The Sierra is built on a stiff platform for a smooth ride and sharp handling.The GMC Sierra shares platforms with the Chevy Silverado but its exterior styling is quite different.

Sierra interiors offer a choice of two dashboard styles.The traditional layout, called pure pickup, has a driver-oriented dash layout with larger switchgear and door handles designed for work gloves.The pure pickup interior includes a 40/20/40 split front bench seat with the center section folding down to provide a large storage compartment and wide armrest.The other style in the luxurious Sierra SLT is similar to what's found in the latest luxury SUVs, with two front bucket seats separated by a fixed center console.This design places audio and ventilation system controls more easily within reach of the front-seat passenger, which may or may not be a spouse, and it offers a navigation system and storage compartments.

The new Sierra Hybrid uses GM's new Two-Mode Hybrid system first launched in the 2008 Yukon Hybrid.The Sierra Hybrid is a Crew Cab model with a specially tuned 332-hp 6.0-liter V8 working in conjunction with a battery pack and a four-speed automatic transmission that houses two electric motors.The Hybrid offers fuel economy ratings in the 20-22 mpg range, while compromising payload and tow capacity (maximum around 6000 pounds).

The 2009 GMC Sierra Denali makes for a comfortable, luxurious pickup with the emphasis on performance rather than payload and towing capacity.The Sierra Denali offers the same sort of high-line content as the upscale GMC Yukon Denali sport utility.Sierra Denali comes with all-wheel drive.

The 6.2-liter V8 used in the Denali is also available in regular trim Crew Cab pickups with four-wheel drive for more power and fuel consumption.

Sierra offers many permutations with a choice of cab styles and bed lengths, and nine engine choices (of five sizes).There are limitations however, such as the biggest engine is limited to Crew Cabs, the 6-liter does not go in regular cab or extended cab long bed trucks, and manual transmissions are not offered.

The extended cab has two rows of seats with rear-hinged rear access doors that open 170 degrees and have roll-down windows.The extended cab can be equipped with either a short bed (5-foot, 8-inch), standard or long bed.The extended cab can be equipped with seating for five or six.

The Crew Cab has two rows of seats and four front-hinged doors, like those on a Yukon.The Crew Cab can be equipped with seating for five or six and comes with the short bed.

Standard equipment on the basic WT 1SA work truck ($18,045) includes vinyl seating surfaces, air conditioning, AM/FM/XM radio, one-year of OnStar, daytime running lights, tire pressure monitoring system, Smooth Ride suspension, 17-inch wheels, automatic transmission and chrome bumpers.

SLE ($25,575-$33,375) adds cloth seats, CD player, cruise control, rear-window defogger, auto-dimming rearview mirror with compass and outside temperatures, leather-wrapped steering wheel, fog lamps, handling/trailering suspension, carpeting and power door locks/windows/mirrors.Additions include premium cloth seats, dual-zone air conditioning, a floor console, six-way power driver and front passenger seats, audio controls on the steering wheel, and machined aluminum wheels.

SLT ($33,580-$40,575) adds leather seat trim, a unique instrument panel, six-disc CD changer with Bose sound system, heated windshield washers, front bucket seats with 12-way power adjustment and heat, and polished aluminum wheels; crew cab models also get a rear-seat audio system.

Denali ($42,740) includes a top-flight interior with leather, heated and powered front seats, unique woodgrain console, side curtain airbags, dual-zone climate control, park assist and so on.Denali options include a heated steering wheel, heated/cooled front seats, sunroof, and rear-seat entertainment.Denali comes only as a Crew Cab with a 403-hp 6.2-liter V8 engine, six-speed automatic transmission and rear or all-wheel drive.

All Terrain model features the Z71 off-road package, heavy-duty trailer package, 18-inch wheels, Rancho shocks, and myriad cosmetic enhancements.When ordered with SLT trim, exclusive two-tone leather is used.All Terrain is available as an extended cab standard box or crew cab, 2WD or 4WD with 5.3-liter or 6-liter engine.

