2008 GMC Sierra 3500HD Reviews and Ratings

Extended Cab SLT 2WD

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2008 GMC Sierra 3500HD
G.R. Whale

GMC Sierra heavy-duty pickups are well-suited for real-world use and abuse. They can haul tons of brick and cement and tow the mixer, 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. The Sierra HD models are the mid-level part of GMC's truck lineup, so if your hauling happens once or twice a year, or you tow a bass or ski boat, the 1500-series is better-suited; conversely, if you've got a mammoth trailer to pull, step up to the Kodiak/Top Kick medium-duties.

The GMC Sierra HD pickups were thoroughly redesigned for 2007, so changes for 2008 are limited to smaller items like seat adjusters, gauges, and adding XM Satellite Radio capability.

The GMC Sierra HD offers styling unique to GMC, so it's not just a Chevy Silverado with a different grille.

As with all heavy-duty pickup lines, the Sierra HD offers plenty of configurations with three cab sizes and two bed sizes in 2WD or 4WD. But it also offers two separate interior concepts, something the other guys can't match. And GM offers the only HD pickup with a six-speed automatic as standard (an option only on the Dodge Ram diesel). Its standard 6.0-liter gas V8 is rated higher than anyone else's, as is the 6.6-liter diesel. And only GM includes OnStar as standard.

Almost everything you can get in a GMC sport-utility is available here, including a subwoofer-equipped sound system, navigation, driver memory system, heated leather seats (and heated windshield washer fluid) and a moonroof. At the other end of the spectrum, for the entry price of around $24,000 you get a functional pickup with real load-carrying ability and all the safety bits of the top-line model.

The trick in buying a 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 $24,000 to well past double it. Model Lineup
The 2008 GMC Sierra HD comes in three cabs (Regular Cab, Extended Cab, Crew Cab) and two weight classes, 2500 HD and 3500 HD, all with 2WD or 4WD. The 2500 (sometimes called 3/4-ton) offers two pickup box sizes, while the 3500 (1-ton) is eight-foot box only. If you wish to add your own utility box or flatbed, cab and chassis models are offered.

GMC nomenclature labels trim levels as commercial-grade Work Truck, popular SLE (1 and 2), and premium SLT that resembles a Yukon sport-utility up front.

Basic WT fare includes a split vinyl bench seat (and split rear seat on four-door cabs), stereo radio with XM satellite, air conditioning, six-speed automatic transmission, tire pressure monitors, and ABS.

Mid-level SLE models include all basic equipment and add cruise control, chromed steel wheels, electronic shift for 4WD, auto-dimming mirror and compass, driver lumbar, locking seat cushion storage, and leather-wrapped steering wheel. The SLE2 package adds fog lamps and interior upgrades such as cloth-upholstered power-adjustable front seats and redundant controls on the steering wheel.

SLT badges are reserved for the priciest Sierras, those with an interior modeled after GMC luxury utilities. These include as standard leather upholstery with 12-way power and heated front seats, two-person driver memory, heated windshield washer fluid system, locking differential, remote start, towing package, 17-inch aluminum wheels, and a Bose audio system with subwoofer.

Base power for all GMC HDs is the latest 6-liter V-8 with an iron block for durability and variable valve timing for efficiency; it rates 353 hp and 375 lb-ft of torque (312 hp for GVWR above 10,000 pounds). The sole option is a 6.6-liter Duramax turbodiesel, at 365 horses and 660 lb-ft of torque. A six-speed automatic is the only transmission offered, and on diesels it adds $1,200 to the engine's roughly $7,200 tab.

Sierras can be set up for anything from a night on the town--moonroof, satellite radio, navigation--to a year on the ranch or fleet garage with snow plow prep, integral trailer brake control, remote start, and power takeoffs. Determining exactly the right model and options will take careful and honest shopping because of the sheer number of choices.

