For the last decade or so, the heavy-duty truck market has been full of competitive spirit, with each automaker churning out a new technology or powertrain that oneups 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 ¾-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 optionladen trim levels and body styles.
To find out how well it works in regular use, GMC hosted us in Jackson Hole, Wyoming, where we got to sample the 2020 Sierra HD in some surprisingly rugged and taxing situations.
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 and 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.
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 driveability nor capability suffer 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.
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. 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.
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January - February 2020