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GMC’s Sierra HD 2500 Denali – MOUNTING UP

Climbing rocky, muddy, and mountainous roads is just another day at the office for the 2025 GMC Sierra HD 2500 Denali. (Photo by Bill Owney)

Car Reviews

GMC’s Sierra HD 2500 Denali – MOUNTING UP

GMC’s Sierra HD 2500 Denali

MOUNTING UP

DRY CREEK, Ark. – Some fifty miles, as the crow flies, east of the spectacular state park of a similar name, North Petit Jean Mountain towers above the northernmost river valley of the Ouachitas, a Caddoan word for ‘big hunt’, which signified that here was the place to seek the Buffalo who once roamed the linear, east-west river plains separating the mountains.

Dawn broke chilly and overcast over my campsite on Blue Mountain Lake, at the foot of Mount Magazine, and though my phone had zero bars, the flawless Wi-Fi in the 2025 GMC Sierra Denali Diesel 2500 rapidly opened a weather app. A stormy afternoon was in the offing, but I had a plan for the day.

While my water heated, I pulled out tarps and trenching tools and rain-proofed the tent. After filling my canteen with steaming hot coffee, I headed up the mountain for a five-mile hike.

Mount Magazine State Park is chock full of lovely trails. I chose a lesser-known one that runs from Brown’s Spring out along a ridge providing dramatic views of the Arkansas River Valley before circling back for equally spectacular views of Petit Jean Valley, from whence I could see the oncoming storm. 

It was the culmination of a rainy week in the mountains, which meant waterfalls and gushing streams. Sometimes, the trail and streams coincided. The water reflected the light as through etched crystal, creating infinite fractals that reminded us that God created the earth, and he created us from it.

Caked in mud, a 2025 GMC Sierra HD 2500 Denali prepares for another run up North Petit Jean Mountain. (Photo by Bill Owney)

Rocky paths set amid stubby, gnarled cedar lead to the tops of towering cliffs. Songbirds darted in the undergrowth while raptors preyed at the same altitude as the trails. A brilliant hawk whooshed by like a fighter plane, going from unknown to unseen again in milliseconds. I acknowledge his stunning entrance and exit by bidding him a good day, too.

The trail is frequently interrupted by offshoots to the palisades, and I took every one, angling to photograph gurgling, laughing, and dancing waterfalls spilling off the cliffs. More than once, I thought I had captured the perfect angle, only to go just a little further and discover more complexity, beauty, and richness than I first perceived. Lately, I have noticed the same about people, too, and I hope someday to extend the same courtesy to myself.

I was shooting photos from a cliff top when disaster nearly struck. I violated my second cardinal rule — do not drop the darn phone. Fortuitously, I obeyed the first and third: Stay away from the edge and use an industrial-strength case.

Soon, a mixture of sleet and light rain informed me that the storm was approaching. I had rain gear, waterproof hiking boots, and wool socks (they dry fast), so I was okay. I walk-jogged the last mile or so back to the inviting confines of the truck.

I discovered the night before that the GMC’s plush interior, including concert-quality music and heated seats with massagers, made sitting in a warm truck surfing the internet on a winter’s eve even more enjoyable than hanging out in a tent with a large air mattress, electric blanket, and space heater. 

I love camping, but roughing it? At my age? Are you nuts?

It was the week after Christmas, and the weather was inhospitable, so Mount Magazine’s cliff-side lodge was empty. Soon, I was sitting in front of giant windows with a panoramic view of the Petit Jean Valley. 

As the storm whipped across the valley, obscuring the mountains on the other side, I enjoyed a hot meal and fresh coffee while reading Simon Wiesenthal’s The Sunflower. After the leading edge passed, hours of steady rainfall followed.

Not a problem.

I had camped at Blue Mountain Lake before and used it as a base to explore nearby state parks or take day trips further north into the Ozarks, but had never explored the mountains on the valley’s southern edge. My trail apps show nothing in hundreds of square miles, and it turns out that they are accurate. Other than scattered desolate towns and off-the-grid housing in the valleys, this portion of the Ouachita National Forest is desolate. The U.S. Forest Service maintains the only roads, and I use maintain in the sketchiest sense.

