HDs. 

The wallpaper sized, ruby red GMC logo makes its origin obvious. The bumper that blends into the fenders gives the front an integrated look that lacks the big bumper-to-grille opening characteristic of vehicles with separate bodies and frames. The increased frame stiffness allows smaller gaps between panels and helps the Sierra HD ride quieter than Super Duty cabs. 

Extended cab models have rear doors that open to the rear after the front doors have been opened, with windows that roll down to minimize rear seat claustrophobia. Ford's Super Cab uses the same system, while Ram HD's mid-size cab has four conventionally opening doors. 

The box sides are deep. The tailgate has an optional lock and assist for closing it with less effort. The cargo management option fits rails to three sides of the bed, which can be used for tie-down points and to carry a variety of tool or utility boxes. The dual-element mirrors, some of which are heated and power-fold for drive-through lanes, aid rearward vision when towing. 

Most heavy-duty pickups have external dimensions close to each other and the Sierra is similar; more than six-and-a-half feet wide outside with room for a 4x8-foot sheet of building material to ride flat in the long bed. 4WD Sierra models are slightly lower than competing pickups, and that inch or two could make the difference in commercial garages or with critical fifth-wheel trailer/bed side clearances. 

Interior

The high-line Sierra SLT cabin feels just like the interior of a large luxury car, with a low-profile dash sporting lots of woodgrain trim, a compact instrument cluster with good gauges, three months of XM radio to get you hooked, and a center stack that rolls off the dash and right into a full-length center console. 

The Sierra HD SLT and Denali cabins are more car-like than truck-like: sleek, distinctly split between driver and passenger environments, and good fit and finish. Other Sierra models use a more conventional pure pickup layout, with a higher dash section that goes across the middle and leaves the center open for middle riders, manual-shift transfer case, or communications and safety equipment. 

Though not as stylish, the standard pure pickup dash is the more functional of the two and equally well assembled and up to date. It offers more options in small storage, a second glove box with an awkward latch, locking storage area with power point beneath the center seat section, more places to add accessory switches, radio and ventilation controls are up higher near line of sight, and the materials produce less glare in low-lying sun and night construction areas. Adjustable pedals and a tilt wheel are available, though the wheel does not telescope. 

The Regular Cab Sierra has room for an XL-sized gent and space behind his seat for coat and boots. Extended Cabs have a seat cushion that folds up for more storage and LATCH anchors for infant seats. Crew Cabs are the obvious choice for anyone hauling more than youngsters on a regular basis, just be sure the middle rider knows there is no headrest. 

Operating controls are clearly labeled and logically placed, and the shifter offers the typical D and 1 positions, with an M position and thumb tab for individually selecting any intermediate gear. 

If there's a drawback to the Sierra cabin it is the quantity of similarly shaped and labeled small buttons that butterfingers may have some issues with. Door switches won't let your dog power the window up, but he may still lock you out; fortunately, OnStar (and the turn-by-turn navigation it offers) is standard on most and includes a few months free service. As with a Mercedes, turning on the navigation system also switches on the radio, and you'll have to turn it all the way down if you don't want to hear it. 

The fact that the Sierra interior, especially on SLT models, is the most like a car will certainly find favor with those who need a pickup rather than just want one. Denali models may steal a few King Ranch or Laramie Longhorn sales. 

Driving Impression

Any differences in styling, interiors or engines aside, heavy-duty full-size pickup trucks are all about bragging rights numbers. At its redesign for 2011 the Sierra HD and Silverado HD had the highest ratings for towing capacity (both conventional hitch and fifth-wheel/gooseneck), payload capacity, and gross combined weight rating (GCWR, total truck, trailer, cargo, and passengers). 

Ford and Ram both caught up or surpassed at least some of those numbers, so for 2012 the GM HD pickups have raised the numbers again. Maximum ratings are: conventional trailer 18,000 pounds; fifth-wheel/gooseneck 23,100 pounds; payload 7222 pounds; GCWR 30,500 pounds. Conventional trailer and payload ratings slightly better the Ram, but the Ram rules towing with a top rating nearly 7000 pounds higher than the Sierra. 

Truck people talk frames and parts because they're the foundation. On the Sierra HD the foundation includes things like forged steel upper and cast iron lower front suspension arms like pieces used on older Land Rovers and the Mercedes Gelaendewagens rather than the aluminum and stamped steel of lightweight pickups. Everything was upgraded for 2011, right down to the bolts that hold the wheels on. 

Adding bigger parts is easy. What makes the GMC HD noteworthy is that the increase in capability comes with no sacrifice in ride quality, cab comfort, handling or control. GMC claims diesel highway fuel economy that suggests about 18.5 mpg, but honestly the only time you should be highway cruising in an empty HD is after you've delivered the cargo or trailer somewhere. No mention of city mileage, probably because the truck is 300-400 pounds heavier than its predecessor. We observed 10 mpg in the largest (dually) HD diesel pulling a four-ton trailer, for a short stretch. 

Later we drove a Denali 2500 4WD Crew Cab with the Duramax diesel engine for one week and 640 miles, including about 200 of those miles towing a 2500-pound racecar on a 3000-pound trailer, on both a winding mountainous freeway and in the city. Overall, we averaged 14.5 miles per gallon; a sleeker aero package and half the trailer weight than the dually cited above. The diesel's 765 pound-feet of torque was scarcely challenged for the job, and its 397 horsepower easily enabled the rig to maintain freeway speeds, even uphill. The long wheelbase and three-quarter-ton chassis kept everything stable as a rock. We made one 60-mile run on the dark, rainy, and winding freeway and felt totally secure. 

