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First Drive: 2020 GMC Sierra HD

Riding Heavy in GMC’s New Sierra HD

Aug 25, 2019
Photo 2/28   |   2020 Gmc Sierra Hd Exterior Front Quarter Towing 01

For the last decade or so, the heavy-duty truck market has been ripe with competitive spirit, each automaker churning out a new technology or powertrain that one-ups the others in some way. However, with a few exceptions, General Motors has been content to watch Ford and Ram return volley for volley—sitting out on the max-towing measuring contest specifically. That changes with the all-new 2020 GMC Sierra HD, available as always in -ton 2500HD and 1-ton 3500HD variants.

Thanks to a completely redesigned platform, suspension, and drivetrain, the new Sierra HD can haul a trailer weighing up to 35,500 pounds, pole-vaulting over the 2020 Ram Heavy Duty and 2019 Ford F-Series Super Duty. What's more, all dual-rear-wheel/Duramax diesel configurations can tow at least 30,000 pounds, even in heavier, more option-laden trim levels and bodystyles.

To find out how well it works in regular use, we headed to Jackson Hole, Wyoming, where we got to sample the 2020 GMC Sierra HD in some surprisingly rugged and taxing situations.

Photo 3/28   |   2020 Gmc Sierra 3500hd Dually Exterior Front Quarter Towing 01

Towing Truths

The 2020 GMC Sierra HD is available with two powertrains, an all-new 6.6L gasoline V-8 paired to a six-speed automatic transmission or the carryover Duramax L5P 6.6L turbodiesel V-8 mated to an all-new Allison-branded 10-speed auto. We spent the vast majority of our drive time behind the wheel of diesel-powered pickups, and while the GMC brings up the rear in terms of maximum available torque among big trucks, we found very little to complain about.

Photo 4/28   |   2020 Gmc Sierra 3500hd Dually Exterior Rear Quarter Towing 01

Yes, that's true. At 445 hp and 910 lb-ft of torque, the once-champion L5P Duramax V-8 comes up short on the 2019 Super Duty's Power Stroke diesel by 20 lb-ft and the 2020 Ram Heavy Duty's Cummins diesel by 90 lb-ft, but neither drivability nor capability suffers for it. GM gave the 2020 GMC Sierra HD substantially more robust drivetrain components and that aforementioned Allison 10-speed gearbox, which allows engineers to avoid the temptation to torque-manage the Duramax in First and Second gears. That means the driver gets the full brunt of torque right off the line—the same can't be said of Ram and Ford. The net effect? Faster acceleration and passing while towing, says GMC.

Photo 5/28   |   2020 Gmc Sierra 3500hd Dually Exterior Front Quarter Towing 02

We're inclined to agree. The Duramax V-8 simply shrugs off complex driving maneuvers, even when towing a 14,000-pound car hauler over the twisty, steep U.S. Route 89/26 between Jackson Hole and Alpine. In these situations, the bumper-pull trailer made its presence known, but it never felt close to taxing that specific truck's abilities (it was a Sierra 2500HD AT4).

We were able to execute relatively swift passing maneuvers in some of the highway's four-lane sections, and our speed never dropped below the route's 55-mph limit if traffic ahead allowed it. On grades, the Allison transmission downshifted multiple gears smoothly, keeping the Duramax on boil and ready to act. The whole powertrain package faded into the background while towing, simply doing its job well and without calling any attention to itself.

Photo 6/28   |   2020 Gmc Sierra Hd At4 Exterior Towing 01

That particular single-rear-wheel Sierra towing experience represents one of GMC's other bragging rights, the towing capacity of its available AT4 off-road trim level. The Sierra 2500HD AT4 can lug up to 18,500 pounds, with a maximum payload of 3,615 pounds. That's not bad for an off-road pickup, although let's just get one thing straight right now: GMC kept comparing its capability ratings to those of the Power Wagon.

To be fair, that version of the Ram 2500 has surprisingly low numbers. 1,660 pounds of payload and 10,620 pounds when towing are the purview of -ton trucks these days. But the Power Wagon offsets these relatively unimpressive stats with stellar suspension articulation and incredible off-road capability that the AT4 just can't match. So while the GMC might be a more well-rounded off-road package that trades off some ruggedness in the name of capability, it definitely wouldn't keep up with a Power Wagon in Moab or on the Rubicon Trail.

Photo 7/28   |   2020 Gmc Sierra Hd Exterior Side View Towing

We also availed ourselves to haul a less weighty fifth-wheel camp trailer behind a dually Sierra Denali 3500HD, which cosseted us in complete comfort while handling the load confidently. The 3500's stiffer suspension made its presence known with a slightly busier ride, but it wasn't untoward given what we knew the truck could handle. At one of our pre-determined rest points, GM hitched a 30,000-pound trailer to the same truck configuration, which we were able to sample on Wyoming's public roads. Our short drive loop proved the truck to be able to fit in with traffic, even when hauling such a massive trailer. While acceleration and braking were justifiably dulled (30,000 pounds is a lot of weight, people), the truck's stout basic structure and overall performance promise good things for those who make a habit of towing big trailers.

Better Living Through Technology

Each of our well-equipped Sierra Denali and AT4 test vehicles were fitted with GM's comprehensive suite of cameras that offer a class-leading 15 different views for greater confidence while towing. What's more, some of these views can be permanently displayed on the center stack, including a helpful lane-minder that shows how the rear wheels and trailer are tracking on either side of the truck. A useful "transparent trailer" mode makes use of an accessory camera mounted to the rear of a bumper-pulled box trailer, stitching together different camera views to provide a panoramic view of traffic or obstacles behind the trailer. It proved hugely useful in lane changes, and we can imagine its helpfulness while reversing (which we avoided doing as much as possible).

