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GM confirms 2015 Silverado, Sierra to get 8-speed automatic

When viewed alongside the next Ford F-150 and the Ram 1500, there is one thing that seems to be missing from the Chevrolet Silverado and GMC Sierra. Where the F-150 will rely on turbocharging and aluminum architecture and the Ram sports an eight-speed automatic and an air suspension, the General Motors twins lack a big, calling-card feature. They're very good, very refined trucks, but one could argue that they're not terribly innovative.
And while it might not be as flashy a feature as air suspension or a lightweight skin, the Silverado and Sierra will get their own eight-speed automatic for 2015, a transmission that will be paired with the company's Ecotec3 6.2-liter V8. The new cogswapper will also find its way into the GMC Yukon Denali, but for now, there's no indication why the Cadillac Escalade, Suburban, Tahoe and standard Yukon are being left out.
According to GM, the new gearbox is about the same size and weight as the current Hydra-Matic 6L80 six-speed. By the time the new powertrain combination enters production late this year, the EPA will almost certainly have gotten around to certifying the vehicles' fuel efficiency. Until then, feel free to speculate. The current Silverado with the 6.2 and six-speed auto returns 14 miles per gallon in the city and 20 on the highway. How much do you think the eight-speed will improve those figures? Scroll down for the official press blast from General Motors, and then head into Comments.

Supercharged 2015 GMC Yukon Denali sounds evil, runs 0-60 in 4.5 seconds

Speeding along in a sports car is undoubtedly a ton of fun, but some owners need the ability to carry a lot of people and their stuff and don't want to sacrifice the ability to put the power down. The tuners over at Hennessey have that demographic covered with their growling, supercharged power kits for the GMC Yukon Denali. The upgrades come in three forms for the SUV's 6.2-liter V8: HPE550 with 557 horsepower, HPE600 with 605 hp and HPE650 with 665 hp. This video showcases the full-bore version, and this Denali can definitely hustle in a straight line. The power bump comes courtesy of a 2.9-liter supercharger, intercooler and high-flow cylinder heads to add over 200 horsepower compared to stock, and the final result is a bellowing SUV that rears up off he line to throw the driver back into the seat. The sprint to 60 miles per hour lasts just 4.5 seconds. Check out this hasty hauler in action in the video above.

GM's fullsize SUVs boost highway mileage by nearly 10 percent

We met the redesigned 2015 versions of the Chevrolet Suburban and Tahoe, and the GMC Yukon and Yukon XL at the 2013 LA Auto Show. Improved gas mileage numbers have been announced to go along with the improved exteriors and interiors, with city mileage improving by seven percent and highway mileage going up by nearly ten percent; you'll now get 16 miles per gallon in the city and 23 on the highway.
The only applies to models with the 5.3-liter engine, though, not the premium Yukon Denali and Yukon XL Denali SUVs with the 6.2-liter motor. Still, the 5.3 gets you more power than previously, with 355 horsepower and 383 pound-feet of torque underfoot, on top of the improved fuel economy numbers. The 6.2-liter sticks with official mpg ratings of 15 highway, 21 city. There's a brief press release below with words straight from the horse's mouth.