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2019 GMC Sierra AT4 First Drive Review | Off-road overkill

The road ahead is dirt with a rut here and a rock there. Brush keeps a respectable distance on the right side, the edge on the left gradually falls away into the valley below. The grade is nothing your treadmill couldn't duplicate and traction is pretty good. Honestly, a couple in their Subaru Crosstrek could pop up here for a picnic. The 2019 GMC Sierra AT4 we're driving is therefore complete overkill. But at least it looks the part as it trudges up this uncharacteristically verdant mountain with San Diego in the distance to the north and Mexico to the south. Its special, dechromed AT4 grille has a purposeful appearance, but tastefully lacks the show-off machismo of Ford and Ram's off-roading models. The red tow hooks are a nice touch and the dark-accented 20-inch wheels wrapped in all-terrain rubber are just the right size beneath a suspension that is raised an extra 2 inches from every other Sierra. That would be one of the key elements that differentiates the AT4 as the Sierra's off-roading model – GMC's answer to the Chevy Silverado's Trail Boss trims. In fact, their mechanical enhancements are identical. Besides the 2-inch lift, the suspension features off-road-tuned Rancho monotube shocks. There's also a locking rear differential, a two-speed transfer case, skid plates and those tow hooks. The 5.3-liter V8 with Dynamic Fuel Management is similarly standard, but unlike the Silverado Trail Boss, the Sierra AT4 offers the 6.2-liter V8 good for 420 horsepower and 460 pound-feet of torque as a roughly $2,500 option. That's the engine we have and it delivers the expected punch, complete with a satisfyingly snarling exhaust note. However, as observed in back-to-back drives with these two available engines during the Silverado launch, the 6.2 certainly isn't necessary. The 5.3-liter is seriously capable and the bigger engine is largely for those who want to have the biggest number possible emblazoned on the fender. It's overkill, which in this particular environment, is fitting. Besides the available engine upgrade, the AT4 also goes beyond its Trail Boss counterpart by dipping into the Sierra Denali's tool box. Its MultiPro tailgate is standard equipment, allowing for six different configurations, the most notable of which include a means of more easily reaching into the bed and a drop-down step that eases entry into the bed. GMC's considerable touting of that last element is rife with hypocrisy given GM advertisements that mocked Ford's similar feature.

GMC Sierra Denali CarbonPro bed is finally, almost here

GMC revealed the Sierra 1500 with the optional CarbonPro bed on March 1, 2018. The bed wasn't available at launch, though. You can't buy it now, either, but it will hit dealerships with limited availability after production starts in early June, exclusively for the Denali 1500 and AT4 1500 trims. The carbon floor and sides replace the steel panels in a normal bed, providing "strength, durability, and scratch resistance" and a potential 59-pound weight saving, depending on the truck's configuration. To make sure the bed had a chance, development engineers replicated "extreme use scenarios" like dropping 1,800-pound gravel loads, 450-pound steel drums, and cinder blocks from various heights. They put a 250-pound man on a snowmobile with studded tracks, had him drive into the bed and then go wide-open throttle. We're told the result was "minimal scratching." On top of the extreme weather testing any vehicle goes through, the team also put a generator in the bed and aim the exhaust into a corner to ensure vibration and direct heat wouldn't deform the carbon fiber. Because of the finer shaping area-specific strength possible with carbon fiber, the bed provides one cubic foot of additional payload space by having its sidewalls pushed further out. The CarbonPro bed doesn't need a bedliner, and is grained at the top for better traction but smooth on the bottom for easier hosing down and dirt removal. Tie-downs at the front of the bed work with molded indentations to hold motorcycle tires, and slots in the sidewalls hold two-by-sixes. The truck maker says the carbon-lined payload area confers "best-in-class dent, scratch and corrosion resistance," but we suppose the nation's pickup truck army will prove that or not. The trucks likely won't have the hardest life at the start, since the Sierra Denali costs $56,790 before even a basic option like four-wheel drive. The real test probably won't come until around 2029, when third owners begin treating their aerospace-inspired thoroughbreds like dray horses.

GM exploring ways to raise half-ton Duramax diesel tow rating

Lots of truck owners cheered when GM announced fuel economy numbers for the 2020 Chevrolet Silverado with the 3.0-liter Duramax diesel inline-six. Even after Ram let loose its EPA mileage ratings for the 2020 Ram 1500 EcoDiesel, the Chevy oil-burner still took the trophy. The victory was years in the making, GM engineers spending an entire four-year development cycle refining the LM2 Duramax to increase mileage. The tradeoff, as well all know by now, is towing; the Duramax in half-ton duty pulls a maximum 9,300 pounds in the Silverado. Rivals across town can do more, the Ford F-150 PowerStroke rated at 11,500, the Ram 1500 EcoDiesel game to pull 12,560. GM engineer John Barta told Muscle Cars & Trucks that more hauling chops could be on the way, explaining, "We’re actually looking at upgrading some of the materials around (the engine bay) to see if we can maybe raise our tow rating." Engine bay materials are at issue due to thermal complexities underhood. John Barta, GM's assistant chief engineer of diesel engine controls, said the Duramax's inline-six configuration allowed engineers to get emissions hardware like the combined selective catalytic reduction, diesel oxidation catalysts, and diesel particulate filter unit closer to the engine, where it heats up quicker, getting emissions down quicker. But that filter puts another heat source in those confines, enforcing a cap on the tow rating to keep the engine and other systems from overheating. "If you look under the hood," he said, "youÂ’ll see a significant amount of silver ‘moon tapeÂ’ around to make sure things arenÂ’t getting overheatedÂ… if we were to go up in higher towing, which we can, we start impacting the possibility of deteriorating some of the components.” There isn't much space for more grille, so swapping for a better grade of "moon tape" or a different kind of material could reduce engine bay heat, extracting a higher tow rating in the process.  It's important to note a point Barta's been making for months about the Duramax figures, though. "Even though itÂ’s nice to brag about big numbers, in reality, light duty customers are not towing that large with their trucks," and, "We do know that (95 percent) of our light duty customers donÂ’t tow over 9,000 pounds." On our First Drive of the 2020 Silverado diesel we called out the tow rating, but emphasized that the Chevy and GMC have more important challenges to overcome.