Sierra Hybrid, Crew Cab only, uses a specially tuned 332-hp 6-liter in conjunction with a battery pack and four-speed automatic transmission that houses two electric motor units.With EPA ratings in the 20-22 mpg range its urban economy is the best of the Sierras, the compromises being price, payload (max mid-1400-pound-range) and maximum tow capacity around 6000 pounds.

Options include a locking rear differential, StabiliTrak, towing and trailering equipment, and a power sunroof.

Safety features include dual front airbags and a tire-pressure monitoring system.Optional head curtain airbags automatically inflate when sensors sense a severe impact to provide extra protection in the event of a rollover or secondary collision.Also available: driver and front-seat passenger side-impact air bags; anti-lock brakes, StabiliTrak electronic stability control with rollover mitigation technology, Autotrac active transfer case, ultrasonic rear park assist, OnStar emergency notification.

Top trim levels get some distinguishing features.The Denali gets its own chromed grilles, both the upper section and the air vent below the front bumper, and the bumpers are painted to match.Hybrid models are festooned with odd-looking H badges.

The Sierra hood has a pair of long, narrow V-shaped power bulges and leads back to a steeply raked windshield.The windshield is tilted back for improved aerodynamics and enhanced highway fuel economy.

The side view features slightly bulging and elongated fender flares that sweep down behind the headlamps.The sides of the cargo bed are higher than on previous models, and the exterior of the tailgate is sculpted, enhancing the rear view of the truck.Stacked tail lamps are on either side of the tailgate.

A cargo management system is available for the bed with side rails and various cargo-carrying and cargo-controlling boxes and dividers and tie-downs.

The GMC Sierra and Chevy Silverado are built on the GMT900 platform that debuted in 2007 and shares many underpinnings with the Yukon, Suburban, Tahoe SUVs.The pickups get a unique rear suspension and frame section that is 245 percent stiffer.The Sierra and Silverado share mechanical components, with the exception of the unique features found on the Sierra Denali.

Compared with the previous-generation (pre-2007) models, the current frame is 234 percent stiffer in torsional rigidity, 62 percent more resistant to bending and 136 percent stiffer laterally.This yields a smoother ride and better handling.It also allowed the engineers to reduce the gap between the truck bed and passenger compartment as well as the gaps between fenders and bumpers, all of which enhances aerodynamics and fuel efficiency.

The front suspension uses a coil-over-shock setup and the rack-and-pinion steering gear is mounted to the engine cross member frame.The truck also has a new rear axle design with shocks absorbers mounted outboard and more upright for better dynamic control.

Engine choices include a V6, a 4.8-liter V8, four 5.3-liter V8s (iron and aluminum blocks, some E85 flex-fuel capable, all with Active Fuel Management that disables some cylinders for fuel economy), a 6-liter V8, most with four-speed automatic transmissions moving to six-speed autos, and a 6.2-liter with six-speed automatic.Except for Hybrids and the 6.2-liter, EPA ratings run 13-15 mpg City, 17-20 mpg Highway, and on E85 those numbers drop substantially.

A late addition to the 2009 lineup are XFE (Xtra fuel economy) models with a 5.3-liter V8, six-speed automatic and axle ratio of 3.08:1 that increase EPA ratings form 14/20 to 15/21.Proprietary XFE pieces include aerodynamic upgrades in the form of a soft bed cover and extended front air dam, plus aluminum wheels (including the spare) and lower front suspension arms, locking rear differential, and low rolling resistance tires.A trailering package is standard so XFE models can tow up to 7000 pounds.

The pure pickup, as it's called, has a unique dashboard that is more driver-oriented and has larger switchgear and door handles that are designed to be easily manipulated by those wearing work gloves.The pure pickup interior includes a 40/20/40 split front bench seat with the center section folding down to provide a large storage compartment and wide armrest.

The SLT's SUV-style luxury-oriented interior puts audio and ventilation system controls more easily within reach of the front-seat passenger and has two front bucket seats with a fixed center console with assorted storage compartments.

