A potent pickup truck now with off-roading capabilities!

When we used to talk about pickup trucks a decade ago, the general notion was a barebone truck that only knows how to lift weights. It was also taken for granted that, since they are tough vehicles, even off-roading would be easy. But, like we all know, a pickup truck is not automatically qualified to explore untraveled or non-existent roads. Fast forward to 2019, and GMC has launched a truck called the GMC Sierra HD AT4 that is muscular, can travel off-road without showing its ’jungli-ness’, and has an interior that can put well-loaded sedans and SUVs to shame. We finally have a heavy duty version of the Sierra AT4, so let’s check it out, shall we?


The 2020 GMC Sierra HD AT4 is for those folks who are looking for a no non-sense truck. It looks mean, aggressive, and has a design language that will grow on you soon enough. The GMC Sierra HD has never stolen the limelight in its lifetime; sometimes because of the competition, sometimes because it plays wingman to its cousin, the Silverado HD. However, GMC has decided to distinguish the Heavy-Duty Sierra in three different forms - the base Sierra HD, the Sierra HD AT4, and the Sierra HD Denali - each one being a more luxurious hero in its own way.


  • A fully-functioning head scoop
  • Black Chrome detailing
  • MultiPro Tailgate
2020 GMC Sierra HD AT4 Exterior
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First things first - the 2020 GMC Sierra HD AT4 is intimidating and scary no matter which angle you look at it. Unlike its counterparts, the Sierra HD AT4 does not receive an overdose of chrome anywhere on its body. The dark theme looks classy and butch at the same time. The hood has a fully-functional hood scoop to cool off the big ol’ engine underneath.

The GMC Sierra HD AT4 comes with the same-sized grille as the Sierra HD, but with different design cue.

It does not receive the gawdy chrome treatment and has rather proportionate, slim horizontal slats in the front and vertical in the rear. The headlights are the same, large-sized units found on the Sierra HD that feature C-shaped LEDs and daytime running lights. The bumper is finished in body color and houses the foglamp units as well. The bottom of the bumper receives black plastic cladding that is more prominent than that of the Sierra HD. The tow hooks are painted in red which make them more prominent when compared to the hooks on the Sierra HD.

The side profile looks neat with a large-sized wing mirror and a badge each on the front fender and the side door. The 18-inch wheels wrapped in Michelin tires look a tad bit small, thanks to a raised stance and flared wheel arches. There is an option to upgrade to 20-inch wheels, though, so that’s easily remedied if you have a few extra grand stashed away somewhere. Like its HD counterpart, the 2020 Sierra HD AT4 also comes with a longer wheelbase than the 2019 model.

Generally, automakers do not pay attention to the tailgate of a truck. In a majority of the cases, the rear looks too plain when compared the garish front. GMC, however, has managed to make the rear look uncommon without meddling around much.

The chiselled rear on the 2020 GMC Sierra HD AT4 looks very smart. Extra brownie points to the automaker for that.

The derrière looks exactly the same as the Sierra HD except for the dual tip exhaust with silver finish. The six-way adjustable MultiPro tailgate makes its way here. It is one of the most innovative tailgates that offers six unique functions and positions to help work or load things into the bed much easier than with a standard tailgale. The MultiPro tailgate can support up to 375 pounds and has two buttons for operation and inner gate release.

GMC Sierra HD Exterior Dimensions

Double Cab Crew Cab
Wheelbase (in. / mm): 144.2 / 3662 – 6’6” box
158.1 / 4017 – 8’ box
153.7 / 3904 – 6’6” box
167.7 / 4258 – 8’ box
Overall Length (in. / mm): 230 / 5842 – 6’6” box
248.9 / 6322 – 8’ box
239.5 / 6083 – 6’6” box
258.4 / 6563 – 8’ box
Overall Width (in. / mm): 80.5 / 2045 80.5 / 2045
Overall Height (in. / mm): 78 / 1983 (4WD w/ 6’6” box)
77.9 / 1978 (2WD w/ 8’ box)
77.8 / 1977 (4WD w/ 8’ box)
78.2 / 1988 (2WD w/ 6’6” box)
78.2 / 1987 (4WD w/ 6’6” box)
78 / 1981 (2WD w/ 8’ box)
77.9 / 1980 (4WD w/ 8’ box)

Note: 2019 GMC Sierra HD exterior dimensions listed here.