Both 6-speed automatics offer a Tow/Haul mode that will execute downshifts with throttle blipping to maximize engine braking. In most cases Tow/Haul is designed for optimum use with loads of 70 percent-or-more of maximum GCWR, though you won't hurt anything by using it with lighter trailers or not using it with heavier trailers. 

The gasoline engine is the purchase-cost choice and best used when routine heavy towing or high mileage are not on the agenda. Opting for the $100 numerically higher 4.10:1 axle ratio is worth every penny and raises the tow rating considerably (it will likely be standard in 2014). We saw a bit more than 12 mpg on a highway leg in an unloaded 2500-series gas engine. 

Buyers who tow many miles should strongly consider the diesel, which delivers twice the torque output and notably better fuel mileage and work ratings. The Duramax diesel is relatively quiet. As with all HD pickups and sport-utes the Duramax uses DEF for the emissions system. This is filled underhood and may need to be done only at service intervals but is available at fuel depots and parts stores if you drive hard, in scorching hot weather or idle excessively. Running out will not stop the truck, but if you ignore warning messages it eventually will not restart. 

Pickups of yore tended to buck like broncos on turnpike expansion joints and other uneven surfaces, with the bed trying to bounce one direction and the cab the other. Often a function of wheelbase, this can't be completely eliminated in a long vehicle like a Sierra HD, but it does an admirable job of mitigating the motion. Longer cabs get special body mounts to aid in that regard, though we found the regular cab gave a good accounting of itself; with the diesel's 700-mile-empty claimed range, it's entirely possible a base manual seat would wear you out before any ride issues did. 

There's heft to the feel of a Sierra, from the way it takes big bumps to the steering and throttle inputs but this should not be construed as effort on the driver's part. Its handling characteristics are benign and amount to basic plowing if you push too hard. All-terrain tires give better grip on dirt roads, at the expense of steering precision and noise on paved roads. Optional 20-inch wheels look good but we prefer 17- and 18-inch wheels for numerous reasons, including ride and replacement cost. 

The Sierra HD uses disc brakes with ABS, and independent front suspension. Of the full-size ?-ton pickups, only the GM heavy-duty pickups use the same design on 4WD models as on 2WD versions. This means the 4WD HD models from GM have a lower nose and more responsive steering than their four-wheel-drive Ram and Super Duty counterparts. Again, like any big pickup, the tail is prone to kick over impacts with an empty bed; the Sierra is similar to others although it may feel it has more kick because the front is softer. Apart from turning circle and size, it takes no more effort to drive the Sierra HD than to drive any other GMC. 

The rearview mirror camera display gives the same view as a navigation-screen version except on a smaller scale. Hooking up a trailer is a piece of cake: Watch the hitch ball in the mirror screen, and when the last glint of chrome disappears under the trailer hitch, you're perfectly aligned. This is easier in shade than direct sunlight, especially with predominantly white trailers, and you might tilt the mirror down to stop glare from obscuring the image. Makes you wonder how you ever got along without it. With navigation you get a much bigger rearview camera image, which makes it easier to spot objects and line up the hitch ball. 

The optional rear park assist gets fooled by a slide hitch, however, and repeatedly flashes a message that it's disabled, and to see owner's manual. It's surely something you can override, but we just cleared the message each time. 

Don't count on the camera for backing up with a trailer, though. When you can see your trailer, the old-fashioned way of looking in the mirror or over your shoulder is easier. When you can't see the trailer, for example an empty boat trailer or car-hauler like ours, the camera is deceptive, because the lens is so wide. When the trailer veers, you can't even tell in the camera. 

The optional integrated trailer brake controller will apply your trailer brakes smoother than any aftermarket controller and works in concert with the Sierra's braking system. Be sure to get this feature. 

The diesel engine has an exhaust brake function in the turbocharger, and the Allison transmission uses grade control logic to help maintain chosen speeds, even using cruise control on up- and down-grades. 

Note that, as on any pickup, the maximum ratings usually don't apply simultaneously. While a particular Sierra HD might carry 7200 pounds or tow 23,000 it can't do both at the same time without substantially exceeding the GCWR. 

Summary

If you want the capability of a big pickup with the least sensation of driving a big pickup, the Sierra HD deserves consideration. In a world run amuck for ever-larger trailers and powerplants, it's a sensible alternative for anyone who needs to haul heavy material. 

G.R. Whale filed this report to NewCarTestDrive.com from Flintstone, Maryland. 

Model Lineup

GMC Sierra HD Regular Cab 2500 2WD WT ($29,550), Extended Cab 2500 2WD SLE long bed ($36,390), Crew Cab 3500 4WD DRW WT ($36,330), Extended Cab 3500 2WD SLT ($42,915), Crew Cab 3500 4WD SLT ($47,750), 3500 Denali 4WD ($50,740). 

Assembled In

Fort Wayne, Indiana; Flint, Michigan. 

Options As Tested

navigation ($2,250); power slide rear window ($250); 20-inch forged polished aluminum wheels ($850).