Safety equipment includes frontal airbags, front seat belt pretensioners (a first for HD pickups), ABS, and OnStar. Walkaround
Although the Sierra HD shares its mechanical bits with Chevrolet's Silverado HD, they are no longer visual clones. A higher grille between the stacked headlights lead to a flatter, more traditionally styled hood than the Silverado, and the GMC gets unique fenders, lamps and box sides as well. For this new generation the Chevy Silverado and GMC Sierra do not share near-identical appearance. A new panel forming process gives the dually models integral, seamless fender flares and smoother finish for improved paint.

The wallpaper sized, ruby red GMC logo makes its origin plainly obvious but the bumper that blends into the fenders gives a much cleaner look and is unusual in HD pickups. Increased frame stiffness allows a smaller gap between the cab and body, and combined with the more aerodynamic windshield and narrower door gaps, makes the Sierra much quieter than its predecessor.

The box sides are deeper by an inch-and-a-bit, the tailgate has a optional lock and assist for closing it with less effort, and the cargo management option fits rails to three sides of the bed; these can be used for tie-down points and to carry a variety of tool or utility boxes. The stoutest Sierra HD's can tow 13,000 pounds with the new 2.5-inch receiver hitch, and the new dual-element mirror and trailer brake control options will lower the stress level.

Most HD pickups have external dimensions close to each other and the Sierra is similar; more than six-and-a-half feet wide outside and room for a 4x8-foot sheet of building material to ride flat in the long bed. In 4WD versions the Sierra is slightly lower than competing pickups, and that inch or two could make the difference in commercial garages or fifth-wheel/bed clearance. Interior
The high-line Sierra SLT cabin feels just like a large luxury car, with a low-profile dash sporting lots of woodgrain trim, a compact instrument cluster with better graphics for 2008, 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 is very low-profile, sleek, and speaks of good fit and finish. All other models use a more conventional 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.

Perhaps not as stylish as the SLT's, the standard dash is the more functional of the two and equally well assembled (and gets the same improvements). 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 and is offset slightly from the seat centerline.

A regular cab has room for a XXL-sized gent and space behind the seat for his coat and boots. Extended cabs have articulated side doors that swing 170 degrees for easier loading, the windows in those doors roll down flush, and the seat cushion folds up for more storage. 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. Note that the sunroof shade on high-line versions is literally a shade (like that on a Mini) and not a solid cover, and the interior will warm faster on sunny days.

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 it is the quantity of similarly-shaped and labeled small buttons that butterfingers may have some issues with. Door switches have been revised so your guard dog won't wind the window up, but he may still lock you out; fortunately, OnStar (and the turn-by-turn navigation it offers) is standard and includes a few months free service.

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. Apart from turning circle and size, it takes no more to drive this than to drive any other GMC. Driving Impressions
When it was re-engineered for 2007, the GMC Sierra raised the bar in ride quality and refinement, and minor upgrades for 2008 improve on that. It will not ride like a car, nothing that can carry a car does, but it may spoil you for a pickup.

With many models over 7,000 pounds empty, the Sierra HD is a lot of mass to move around, and while the new 6-liter has broadly the same horsepower as the old big-block, torque is down roughly 80 lb-ft. Torque is what gets any load moving, up to about 45 mph, and helps keep it moving on grades. However, the six-speed transmission makes up for a lot, so the absence of a big-block is most noticed in low-range 4WD and the less-forceful shove in your back when you leave a traffic light. The 6.0 and six-speed automatic will do about 90 percent of what the 8.1-liter did, and generally use a bit less gas in the process. Remember however, that horsepower on the dual-rear wheel 3500 6.0 is lowered to 312 hp, making an even better argument for the diesel.

With 660 lb-ft of torque available at a much lower engine speed and 365 hp, the Duramax turbodiesel option blows the 6-liter into the weeds for pulling power and fuel economy, though you might say at $8400 for the powertrain it ought to. Much of the added expense from last year is due to the new emissions requirements for diesel engines, reductions of 90 percent in some cases, and the diesel exhaust pipe stays clean and steel-colored inside where the gas engine's is black. The next generation of induction systems has also made the diesel much quieter; your riders may not know it's a diesel if you don't tell them.