  • 4-camera setup for easy maneuvering
  • Compatible CarbonPro Fiber Box
  • Multiple storage spaces at the rear
2020 GMC Sierra HD AT4
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The 2020 GMC Sierra HD AT4 calls itself a premium truck with the best of technologies. The dark theme continues on the inside of the truck as well.

The interior sports a unique darkened trim that includes center stack and sill plates, jet black accents, and leather upholstery with AT4 badging on the seat headrests.

The steering wheel comes with a textured aluminum finish which makes it a delight to hold. Move to rear and you will realise how utilitarian the cabin actually is. The rear seatback opens all the way to reveal a pair of 10-liter rectangular storage spaces that can hold tablets, ropes and cords, apart from other personal items. The is a large 24-liter storage beneath the second-row as well.

Other features that add to the oomph factor include:

  • A 15-inch diagonal Head-Up Display with Off-Road Inclinometer,
  • An infotainment system that supports both, Android Auto and Apple CarPlay.
  • As opposed to the GMC Sierra HD’s 15-camera setup, the Sierra HD AT4 comes with HD Surround Vision1 - a set of four cameras installed on either side of the truck
  • for low-speed views of the Sierra HD AT4’s surroundings. This is very helpful when parking in tight spots and navigating through congested paths.
  • The clever Rear Camera Mirror technology that was seen in the Cadillac also finds its way here.

The 2019 Sierra AT4 came with a fiber composite box that GMC calls the CarbonPro box. The automaker claims CarbonPro box is the first-of-its-kind in the industry and is developed to increase durability, efficiency, and functionality of the truck. The CarbonPro box replaces the standard steel inner panels and floor with a lightweight, purpose-designed carbon fiber composite material that is resistant to scratches and corrosion. In fact, this box was designed with the AT4 model in mind as it helps lug cargo easily and safely through unknown territories.

GMC Sierra HD interior dimensions

Double Cab Crew Cab
Headroom (in. / mm): 42.8 / 1087 (front)
38.7 / 982 (rear)
42.8 / 1087 (front)
40.5 / 1029 (rear)
Legroom (in. / mm): 45.3 / 1150 (front)
34.6 / 880 (rear)
45.3 / 1150 (front)
40.9 / 1040 (rear)
Shoulder room (in. / mm): 64.8 / 1647 (front)
64.3 / 1634 (rear)
64.8 / 1647 (front)
64.3 / 1634 (rear)
Hip room (in. / mm): 60.7 / 1543 (front)
60.2 / 1530 (rear)
60.7 / 1543 (front)
60.2 / 1530 (rear)

Note: 2019 GMC Sierra HD interior dimensions listed here.


  • 6.6-liter diesel engine
  • 455 horsepower
  • 910 pound-feet of torque
  • 6.6-liter gas engine available
  • 10-speed automatic standard
  • 8-speed auto with gasoline engine
  • Rancho shocks
  • 30,000+lb towing capacity
  • Eaton locking rear differential
2020 GMC Sierra HD AT4 Exterior
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When you own a truck like the Sierra HD AT4, you just cannot make do with a puny engine.

GMC has instilled the 2020 Sierra HD AT4's engine bay with a 6.6-liter, V-8 Duramax diesel engine that produces 445 horses and 910 pound-feet of torque.

This is slightly less than the new Ram HD’s 1,000 pound-feet of torque, but not enough to keep it from being on par with the competition. You will obviously not go off-roading with a trailer on your ass; so the 910 pound-feet torque is adequate when you are off-roading. The engine will be mated to 10-speed automatic transmission. A 6.6-liter, V-8 gasoline engine will replace the 2019 model’s 6.0-liter, V-8 L96 unit. The new mill will produce 400 ponies and 450 pound-feet of torque, and will be mated to a new GM 8-speed Allison heavy duty automatic transmission.

