The Sierra HDs start with a sturdy foundation - a fully-boxed ladder frame with an independent front suspension and asymmetrical leaf springs holding on a solid axle out back. Those underpinnings are clothed in imposing new sheetmetal - including a blunt, chrome-laden grille and squared-off fenders - that signals these trucks mean business. Steps mounted in the rear bumper along with reworked stake holes make it easy to climb into the bed, while an easy open/close option allows the tailgate to be accessed using just a pair of fingers.
As one would expect, the 2500HD and 3500HD are differentiated mainly in terms of capability, with the latter being stronger and offering the option of a foaur-rear-wheel "dually" setup. Both offer standard and long beds - measuring 6.57- and 8.17-feet, respectively - along with a choice of Regular Cab (two doors, single row of seating), Double Cab (four doors, two rows) and Crew Cab (four doors, more space for rear passengers).
The two models also share a powertrain range, which starts off with a gasoline 6.0-liter V8 that produces 360 horsepower (322 in the 3500HD) and 380 lb-ft of torque. Linked to a six-speed automatic gearbox, the 6.0-liter sends power to a 4.10 rear axle that enables maximum conventional towing capacity of up to 13,000 lbs. for the 2500HD and 14,200 lbs. for the 3500HD. Buyers of the 2500HD enjoy payload capacity of 4,306 lbs., while the 3500 tops out at 7,374 lbs.
An optional version of the 6.0-liter is capable of running on either compressed natural gas (CNG) or gasoline thanks to hardened valves and valve seats. Its towing and payload ratings are similar to those of the standard engine, though power drops to 301 horsepower and 333 lb-ft of torque when running on CNG.
The HDs' range-topping engine is a 6.6-liter Duramax turbodiesel V8 that churns out 397 horsepower and a massive 765 lb-ft. of torque. The oil-burner is linked to a heavy-duty six-speed automatic gearbox built by transmission expert Allison, enabling tow ratings of up to 14,500 lbs. for the 2500HD and 19,600 lbs for the 3500HD. In terms of payload, the 6.6-liter-equipped 2500HD can handle 3,501 lbs., and the 3500HD is good for 5,817 lbs.
All HDs come standard with rear-wheel-drive, but four-wheel-drive (or, for dualies, six-wheel-drive) is optional, as is a gas-saving 3.73 axle.
The Inside Story
The latest refresh brought a much more refined interior to the HDs. Sharing much with the light-duty Sierra 1500, the cabin features a clean, modern dashboard with durable yet appealing materials, a central 4.2-inch display or 8.0-inch touchscreen (depending on trim level), and USB, AUX and SD card inputs.
All HDs except the base model are equipped with GMC's IntelliLink infotainment system, which integrates entertainment and navigation functions (when equipped), and also offers access to smartphone-based apps like Pandora radio and Stitcher radio.
The system can be controlled through dashboard knobs, steering wheel buttons or the eight-inch touchscreen, and there's also a voice recognition system for hands-free calls, destination entering, song selection and more. Its "natural language" functioning can recognize a staggering number of phrases - effectively eliminating the need for the clunky and cumbersome memorized commands.
New inlaid, triple-sealed doors cabin ensure that the cabin is sufficiently quiet for even whispered voice commands.
HD buyers looking for an extra dose of style and luxury can opt for the Denali model. Outside, the Denali package entails a classy chrome grille, body color bumpers and special LED running lights. Inside, there's soft-touch instrument panel trim, aluminum trim, Denali badging and numerous standard niceties, including heated and ventilated front seats, a Bose audio system, a navigation system and more.
Trim Level Breakdown
The Sierra 2500HD and 3500HD are available in eponymous base model, SLE, SLT and Denali trim levels.
The no-nonsense, work-truck-grade base model comes standard with A/C, power windows and locks, a six-speaker AM/FM stereo with 4.2-inch display screen, USB and AUX inputs, an SD card reader, cruise control, cloth upholstery, vinyl floor covering and 17-inch painted steel wheels.
To those features, the SLE adds or substitutes GMC's IntelliLink infotainment system, a 4.2-inch instrument cluster display screen, a rearview camera, a CD player and SiriusXM satellite radio, Bluetooth connectivity, a leather-wrapped steering wheel with audio controls, sun visor vanity mirrors, interior carpeting, remote keyless entry, heated and power-adjustable exterior mirrors, an EZ-lift and lower tailgate, and 17-inch machined aluminum wheels.
The SLT brings heated front seats, an upgraded version of IntelliLink with an 8.0-inch touchscreen, dual-zone automatic climate control, remote start, a 110-volt power outlet, a universal garage remote, an anti-theft system, an auto-dimming interior rearview mirror, a power rear sliding window, additional exterior chrome trim, fog lights and 18-inch forged aluminum wheels.
The range-topping Denali includes leather upholstery, heated and ventilated front seats, a heated steering wheel, a navigation system, a Bose premium audio system, power-adjustable pedals, and unique trim inside and out.
A wide range of options packages is available for all trim levels.
The base model and SLE can be spruced up with the Convenience Package, which adds keyless entry, tinted windows, heated and power-adjustable exterior mirrors, LED cargo box lighting and a 110-volt power outlet. The SLE offers the Preferred Package, which it builds on those features with a power-adjustable driver's seat, MyLink with 8.0-inch touchscreen, rearview camera, remote start, dual-zone automatic climate control and a rear window defogger. The SLT can be spec'd with its own Preferred Package; it adds a heated steering wheel and front and rear park assist.
Those looking to go off the beaten trail should opt for the Off-Road Suspension Package. Offered on the SLE and SLT, it includes 46mm high-pressure gas-charged shocks, a 36mm front stabilizer bar, off-round jounce bumpers, an underbody transfer case shield, high-capacity air cleaner, hill descent control, unique Z71 badging and decals, model-specific interior and exterior trim elements and either 17-inch (SLE) or 18-inch bright machined wheels.
The base model, SLE and SLT can be fitted with the Chrome Appearance Package, which adds a polished exhaust tip, chrome tow hooks and chrome tubular assist steps.
Available on the SLT and Denali, the Driver Alert package includes lane departure warning, forward collision alert, a safety alert seat and front and rear parking assist.
The Sierra 3500HD come standard with dual front airbags in addition to traction and stability control systems. The 2500HD adds standard dual side and side curtain airbags, which are optional on the 3500HD.
Several new optional safety features are also available for both trucks. A lane departure warning system alerts the driver should the Sierra begin to drift into an adjacent lane, and a forward collision alert system provides a warning if it detects an imminent collision with a vehicle or object up ahead. Notably, warnings can be conveyed via audible alarms or, more subtly, by a vibrating driver's seat.
In the market for a pickup that can basically tow a semi-trailer? Besides the Sierra HDs, your options include the Ford F-Series Super Duty and Ram's own HD trucks.