Pickups of yore tended to buck like broncos on uneven surfaces like turnpike expansion joints, 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.

There's heft to the feel of a Sierra, from the way it takes big bumps to the steering and throttle inputs. 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 tarmac.

Like all big 2WD pickups the Sierra uses all-vented disc brakes with ABS, and independent front suspension. However, only the GM heavy-duty pickups use the same design on 4WD models, giving them a lower nose and more responsive steering. 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.

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. This controller, however, is not compatible with all brands of electric-hydraulic disc brakes becoming more common on high-end RVs.

The 2.5-inch receiver hitch allows conventional trailer ratings to 13,000 pounds, higher than many competitive offerings; the maximum for fifth-wheels 16,700 pounds. The strongest Sierra HD will haul 23,500 pounds gross combined: the truck, fuel, passengers, cargo, and trailer. 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 stuff but doesn't want a special driver's license to do it.

G.R. Whale filed this report to NewCarTestDrive.com from California.

Model as tested
GMC Sierra 3500 HD Crew Cab 4x4 6.6 auto ($39,310)
Basic Warranty
3 years/36,000 miles
Assembled in
Pontiac, Michigan; Flint, Michigan
Destination charge
Gas guzzler tax
Base Price
Price as tested
Options as tested
6.6-liter diesel ($7195); Allison automatic ($1200); EZ tailgate ($95); HD trailer package ($230); cargo management ($95); radiator cover ($55)

Model Line Overview
Model lineup
GMC Sierra HD Regular Cab 2500 4WD WT ($26,930), Extended Cab 2500 2WD SLE2 long bed ($32,300), Crew Cab 3500 4WD DRW WT ($32,885), Extended Cab 3500 DRW 4WD SLT ($38,175)
Safety equipment (standard)
frontal airbags, front seat belt pretensioners, ABS, OnStar
Safety equipment (optional)
6.6-liter ohv 32-valve V8 turbodiesel
6-speed automatic

Specifications as Tested
air conditioning, power steering, power disc brakes, locking differential, tire pressure monitors, Autotrac electric-shift 4WD, power heated mirrors, power windows, power locks, overhead console, cruise control, tilt leather wheel, driver info center, CD/MP3 audio, tap-shift automatic, fog lamps, aluminum wheels

Engine & Transmission
6.6-liter ohv 32-valve V8 turbodiesel
Drivetrain type
4-wheel drive
Horsepower (hp @ rpm)
365 @ 3200
EPA fuel economy, city/hwy
Torque (lb.-ft. @ rpm)

Brakes, front/rear
vented disc/vented disc with ABS
Suspension, front
independent, torsion bars
Suspension, rear
solid axle and leaf springs

Seating capacity
Head/hip/leg room, middle
Head/hip/leg room, front
Head/hip/leg room, rear

Fuel capacity
Trunk volume
Turning circle
Towing capacity
Track, front/rear
Ground clearance
Curb weight

J.D. Power Rating
Overall Quality Not Available
Overall Quality - Mechanical
Not Available
Powertrain Quality - Mechanical
Not Available
Body & Interior Quality - Mechanical
Not Available
Features & Accessories Quality - Mechanical
Not Available
Overall Quality - Design
Not Available
Powertrain Quality - Design
Not Available
Body & Interior Quality - Design
Not Available
Features & Accessories Quality - Design
Not Available

Overall Dependability Not Available
Powertrain Dependability
Not Available
Body & Interior Dependability
Not Available
Feature & Accessory Dependability
Not Available

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J.D. Power Rating Legend
Among the Best
5 / 5
Better than Most
4 / 5
About Average
3 / 5
The Rest
2 / 5

* The J.D. Power Ratings are calculated based on the range between the car manufacturer or car model with the highest score and the car manufacturer or car model with the lowest score. J.D. Power generates a rating of a five, four, three, or two. If there is insufficient data to calculate a rating, “Not Available” is used in its place.

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