The USP of the 2020 GMC Sierra HD AT4 is its off-roading prowess.

GMC has used a unique off-road suspension setup and host of other equipment like the Rancho Shocks, skid plates, and Eaton locking rear differential.

You can even choose Traction Select System, which is basically allows you switch drive modes to make real-time adjustments based on the driving situation, with the off-Road mode as well. To make things easier, GMC has also provided Hill Descent Control, Hill Start Assist, Auto Electric Park Brake, and Park Grade Hold Assist in the Sierra HD AT4. The company has not announced the exact towing ratings, yet but expect it to pull more than 30,000 pounds. The 2019 GMC Sierra AT4 could tow 9,400 pounds. The 2019 GMC Sierra HD, on the other hand, could tow 23,300 pounds, so it’ll be a big improvement in that department either way.

2020 GMC Sierra HD AT4 drivetrain specifications

Engine 6.6-liter diesel 6.6-liter, V-8
Horsepower 455 horsepower 400 horse power
Torque 910 pound-feet 450 pound-feet
Transmission 10-speed automatic 8-speed Allison heavy duty automatic


Ford F-150 Raptor

2017 Ford F-150 Raptor
- image 661370

The Ford F-150 Raptor is the go-to choice for any prospective buyer of this category. As in the norm, the F-150 Raptor also comes with a huge grille upfront, but it adds so much to the character of the truck. The huge FORD lettering has been slapped on the grille and this make the truck absolutely drool-worthy. Unlike the Sierra HD AT4’s square-ish wheel arches, the F-150 Raptor comes with beautiful, flared, and beefed-up wheel arches that only make the truck desirable. On the inside, the Raptor feels nice and comfortable, but it is not a posh cabin whatsoever. The creature comforts are aplenty to keep you engaged, like a touchscreen infotainment system that supports Apple CarPlay and Android Auto, paddle shifters, etc. But if you need the plush feel, you need to go for optional packages; as is the case with any other Ford.

Under the hood, the Ford F-150 Raptor has the winning formula. The truck is powered by a 3.5-liter, EcoBoost, V-6 that produces 450 horsepower and 510 pound-feet of torque. This is much smaller than the 6.2-liter V-8 engine it replaces but is significantly more powerful and is mated to a new 10-speed automatic transmission. The torque figures are very low compared to the Sierra HD AT4, but don’t let that fool you. The F-150 Raptor comes equipped with a torque-on-demand unit that provides the perfect power distribution between the front and rear axles. Then there is the Terrain Management System that gives access to six modes, including Normal, Street, Weather, Mud and Sand, Rock, and Baja. So, these supporting technologies do their job well to eclipse the deficit torque.

Read our full review on the 2018 Ford F-150 Raptor

Ram HD

2019 Ram Heavy Duty Looks Menacing, Pumps out 1,000 Pound-Feet! Exterior
- image 814536

The Ram HD is a truck that makes the Sierra HD AT4’s mouth look small. The Ram HD literally transformed itself from a beast to a monster, growing in all aspects with the latest model. Under the hood of the Ram HD is a 6.7-liter Cummins turbodiesel engine that produces a mammoth 1,000 pound-feet of torque but a mere 400 horses. The higher torque could have made up for it to a certain extent, but the Ram HD comes mated to a six-speed automatic transmission, thus limiting its potential to a certain extent. The same unit is available with a lower power output rating as well, with just 370 ponies and 850 pound-feet of torque. The base trim is powered by a 6.4-liter Hemi V-8 engine that produces 410 horsepower and 429 pound-feet of torque. The automaker has reworked its chassis and body, which enabled it to shave off 143 pounds of the curb weight when compared to the previous model.