Either dashboard sports full analog instrumentation, and many have more info available through digital display.Operating controls are GM simple, especially on the pure pickup, while the top-line models central dash has many small white-on-black buttons that may require a short learning curve.Some drivers report peculiar ergonomic details as the steering wheel is slightly offset from the seat centerline (which is not uncommon).

Rear seating is provided for three people in the extended and crew cab versions, with 34.3 inches of rear legroom in the extended cab and 38.7 in the crew cab, space is similar to Ford's F-150 and Nissan's Titan, and smaller than Dodge's Quad and Mega Cabs and Tundra's Double and CrewMax cabs.The crew cab rear seat is split 60/40 and can folded up individually for a flat load floor; this arrangement is optional on extended cabs.

Access to the rear seating area of the extended cab is eased by rear-hinged doors that open to nearly flush with the bed sides.Sitting in the back seat of the extended cab is made more pleasant thanks to the fact that the windows in the rear access doors power fully down.

The 5.3-liter V8 provided plenty of power for the extended cab SLE models we drove.And the 6.0-liter V8 was more than enough for the SLT Crew Cab we checked out.All engines need to be revved up (by truck standards) for best grunt.Generally the Sierra models match competitors for smoothness, though by benefit of their five-speed automatics the Ram 4.7 typically runs with GM's 5.3, the Ram 5.7 and Titan 5.6 compete with the GM 6.0, while Tundra's 5.7 and six-speed auto performance can be matched only by the 6.2 and six-speed auto.

If you want better fuel economy but want more towing capacity or acceleration than the XFE models provide, adjustments to driving style can easily return the same 5-percent increase in city or towing mileage.In other words, we're not sold on the gearing of the XFE.

Of the suspensions, the Z83 is claimed the smoothest ride.The Z85 is slightly stiffer and for those who often tow moderate trailers, a good choice for towing.The Z71 is set up to enhance off-pavement driving yet works very well on the road.In fact, we think the Z71 is the best suspension setup for comfort on the widest range of surfaces.The Z60 configuration is for street performance and includes big 20-inch wheels; we're all over performance but think trucks should be trucks, so the Z60 is not our first choice.The NHT package is designed for Sierra owners who need to tow and carry the heaviest loads.

With NHT, the SLT Crew Cab 4x2 is equipped with the VortecMax 6.0-liter V8 engine, and a 3.73:1 rear axle.Ours was fitted with StabiliTrak, side-curtain airbags, a locking rear differential, and a convenience package that includes adjustable pedals, remote vehicle starting system and rear park assist.The SLT with NHT suspension is designed for maximum capacity trailer towing, with a special steering gear, shock absorbers, rear axle and tires.We found the NHT suspension compliant relative to its carrying capacity.Isolation and control are both very good.By virtue of its fairly stiff spring and shock rates, the NHT suspension can be driven aggressively on winding roads with tire squeal the primary indication you're approaching limits.Steering is direct by truck standards and nicely weighted, providing good feedback about how hard everything is working though the assist can fall behind during repeated full-lock maneuvering as when backing a trailer.However, if you drive empty and don't tow, we don't recommend the NHT package just so you can have the 6-liter V8 due to its harsher ride.

All new Sierras benefit from much improved brakes over earlier models, whether they have the rear discs or drum brakes.

The integrated brake controller that's available should find favor with drivers who tow RV or box trailers.However, be sure your trailer brakes are compatible with it before choosing the option, as some electro-hydraulic disc conversions do not work with the integrated controller.If it is compatible, it's a great feature, eliminating the mess of installing an aftermarket unit and offering more precise braking.

The highest tow rating for a Sierra is 10,700 pounds on extended cab (not long bed) or crew cab model; top regular cab rating is 9200 pounds.Note these figures typically apply to a truck with just a driver on board, and vary substantially based on a variety of equipment and options.

G.R.Whale test drove various Sierra models and filed this report to NewCarTestDrive.com from California; with Larry Edsall reporting from Phoenix.