The redesigned 2014 Chevrolet Silverado and GMC Sierra full-size pickup trucks were unveiled Thursday morning, ahead of their debut at the Detroit Auto Show in January. At first glance they look like General Motors pickups, carrying over many of the basic styling themes of the current-generation trucks that were launched six years ago.

But under the skin, the trucks have been thoroughly reworked with a lighter but stiffer frame and cab, modern interior with video screens and wireless connectivity, and a trio of new engines--one V6 and two V8s--from the fifth generation of GM's small-block engine family that uses cylinder deactivation for better fuel economy.

The engines use the EcoTec3 brand and incorporate the same technologies as the first engine from the new-generation small block family, the 6.2-liter LT1 V8 for the redesigned 2014 Chevrolet Corvette. GM has said the LT1 will make at least 450 hp.

Those technologies are:

-- Direct fuel injection, which puts the fuel directly into each cylinder.

-- Continuously variable valve timing, which adjusts the opening and closing of the valves based on engine load.

-- Cylinder deactivation, which shuts down some of the engine's cylinders under light loads. In the trucks, the system turns the V6 and V8 engines into V4s. GM says it has expanded the range within which the system, called "active fuel management," is engaged.

All three of the truck engines--a 4.3-liter V6, 5.3-liter V8 and 6.2-liter V8--use aluminum blocks and cylinder heads, which helps reduce weight compared with iron blocks and heads. The new GM trucks all use six-speed automatic transmissions. Many of the current trucks were equipped with four-speed automatics.

GM has yet to release horsepower and torque ratings for the new engines but promises that the 4.3-liter V6 will be capable enough for towing duty. The V6 will be available in the trucks' large, crew cab configuration. GM's current pickups use a 4.3-liter V6 as the base engine, rated at 195 hp and 260 lb-ft of torque. It would not be surprising if the new V6 is rated close to the current 4.8-liter V8, which puts out 302 hp and 305 lb-ft of torque.

One thing not on the new GM truck engines: forced induction via a turbocharger or supercharger. That makes the base engine in the GM trucks a distinct alternative to the Ford F-150 and its turbocharged EcoBoost V6. The Ram 1500 also offers a V6, mated to an eight-speed automatic transmission, for higher fuel economy.

Better aero, more comfort

Both trucks get a new twin-port grille and full-width bumper, along with a more sculpted overall look. The GMC Sierra is slightly taller than the Chevy Silverado, has projector beam headlights, chrome accents and moldings on the wheel wells.

Integrated into the rear bumper is a corner step for easier access to the bed--a feature first used on the soon-to-depart Chevrolet Avalanche--along with handholds. The bed can also be equipped with new upper tie-down hooks, under-rail LED lighting and an easy-lift-and-lower tailgate.

To boost fuel economy, engineers focused on weight reduction and improved aerodynamics. Redesigned door mirrors, triple-sealed doors inlaid into the body, roof and tailgate design features smooth the flow of air over the trucks. To cut weight and boost rigidity, two-thirds of the truck cab and the frame's main rails and key cross members are made from high-strength steel. Another fuel-saving move is the switch to electric variable-assist power steering, which GM says improves overall vehicle handling and reduces steering effort at low speeds.

Interior highlights include an upright instrument panel, six-gauge instrument cluster with an optional center-mounted 4.2-inch information center that shows vehicle status information, and multiple storage options. Knobs are coated using a rubber over-mold technology so they're easy to grip, even while wearing gloves. Premium materials are added to the GMC Sierra's cabin, including more soft-touch materials and an optional aluminum trim.

Getting in and out of the pickups is easier. The rear doors on crew cabs are larger, and the rear doors on extended-cab models are now hinged at the front so they can be opened independently of the front doors. The B-pillar of crew cab models was moved forward, and the rear seat redesigned to add about 2 inches to rear legroom.

The pickup box on regular cab models is available in three lengths--5 feet, 8 inches; 6 feet, 6 inches; and 8 feet. Crew cab models add the 6-foot-6-inch box as a new option, in addition to the 5-foot-8-inch box. The extended cab truck can be configured with the 5-foot-8-inch or 6-foot-6-inch.

The doors have storage for beverages, and along the center stack and center console are additional cupholders, discreet compartments large enough for laptop computers and connectivity options. The Sierra is available with a 110-volt outlet, up to five USB ports, four 12-volt outlets and an SD card slot.

Available safety features include collision alert, lane departure warning with an active safety seat and park assistance. StabiliTrak with trailer sway control and hill start assist is standard.

Production of the 2014 Chevrolet Silverado and GMC Sierra is set to start next spring.

-- Angie Fisher

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