On the inside, it may not seem as lush as the GMC Sierra, but Ram has offered all the creature comforts. The console area is now 22.6 liters, 2.9 liters larger than the 2019 model, and includes 12 storage configurations. You can hold bigger items like tablets in it now. The base trim comes with a 5-inch infotainment system, while the higher trims can be availed with 8.4-inch or 12-inch screens. It also comes with five USB ports, three 115-volt plugs, and wireless charging docks. As of now, the Ram HD isn’t offered in an off-road guise, so you’ll have to tough it out without all of the extra off-road goodies you’ll find on the F-150 Raptor or Sierra HD AT4

Read our full review on the 2019 Ram 2500 Power Wagon.

Final Thoughts

2020 GMC Sierra HD AT4 Exterior
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The 2020 GMC Sierra HD AT4 seems like a better overall package when compared to the light-duty, 2019 Sierra AT4. The new 10-speed Allison transmission covers up for the fact that GMC missed the opportunity to hit the four-figure torque mark. It can make driving with heavy loads a little more sprightly and peppy. Features like the 15-inch head-up display, the 4-camera setup, the Traction Select System, the off-road equipment, and a multi-mode tailgate make things a lot more interesting in day-to-day use. The 2020 GMC Sierra HD AT4 will be built at the company’s Flint Assembly in Flint, Michigan and, although the launch date is not set in stone, we expect it to arrive in showrooms in Summer 2019 along with the 2020 GMC Sierra HD. Based on history, the GMC Sierra HD has sold 50-percent of its trucks in the Denali trim.

  • Leave it
    • Will not please everyone in the looks department; the 2019 Sierra AT4 looked much smarter.
    • Misses out on features like the 15-camera setup from the Sierra HD.
    • Since the Sierra HD is a better all-rounded package this time and more than half the Sierra trims sold are Denali, the AT4 may not be a popular choice.

Further Reading

2020 GMC Sierra HD Exterior
- image 817271

Read our full review on the 2020 GMC Sierra HD.

2019 GMC Sierra Exterior
- image 771288
The 6.2 and 5.3-liter were updated

Read our full review on the 2019 GMC Sierra.

All-new Sierra AT4 HD: Refined HD Capability Off-Road
The all-new 2020 Sierra Heavy Duty AT4 continues the AT4 brand’s growth with a distinctive off-road identity to complement its robust HD capability. Driven by dark chrome exterior finishes and contemporary detailing, Sierra HD AT4 features front and rear bumpers and a grille surround finished in body color. The bold grille design, with its rugged texture, is finished in black chrome and set off by the AT4’s distinctive red vertical recovery hooks. The athletic interior also carries AT4-specific darkened trim, including dark-tinted and textured aluminum finishes on the steering wheel, center stack and sill plates, as well as a unique Jet Black interior with Kalahari color accents in the seats and live stitching. Leather-appointed seating, with mini-perforated inserts and embroidered AT4 badging on the headrests, along with all-weather floor liners, is standard delivering durability with uncompromising comfort. The new Sierra AT4 Heavy Duty’s off-road capabilities are rooted in a unique suspension and supporting technologies that include: Off-road suspension, Rancho Shocks, skid plates, Eaton locking rear differential.
Eighteen-inch wheels wrapped with Michelin all-terrain tires, with 20-inch wheels available.
Traction Select System with specific Off-Road mode.
Hill Descent Control and Hill Start Assist.
Segment-exclusive 15-inch diagonal Head-Up Display with Off-Road Inclinometer.
HD Surround Vision1 for low-speed views of vehicle surroundings.
Confident trailering power
GMC’s legendary Duramax turbo diesel and Allison Transmission pairing continues to offer the ultimate in towing confidence. The proven Duramax 6.6L turbo-diesel engine offers high torque, high power, low noise and exceptional durability. For the 2020 Sierra HD, the Duramax offers an SAE-certified 445 horsepower and 910 lb-ft of torque. This already powerful engine performs more efficiently thanks to increased cooling capacity delivered in part by improved air induction. A dual-path intake system draws dense, cool air through both the prominent hood scoop and the larger front grille.

Press release
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