We just traveled to Jackson Hole, Wyoming to test drive the all-new 2020 GMC Sierra HD, the mechanical twin to the 2020 Chevrolet Silverado HD. While identical in terms of its architecture and drivetrain, the two heavy duty GM pickups have never been so different, with the Sierra offering different styling, exclusive options and technology, such as the AT4 HD off-road variant, a carbon fiber bed and an innovative multi-function tailgate GMC calls MultiPro.
But behind all that sits one of the most accomplished work horses to date. As a matter of fact, General Motors brags about having the strongest trucks in the segment with a 35,500 pound towing rating when powered by the 6.6L L5P V8 turbodiesel Duramax engine and equipped with the ten-speed automatic “Allison” transmission. The combination makes 445 horsepower and 910 pound-feet of torque.
By comparison, the 2019 Ram Heavy Duty maxes out at 35,100 pounds while the current Ford Super Duty hauls 32,500 pounds. That said, Ford should soon release the specs of its updated 2020 Super Duty, which should crank up the towing capacity to better compete against the new GM Heavy Duty bruisers.
To prove just how capable its new mule is in towing, GMC had prepared two different towing activities for us. The first consisted of hauling a 20,000 pound trailer with a Sierra HD AT4 single wheel on a 15-mile trek through Wyoming’s winding and ascending. During that run, we would be able to assess the truck’s performance during prolonged periods of real-world towing, which also allowed us to sample the truck’s new towing camera system.
Side and rear mounted cameras allow the pilot to carefully monitor the trailer directly from the Sierra’s infotainment screen. There’s even an optional trailer-mounted camera which allows us to see straight through the trailer, and onto the road behind it.
The second towing exercise had us hitch a Big Tex Heavy Duty gooseneck trailer onto a dual rear-wheel Sierra Denali 3500HD. That trailer, weighing in at 30,000 pounds, had a bunch of the competition’s tailgates stacked up onto it, a reference to GMC’s Multi-Pro tailgate commercial. It’s important to note that the GM’s claimed 35,500-pound towing rating can only be achieved with a Regular Cab, dual rear-wheel 3500HD.
In both occasions we were impressed by the smoothness under towing exhibited by the 2020 GMC Sierra HD. Not only did the big rig seem unbridled by the massive weight hanging behind its bed, but cabin vibrations and secondary motions were kept low, to the point that we quickly forgot we were actually pulling something.
Furthermore, the ten-speed gearbox did a fantastic job of finding the right gear for the task. In some cases, it even allowed itself to downshift smoothly during steep inclines.
Another stand-out characteristic is how linear the Duramax’ power delivery is under load. There’s very little indication of turbo lag, which is much more noticeable in oh… say… a Ram with a Cummins engine. The 2020 GMC Sierra HD delivers ample acceleration, even while carrying a load the size of a small house.
While GMC still needs to do something about its interiors, we must admit we were thoroughly impressed by what this big guy can do during towing. We still need to pit it directly against its main rivals in similar conditions for a proper assessment of its capabilities, but judging from our first drive of the 2020 GMC Sierra HD, we feel General Motors has already won the Heavy Duty war.