2007 GMC Sierra By Larry Edsall, New Car Test Drive .com

GMC is the best-kept secret at General Motors. With the exception of Chevrolet, GMC is GM's best-selling division. And that's without a single passenger car in its lineup. GMC sells more trucks and sport utility vehicles than Pontiac, Cadillac, Buick, Saturn, Saab or Hummer sells of anything.

But GMC may have trouble keeping itself secret after the launch of its all-new 2007 Sierra full-size pickups. Not only will these trucks be more aerodynamic and fuel efficient, offering better than 20 miles per gallon on the highway, but there will be an all-new Sierra Denali version that could become a breakthrough in the lux-truck category.

In addition to being packed with all sorts of luxury interior accoutrements, the GMC Sierra Denali will be powered exclusively by a 6.2-liter V8 engine with variable valve timing that will not only hit the 400-horsepower mark but will offer 417 pound-feet of torque. It'll come with a new six-speed automatic and a choice of two-wheel drive or all-wheel drive.

The Denali will be the top of a lineup that includes WT, SLE and SLT versions. Buyers will be able to select between two different interiors: "pure" pickup and "luxury-inspired." Three cab styles, three bed lengths, five suspension packages and eight powertrain combinations are available.

The all-new 2007 GMC Sierra is expected to go on sale October 2006.

Visually, the Sierra will be differentiated from the Chevy Silverado. The new Sierra borrows GMC Yukon styling cues, with stacked, rectangular headlamps, a full chrome bumper and a subtle power dome hood.

The Sierra was designed both for visual appeal and for improved aerodynamics, which help boost fuel economy. The windshield is raked to 59 degrees and the doors wrap over the rocker panels. GMC says improved aerodynamics and the use of active fuel management allows its 5.3-liter V8 engine to achieve more than 20 mpg on the highway.

Engine choices include a 195-hp 4.3-liter V6, a 295-hp 4.8-liter V8, the 315-hp 5.3-liter V8, a flexible-fuel version of the 5.3-liter V8 that can run on E85 ethanol, a 367-hp 6.0-liter V8, and the Denali's 400-hp 6.2-liter V8. Diesel engines will be available on heavy-duty Sierras, which are scheduled to be in dealerships around February 2007.

Five suspension packages are available: the "solid, smooth ride" Z83, Z85 for enhanced handling and towing, Z71 for off road, Z60 for "maximum street performance" (with 20-inch wheels), and NHT for towing large and heavy trailers.

GMC says the new Sierra, when properly equipped, will tow more than five tons, and can carry as much as 2100 pounds. Speaking of cargo, a cargo-management system with various rails and tracks for securing cargo will be available. Extended cab trucks will have rear access doors that will open to 170 degrees and will have rear windows that power down.

StabiliTrak electronic stability control will be included as standard equipment on crew cab models and will be available on extended cab models. Another safety feature, roof-mounted side-curtain airbags, are on an options list that includes rear park assist, an automatic locking rear axle, remote vehicle starting, DVD/entertainment system, and touch-screen navigation.