GMC's light-duty Sierra trucks in half-ton 1500 models include Wideside and Sportside body styles, rear 2WD and 4WD modes, and cabs of regular and extended lengths.

But for 2004 there's more - a new 1500 Crew Cab with four full-size doors and two row of seats for up to six passengers. The Crew Cab comes in SLE or SLT trim and 2WD or 4WD and an abbreviated cargo box measuring 68 inches long. The Crew Cab Sierra draws from a Vortec 5.3-liter V8 producing 295 hp to bring down GVWR numbers of 6800 (2WD) and 7000 (4WD) pounds plus maximum trailer towing capacity of 8500 pounds.

Deluxe Sierra Denali with an all-wheel-drive (AWD) system stocks Delphi Automotive's Quadrasteer, which controls the direction of rear wheels so all four wheels work together more efficiently than when only the front ones turn. Vortec V8 engines in the series range from a base 4.3-liter plant at 200 hp and 4.8-liter at 285 hp to the 5.3-liter with 295 hp and a 6.0-liter V8 worth 300 hp - but in Sierra Denali it's pushed out to 325 hp.

The HD (heavy-duty) label for Sierra signifies big trucks stretched to king-size dimensions. The series shows cabs of regular and extended lengths along with the four-door Crew Cab stocking car-like comforts.

Muscular engines power these trucks to the top of the heavy-duty class, from a big-block 8.1-liter Vortec with 340 hp to a Duramax 6.6-liter turbo-diesel that musters 300 hp. Sierra in 2500 series adds a four-door Crew Cab edition in 2WD or 4WD with GVWR of 8600 pounds, and there's a new 3500 (one-ton) model with single-rear-wheel (SRW) configuration for 4WD and a long-box bed in back with all three sizes of cabs.

GMC's full-size sport-utility vehicle rides on the Sierra platform and totes Sierra powertrains that reach from a 285 hp 4.8-liter V8 to a 5.3-liter edition good for 295 hp. The 4WD Yukon uses an active transfer case and optional Autoride continuously-variable suspension.

A new tire-pressure monitoring system puts a graphic icon flashing in the instrument panel if air pressure drops below a specified level. New options include a power sunroof and DVD-driven video entertainment system with flip-down LCD screen and two sets of wireless headphones.

The XL version has the Yukon structure but with added inches in length and more power. Half-ton XL stocks Yukon's Vortec 5.3-liter V8 rated at 295 hp, while the three-quarter-ton XL gets a 6.0-liter V8 spiked to 325 hp. Further, the big-block 8.1-liter Vortec V8 at 340 hp is available for the largest XL and increases tow rating to 12000 pounds.

Quadrasteer 4WS is optional for Yukon XL 2500, and new communications and entertainment packages range from a DVD-based video player to OnStar telecommunications and XM satellite radio service.

Denali represents the top of the line for Yukon and Yukon XL in deluxe editions outfitted with leather seats, a permanently-engaged AWD system and smooth Autoride suspension.

Power stems from the Vortex 6000 V8, with 325 hp in this installation as mated to an upgraded heavy-duty four-speed Hydra-Matic 4L65-E automatic transmission. In the cabin, three rows of seats in tone-on-tone leather make room for up to seven riders plus cargo space.

Denali in 2004 adds a standard tire-pressure monitoring system and options like a sunroof and DVD entertainment system. The color chart lists new shades such as Silver Birch Metallic and Sport Red.

midsize Envoy returns for 2004 with dual designs, a regular-length version with two rows of seats for five-rider capacity and the Envoy XL, as in Extra Large. It runs 16 inches longer and three inches taller than the standard Envoy with enough extra room in the cabin to apply a third row of seats for two and boost the passenger count to seven. The third row consists of two independent seats set side-by-side.

Each seatback folds down and the entire seat tumbles forward to increase cargo capacity in the rear bay, or the seats may be removed, either separately or together. Access to the third row comes through rear side doors by sliding one of the second-row seats forward, then folding the seatback down and tipping the seat on its front end.

Both Envoy and Envoy XL draw from a standard 4.2-liter in-line-six engine with dual cams and output of 275 hp. Envoy XL also offers a Vortec 5.3-liter V8 good for 290 hp. With the V8 option, XL can tow a trailer weighing up to 7200 pounds in 2WD and 7000 pounds for the 4WD model.

Electrically adjustable pedals are new to Envoy's option list, along with DVD entertainment system.

Latest variation to the midsize Envoy SUV is the Envoy XUV. It's the first SUV with a power sliding roof. Touch a button and the trailing edge of the roof slides away to form an open-air cargo bay. Use that space to transport large and tall goods like a refrigerator, bicycles, even landscaping trees.

A middle gate positioned behind the passenger area includes a power glass window at the top and a composite lower panel. It closes to seal the back bay from the cabin, while the rear section can be hosed out for cleaning. At the tail there's another gate with power window that drops down or the door swings aside.

Engines for the XUV compare to Envoy XL with the straight-six or optional V8.