Photo 8/28   |   2020 Gmc Sierra Hd Cameras Transparent Trailer View

Other tech features included in the 2020 GMC Sierra HD are bundled into its "ProGrade Trailering System" suite. An infotainment system trailering app provides a trailer light test feature and trailer electrical system diagnostics, and an available automatic electric parking brake automatically applies the brake when hitching to prevent that annoying inch or two of rollback that can foul up an approach. A hill-hold system also prevents the truck from rolling back when starting from a stop on a grade, providing a stable towing experience. And GM's trailering label, placed on the driver's door jamb, provides VIN-linked towing and payload information that takes each specific truck's options and curb weights into account—no more guesswork using the vehicle's general towing guide.

Photo 9/28   |   2020 Gmc Sierra Hd Exterior Jackson Hole

The net effect is a comprehensive, confidence-inspiring towing experience. We at Truck Trend are no strangers to hauling a heavy trailer, but we can't recall a truck whose technologies added as much real-world use as the Sierra HD. We particularly appreciated the camera modes, allowing us to place the trailer exactly within the lane lines with more precision than what's offered by the goofy-looking (but useful) towing mirrors. One surprising feature is a side-biasing mode that detects steering input while towing at slow speeds, then automatically pulls up that camera view on that side to prevent accidental curb checks or worse. And even if the vehicle's infotainment display is on a different screen, activating the turn signal while towing will automatically pull up the lane-monitoring camera to allow the driver to check his or her blind spot more accurately. It was all surprisingly useful without feeling gimmicky or like we were being nannied by electronics.

Photo 10/28   |   2020 Gmc Sierra Hd Exterior Front Quarter 01

HD-Specific Styling

To many truck buyers, capability and the driving experience are the highest priorities. Thankfully, the 2020 GMC Sierra HD also bundles attractive styling into the mix. The HD's design is inspired by the new-for-2019 Sierra 1500, but surprisingly, it doesn't share a single, readily visible body panel with its little brother, not even the doors or bed.

Photo 11/28   |   2020 Gmc Sierra Hd Exterior Front View 01

In fact, the Sierra HD features deliberately fewer body creases and side surfacing features than the 1500, partly because GM knows its heavy-duty customers frequently apply advertising or company liveries to their trucks, and the flatter bodysides make that practice easier. As such, the truck is substantially blockier than its light-duty sibling, a trait amplified by the Sierra HD's bigger, bolder front end.

We were also surprised to learn that the 2020 GMC Sierra HD also comes with a completely different bed structure than the 1500. Relative to the -ton, the HD's bed is actually shallower and offers less total cubic feet of space, a conscious decision on GM's part because it results in lower bodysides that aid bedside access and prevent damage when hitching a gooseneck or fifth-wheel trailer. There's still plenty of room back there for stuff, and a total of 16 tie-down points make securing that stuff much easier. GMC also offers an excellent, HD-specific MultiPro tailgate on the Sierra HD, along with standard enlarged bumper corner steps and HD-specific bedside steps. Thoughtful touches like these help set the truck apart from its predecessors and competitors.

Photo 12/28   |   2020 Gmc Sierra Hd Exterior Rear Quarter 01

Hitting the Road

Whether unloaded, saddled with payload, or towing a trailer, the 2020 GMC Sierra HD offers a pleasant ride, with its stiff and stout structure swiftly absorbing road imperfections with less cowl shake or bed jiggle than the outgoing truck. Extensive acoustic tuning also reduces road noise to a whisper, improving on GMC's already impressive predecessors to provide a tranquil driving environment that reduces driver fatigue.

Photo 13/28   |   2020 Gmc Sierra Hd Exterior Rear Quarter 02

Unloaded, it's easy to feel all 910 lb-ft of torque making its way through the drivetrain. Prurient wheelspin is a toe-twitch away, and passing on two-lane roads is a non-event. Even with a 3,000-pound payload of logs, the Sierra HD's Duramax V-8 offered nothing but power in reserve, meaning we could put a pesky dawdler in our rearview mirror with nary a thought. With cruise control set at 65 mph, the 2020 Sierra offers a hushed, tranquil driving experience that should be at or near the top of its class.

Photo 14/28   |   2020 Gmc Sierra Hd Interior Cabin

Balance and Poise?

Complaints? Sure, we've got a few, but most of them involve the already dated and low-quality interior that we've bled enough ink on, so we'll withhold them for now. (Besides, we hear the stellar 2019 Ram 1500 and 2020 Ram Heavy Duty have put the fear in God in GMC's interior designers—rumor has it an emergency refresh is on its way for 2021 or 2022.) Otherwise, GM-signature numb and light steering are on full display here, the center console should have more storage than it does, the Denali HD Duramax's busy front styling could use some toning down, and seriously, where's the adaptive cruise control?

Photo 15/28   |   2020 Gmc Sierra Hd Exterior Rocker Panels

Beyond those niggles, the 2020 GMC Sierra HD offers an excellent driving experience, confident and convenient towing doodads, a segment-exclusive camera system, the surprisingly useful MultiPro tailgate, and a holistic powertrain package that just works. Taken as a whole, the GMC is a self-assured companion and ideal road-trip sidekick, giving HD-truck novices and veterans alike plenty to appreciate about the capable and comfortable truck.

Photo 16/28   |   2020 Gmc Sierra Hd Exterior Front Quarter 02

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