On a recent trip to Wyoming for a GMC national drive event Automotive Fleet was able to drive the 2020 GMC Sierra HD diesel and tow nearly 13,000 pounds over a long path, and overall impressions of the truck are positive.

It was hard not to enjoy driving the Sierra HD: a max tow rating of 35,500 lbs. means that it handled everything that we threw at it during the event with minimal effort and a suite of technology offerings made the towing experience mostly stress free, even with minimal towing experience.

For our Sierra HD driving experience, GMC attached a nearly 13,000 lb. Keystone Camper to the back of the truck and sent us on our way through the scenic mountain roads of Jackson Hole, Wyo.

Towing Capability

The most impressive part of towing the camper was that when the truck reached a cruising speed, it didn’t really feel like we were towing nearly 13,000 lbs.; although, with the Sierra HD diesel’s max towing capability of 35,500 lbs. (52% more than previous generation) that shouldn’t have been too surprising.

Even with that much weight attached, the Sierra HD confidently handled going uphill, the truck never really felt like it was exerting itself to handle the task. Going downhill, an exhaust brake button allowed us to choose whether the truck would help with braking. I tried going downhill without the exhaust brake on but quickly went back to driving with it on, as the difference with and without it on was stark.

With the exhaust brake on, it felt like the truck was ensuring a proper descent speed on its own and I rarely had to manually apply the brakes. With the exhaust brake off, going downhill was a much more involved process.

Apart from the truck assisting the driver while going downhill, the Sierra HD also includes a park grade hold assist that enhances its hill hold assist by using all four tires to keep the truck in place. GMC stated that this reduces strain on the transmission and prevents sliding for a smoother experience when shifting in and out of park.

Off the line, the truck hardly struggled to get to speed. You felt that there was weight behind you, but it simply didn’t take long for the truck to reach speed, and from there it was smooth sailing.

This off-the-line experience is partly thanks to the fact that General Motors has engineered the HD’s 6.6L Duramax turbo diesel engine and Allison 10-speed transmission to provide all of its 910 lb.-ft. of torque in first gear.  

With an 18,000 lb. trailer attached, GMC stated that it would take its Sierra HD 19.9 second to go from 0-60 mph; 18.2 seconds to go from 25-60 mph; and 11.8 seconds to go from 40-60 mph on a flat path.

On a separate day we drove the Sierra HD with 2,000 pounds of wood logs in the box. At the end of the drive I had nearly forgotten that they were there.

One of the biggest standouts through the drive, apart from the fact that I wasn’t white-knuckling as much as anticipated thanks to features such as up and downhill assist, was just how smooth the ride was. This, according to GMC, was a result of the Sierra HD being engineered with an independent front suspension that provides better ride shake and ride comfort while trailering.

Safety and Technology Updates

GM's 15-view camera system — which is also found in the 2020 GMC Sierra 1500 and Chevrolet Silverado — was also a big boon during the drive experience. Transparent trailering continues to be a joy to use, as it provides a clear picture of what’s behind you even when towing a large trailer.

All the other camera views are useful and have their place, like providing clear views of your left and right side when signaling a left or right turn, but it never gets old to turn the hulking trailer behind you invisible.

Additional tech that is available on the Sierra 2500/3500 is a segment-first rear camera mirror and an adaptive cruise control camera. The adaptive cruise control camera will be available on the SLT, AT4 and Denali trims. A multi-color head-up display —which projects customizable data such as speed, navigation, etc. on the car windshield — is also available. 

And, it's hard not to notice the truck's six-function tailgate, which offers various solutions and in my experience made getting to certain parts of the box much easier. 

For fleets that are interested, GMC is offering factory installed power take-off Allison 10-speed transmission-equipped Sierra HDs.

2020 GMC Sierra 2500/3500 Diesel Specs: 

• Engine: 6.6L Duramax turbo diesel (445 hp, 910 lb.-ft.)

• Transmission: Allison 10-speed transmission

• Towing: 35,500 lbs.