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GMC introduces off-road performance package for Sierra AT4

GMC is giving its off-road-focused Sierra AT4 pickup even more performance with some factory-installed upgrades. The package is called the AT4 Off-Road Performance Package. With it you'll get the 6.2-liter V8 engine upgrade, cat-back performance exhaust system, performance air intake and 18-inch aluminum wheels shod in Goodyear Wrangler DuraTrac tires. The upgraded performance comes in the form of extra power. Thanks to the bolt-ons, you gain 15 horsepower and 9 pound-feet of torque over the 6.2-liter in stock form. This increases output to 435 horsepower and 469 pound-feet of torque — not too shabby. This package is priced at $4,940, and available for order now. That's a hefty price for what amounts to some minimal bolt-on modifications you could easily do yourself. However, buying it through GM means you get to keep your warranty in place. The Sierra AT4 already has more off-road features than a normal Sierra 1500. You're getting a two-inch lift, four-wheel drive with two-speed transfer case, locking rear differentials, skid plates, Rancho off-road shocks and hill descent control. Both the wheels and tires are available as options already, but this package just bunches related stuff together. It'll be up to you to decide if an exhaust and intake are worth the extra dough. Related video: This content is hosted by a third party. To view it, please update your privacy preferences. Manage Settings.

Fullsize GM SUVs have a problem that's making owners sick

Some fullsize SUV owners are getting sick, thanks to a buffeting and vibration problem in 2015 model year examples of the Chevy Tahoe and Suburban, Cadillac Escalade, and GMC Yukon. According to owners' complaints to the National Highway Traffic Safety Administration, the issue can vary from an annoying vibration inside the cabin to an experience so severe that it leads to dizziness and headaches. General Motors is aware of the complaints, but the fix isn't so simple. According to spokesperson Tom Wilkinson to Autoblog, the company "has been tracking this issue for a while." The problem has a fairly low incidence rate, but when it does occur the issue can be "uncomfortable and annoying for owners." There's no precise cause for the issue, Wilkinson claims, and in some cases, simply balancing the tires or changing the door seals can make it go away. However, not all of the fixes are so simple. AutoGuide dug deep into the problem and discovered a GM preliminary information bulletin that advised dealers to remove the headliner and to check the roof's bonds to the bows that go across the vehicle. However, that document included a note that the solution might not entirely eliminate things. According to AutoGuide, adding Dynamat insulation to the roof sometimes helped the problem. A GM spokesperson also told AutoGuide the company fixed the problem at the end of the 2015 model year, and didn't go into any more detail. This roof issue seems linked to some of the worst droning in these SUVs. According to one complaint from a 2015 Suburban owner to NHTSA: "Roof will not remain attached to the roof bows. This causes the buffeting similar to a window being down when all are up. The results span from annoying to painful." A 2015 Yukon owner claims to have another alleged cause for the problem in a NHTSA complaint from February 2015. This person brought their SUV to the dealer seven times over the course of four weeks for vibrations. The dealer replaced the driveshaft, suspension components, and more, but nothing worked. According to an engineer to the service adviser: "In an effort to prevent roll overs, they designed the frame and body mounts too stiff. There are 40 engineers working on issues, they have no solutions that work across the board." Wilkinson told Autoblog that GM is working with customers on an individual basis to rectify things. Since these are newer vehicles, dealers should also fix the problem under warranty.

Leaked GM document shows GMC Sierra I6 diesel is more powerful than F-150's

GM told us earlier this year that the 2019 GMC Sierra would be getting a 3.0-liter I6 diesel option, but it never mentioned power or fuel economy figures. Hold the phone though, because a leaked GM Canada document just showed up online that lists out the details we've been waiting for. Originally published by TFL Truck, the 3.0-liter oil-burner supposedly makes 282 horsepower and 450 pound-feet of torque. For those who are counting, that's more than the Ford F-150's 250 horsepower and 440 pound-feet from its 3.0-liter diesel. It soundly bests the 240 horsepower and 420 pound-feet of torque from Ram's 3.0-liter diesel as well. Fuel economy is another story, though. The promotional material states that it will get 28 mpg on the highway, which is 2 mpg short of the F-150's 30 mpg — mind you, it's only capable of that magical 30 mpg figure in rear-wheel drive form. There's another caveat here, too; these are numbers for Canada, so they're not exactly finalized EPA figures. However, we wouldn't expect drastic differences between the two when the American numbers come out. The leaked documents also state the diesel Sierra will be capable of towing 7,800 pounds. That number seems remarkably low when compared to the F-150, which can tow up to 11,400 pounds with its diesel. Extra power and torque would have us assume that GM could get even better numbers than Ford, so we're going to hold our final judgment for official word. A 10-speed automatic will do the shifting on the diesel, just like on the 6.2-liter V8. Since the Chevy Silverado is also expected to get this engine, we can assume the figures would be almost, if not identical, to those we see here. We recently drove the 2019 Sierra and Silverado without the diesel engines, so go check those reviews out if you'd like to know more of our thoughts on the redesigned GM trucks. Related video: