GM is not being subtle about the new Sierra. The company has been feeding details to media in waves since August. The latest look at the 2027 GMC Sierra 1500 Denali Ultimate and AT4X reveals two trucks chasing very different buyers with the same basic bones.
Start with the number that matters most: 900 miles. That is GM’s claimed range from the returning light-duty Duramax diesel paired with a new 34-gallon fuel tank. Back-of-the-envelope math puts that at roughly 26 mpg, which is genuinely impressive for a full-size pickup.
The diesel option had disappeared from the light-duty Sierra lineup. Its return signals GM sees a real market for buyers who want to tow without stopping every 400 miles.
The Denali Ultimate is unambiguously the six-figure flagship. Its low front air dam and automatic running boards telegraph a truck that wants pavement, not Moab. Inside, GMC leaned into what it calls topographical relief detailing, embossing contour-map patterns into the leather door cards and seat upholstery.
Real wood, brushed metal, and enough screen acreage to land a small aircraft round out the cabin.
But the screens are the real story here. GMC split the digital real estate into four zones: instrument cluster, center display, head-up display, and a dedicated passenger screen. The saving grace is that GMC kept physical controls for core functions like audio volume and the trailer brake controller.
That alone puts it ahead of competitors who buried everything in touchscreen menus and called it progress.
One detail stands out. The center screen folds back to reveal a hidden storage cubby. It is small, wallet-sized, but in a truck where theft from the cab is a real concern, it is a smart touch.
The passenger screen partially stows when not in use, which prevents it from becoming a permanent distraction.
The AT4X takes the opposite approach to nearly everything. The air dam is gone. Running boards are gone. Ground clearance goes up.
The wheels shrink while the tires, 35-inch Goodyear Wrangler Territory MTs, grow substantially. GMC even repositioned the front tow hooks from vertical to horizontal to squeeze out a better approach angle. That is the kind of functional detail that separates a real off-road truck from one wearing a costume.
Inside, the AT4X dials back the luxury without stripping it entirely. You still get the panoramic roof, headrest speakers, and all that screen real estate with the same physical controls. The materials just trade polished surfaces for something more utilitarian.
Underneath both trucks sits GM’s new family of small-block V8 engines, though GMC has been stingy with specifics. The architecture is entirely new, which is no small undertaking for a company that has leaned on iterations of its small-block platform for decades.
What GM is really doing is widening the gap between its two halo trims. The Denali Ultimate and AT4X used to feel like variations on a theme. Now they feel like different trucks aimed at buyers who might never cross-shop each other.
The diesel-range highway cruiser and the mud-ready rock crawler share a badge, but not much of a mission. GM says more details on the full 2027 lineup are coming. Given how carefully the company has been rationing information, expect this drip feed to continue well into next year.
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