With nothing better to do on a rainy afternoon, I figured a heavy-duty truck with four-wheel drive, 18-inch wheels, a beefy suspension, and a 6.6L V-8 turbodiesel with 470 hp and 975 ft-lb of torque bolted to a 10-speed Allison® transmission might be up to the task. As it turns out, despite miles of slick mud punctuated by a dozen fords through raging streams and brutally rocky and uneven tall climbs that would scare off a side-by-side, the truck was overqualified.

Swollen streams pose no challenge for a 2025 GMC Sierra HD 2500 Denali. (Photo by Bill Owney)

I wound up putting on more than 60 miles on uninhabited roads, and the worst thing that happened was the truck got muddy. Less than a mile from a state highway, a washed-out bridge foiled the first route I plotted. Fortunately, Google Maps and Wi-Fi continued to work flawlessly, and I quickly spotted another route out. 

That led to an underwater concrete ford that would have been passable if not for a large, downed tree lying across it. I tried another route up and over a mountain, but when I reached my final turn, I discovered the Forest Service had permanently closed the road by bulldozing a large pile of dirt at the entrance (mental note: go back and hike that thing).

At that point, there was nothing to do but backtrack. Again, I had no bars on the phone, but the Wi-Fi was five-by-five. I put in the campground, and off we went. I was back in my dry tent before sunset with a deep appreciation for a vehicle that made light of traveling to places I would never venture with my Highlander.

A GMC Sierra HD Diesel Denali starts at around $80,000, and dressed-out models like our tester can reach close to $100,000. It might make economic sense when used as a work truck or long-distance hauler. For buyers who want the best, it checks that box. 

It offers a comfortable and well-appointed cabin with ample space for up to six passengers. The interior features durable materials that are easy to clean and maintain. The cabin provides multiple storage options and thoughtful ergonomics.

The 2025 GMC Sierra HD 2500 Denali cabin is plush and filled with digital technology. (GM photo)

The Sierra 2500 Diesel has advanced technology features, including a standard 8-inch touchscreen infotainment system (ours had an optional 12.3-inch display that simplified reading a map on the fly), Apple CarPlay, and Android Auto. Multiple USB ports throughout the cabin kept all my electronics gear fully charged. The Denali trim boasts a 15-inch head-up display and a Bose premium audio system.

Thanks to its robust chassis and advanced suspension system the truck offers a smooth ride. The Sierra HD handles well for its (large!) size, with responsive steering and a well-planted feel. These trucks ride best when under load. Our tester came with the available adaptive suspension, which eliminated truck-like bounciness. 

The four-wheel drive system provides reliable performance in various driving conditions, and the diesel engine delivers strong low-end torque for towing and hauling. I left in four-wheel high automatic off the beaten path, and it did the rest.

The GMC Sierra 2500 Diesel has a good reputation for reliability. The engine is solid, though the 10-speed is getting a reputation as a problem spot. Our tester exhibited sporadic, uneven shifts, but this was a press fleet vehicle, and those tend to suffer abuse (see above). Predicted reliability ratings are above average, and resale values should be strong. The Sierra Diesel has a competitive package, including a 3-year/36,000-mile basic warranty and a 5-year/60,000-mile powertrain warranty.

I have no qualms about recommending any American-made heavy-duty pickup. In addition to its cousin, the Chevrolet Silverado HD, the Sierra HD takes on stalwart competition from Ford and Ram:

  • 2025 Ford F-250 Super Duty: A popular choice in the heavy-duty pickup segment, with a starting price of $49,130. The F-250 offers a range of engine options, including a powerful diesel engine. Towing capacity varies based on configuration. Strengths include its versatility and strong reputation, while some critics note the ride quality is not as smooth as competitors.
  • 2025 Ram 2500: Known for its luxurious interiors and smooth ride, the Ram 2500 offers a diesel option with impressive torque for towing. Pricing ranges from $46,000 to $90,000, depending on configuration. Strengths include a comfortable ride and upscale interior, while the infotainment system may be less user-friendly than competitors.

Frankly, I would take any to the mountains.

In four decades of journalism, Bill Owney has picked up awards for his coverage of everything from murders to the NFL to state and local government. He added the automotive world to his portfolio in the mid '90s.

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