It seems like ages since the Silverado and Sierra -- the GMT900 models -- replaced the GMT800, but it's only been 7 years, at least by the time the new trucks go on sale. While General Motors hasn't revealed the alphanumeric code of this new generation of half-ton truck platform, from what we hear, it will not be called the GMT1000 or something similar. And while the styling of the new Silverado and Sierra are similar to that of the previous 2007-2013 generation, a lot has changed.

As you can see, there is more visual differentiation between the Silverado and Sierra. Each truck has a unique front and rear end. The Silverado's nose uses elements from classic Chevy pickups, such as the four stacked headlights. Much less retro are the available projector-beam headlamps. The new two-section grille has a traditional Chevy look that aligns the front-end styling with that of the current Silverado HD. The Sierra's aggressive nose is much like that of the cool Sierra HD All-Terrain concept from a few years ago. Both trucks have new hoods, and the Silverado's uses twin power domes. In both cases, the manufacturer sealed the front nose, bringing in enough air for cooling while retaining aerodynamics. Also new for the duo are inlaid doors -- previous generations of the Silverado and Sierra had doors that wrapped over the roof. The new doors reduce turbulence to improve aerodynamics, and are triple-sealed to create what GM claims will be best-in-class wind noise reduction. There are more muscular lines along the body, and the fender flares are more prominent.

New for extended cabs are front-hinged rear doors that open without you having to open the front doors first, and crew cabs now have longer rear doors (and shorter front doors), a decision that added 4 inches of space where your feet can swing behind the B-pillars. That makes it easier to get into and out of the rear seats. Legroom has increased by 2 inches.

The cabins, which have been dinged in the past for looking outdated, have taken a huge leap forward. The goal was to make the interiors roomier, more comfortable and functional, and quieter. They're all-new, with new materials, and the cabins in the GMCs look different from those in the Chevys. The six-gauge instrument cluster comes with a 4.2-inch driver information center in most models. There is more storage -- more spaces to carry gear -- and larger door pockets, center console, and two-piece glove box. Other features include an optional 8-inch screen, MyLink/IntelliLink, and standard 110-volt port and multiple USB ports. Unlike in the F-150 and Ram 1500, the trailer brake controller is to the left of the steering wheel. All Silverados and Sierras use a column shifter with tap-up/down shifting and tow/haul located on the shifter.

The biggest news with the new trucks is in the engine bay. Three engines are available in both trucks: a 4.3-liter V-6, a 5.3-liter V-8, and a 6.2-liter V-8. Yes, the displacement numbers are the same, but all three have changed in significant ways. These all-aluminum units are what GM calls EcoTec3 engines, and all use cylinder deactivation, direct injection, and continuously variable valve timing to improve efficiency, and in the case of the last two features, improve performance.

We have grown familiar with cylinder deactivation with the V-8s before, which puts those engines into V-4 mode, but there are changes here, too. This system will also put the V-6 into V-4 mode when in light-load driving conditions. For cylinder deactivation to work, the PCM controls oil pressure to deactivate specific cylinders' lifters, which the company says takes fewer than 20 milliseconds. Not only does that mean the transitions from eight to four cylinders powering the truck are smoother, but the amount of time the engine is in each mode is now said to be more accurate based on the demands put on the truck.

A key element of this trio of engines is the focus on improving combustion efficiency. The engines' combustion chambers, each designed to match the needs of each new engine, are created to control combustion with more precision than in the past. Both the cylinder heads and pistons have been redesigned to improve the way air and fuel mix within the engine; also aiding combustion are the new locations of the intake and exhaust valves. Even the angle of the spark plugs has been changed to put the electrodes closer to the center of the chamber. The V-8's combustion chambers are similar to those of the Corvette. The new design means that the engines can run with a higher compression ratio (11.0:1 for the engines that'll run on regular unleaded).

The company also says that, despite the similarity in displacement to the engines that power the outgoing GMT900-based trucks, only a few components are shared. Some examples of what GM's engineers have worked on: The exhaust manifolds have been redesigned to improve engine durability while reducing noise. The cooling system was made more efficient. There is now oil-jet piston cooling that works when there is higher load demand on the engine. GM has also gone to great lengths to reduce friction within the engines.

As of press time, GM hadn't released horsepower, torque, or fuel-economy numbers, but the company is confident all of them will be significant improvements over the previous generation. GM expects that the V-6 will have best-in-class fuel economy (of normally aspirated V-6s), and unlike the previous 4.3-liter, which was more price leader than an engine that was truly in demand, the V-6 is said to provide enough torque, as GM explains, "to power a crew cab and pull a substantial trailer." Because of that, it'll now be available with every cab and bed combination, and on 4x4 models. And the four-speed automatic is gone -- all three will be backed by six-speed automatics. There should be more horsepower and torque in the 5.3-liter, and the 6.2-liter is anticipated to be not only the engine best suited for towing and work of the three, but GM expects it to provide best-in-class towing capacity, horsepower, and torque. Because of the torque increases in the V-8 engines, new 9.5- and 9.76-inch axles will be used.

The Silverado and Sierra's frame and cab are stronger. The frame's main rails and crossmembers use high-strength steel, as does two-thirds of the cab structure, and major components of the frame are hydroformed. The truck's bed has also been strengthened, using roll-formed steel, reducing mass and increasing strength. One new feature is GM's CornerStep bumper, which seems to be the company's response to Ford's "man step." It has a cutout step in the bumper and handholds in the bedrail to make it easier to access the bed. Also in the rear bumper are four- and seven-pin trailer connectors. Other bed options include an EZ Lift and Lower tailgate, under-rail LED lighting, and new upper tie-down hooks. A new 6-foot, 6-inch-length bed is available with crew cab models for the first time (on a new wheelbase); the longest bed previously offered with the crew cab was 5 feet 8. The third bed length will be the traditional 8-foot longbed. All three bed lengths will be offered behind the regular cab. We anticipate a factory spray-in bedliner will be optional as well.

The truck uses a revised suspension including stiffer springs and aluminum suspension arms in front, retuned leaf springs in the rear, and twin-tube shocks at all four corners. The wheels, which come in 17- to 22-inch sizes, are now wider to improve ride and handling. GM integrated shear-style body mounts to improve ride comfort and reduce noise; extended- and crew-cab models have a third set of mounts. Now, both the Sierra and Silverado have electric power steering -- like the Ram 1500 and most F-150s -- to improve fuel economy, and new four-wheel disc brakes. StabiliTrak with trailer sway control and hill-start assist is standard on all trucks. There are plenty of other safety features as well, including forward collision alert, lane departure warning, and front and rear park assist.

Neither pricing nor an on-sale date were announced, but production will start in the second quarter of 2013. As soon as we hear more details about the new trucks, we'll let you know what we find out.