Entering the seventh year in its current guise, this generation of the GMC Sierra 3500 gains the word "Classic" in its name to help differentiate it from a fully redesigned Sierra 1-ton that debuts later in the year. Despite the Classic's age, all of the traditional strengths of this big GMC truck still stand, such as handsome styling and a lineup of impressively capable powertrains.

Though the 2007 GMC Sierra 3500 Classic pickup is pretty much unchanged, GMC did make a number of revisions last year. They included some major upgrades to the optional Duramax diesel engine that provided the truck with best-in-class power ratings of 360 horsepower and 650 pound-feet of torque. As if that wasn't enough, the Allison automatic transmission was upgraded with an extra gear for a total of six. It's another overdrive gear designed for maximum fuel economy on the highway.

That strong combination puts the GMC head and shoulders above the competition when it's time for some serious towing. Some of the less flattering aspects of this outgoing workhorse are its lack of key safety features like side airbags and stability control, and questionable fit and finish inside the cabin.

The Sierra's immense capabilities, classic styling and many available features make it our favorite heavy-duty pickup truck overall. You can't go wrong with any of the powertrain choices, as they all provide strong performance and respectable towing capacities. But if you're very serious about towing heavy loads, you'll want to spec out a truck with the Duramax diesel and dual rear wheels. Thusly equipped, the 2007 GMC Sierra 3500 Classic is unfazed by massive payloads and heavy trailers.

A variety of cab and bed styles are available for the 2007 GMC Sierra 3500 Classic full-size pickup truck. There are regular, extended cab and crew cab body styles, and all come with 8-foot boxes with either a single or dual rear-wheel configuration (except the regular cab 2WD, which is single rear-wheel only). There is also a choice between two- and four-wheel drive for all body styles. There are four trim levels: bare-bones Work Truck, base-model SL, midgrade SLE (which actually has two subsets: SLE1 and SLE2) and luxury SLT. Work Trucks are pretty basic but have dual-zone air-conditioning, a 40/20/40-split bench seat, a tilt steering wheel and AM/FM radio. The SL adds amenities like upgraded upholstery, cruise control and a CD player, as well as chrome trim for the grille and rear bumper. The SLE1 trim has power windows and locks, remote keyless entry and foglamps, while the SLE2 adds automatic climate control, Bose audio and a power driver seat. The range-topping SLT features aluminum wheels and leather upholstery. Major options for lower trims include power locks and upgraded cloth seating, while uplevel SLE and SLT trims allow access to OnStar, a rear-seat DVD entertainment system, a sunroof and satellite radio.

The 1-ton Sierra Classic's engine lineup starts with the 6.0-liter V8 (300 hp, 360 lb-ft of torque). If that's not enough, consider the optional 8.1-liter V8 (330 hp, 450 lb-ft of torque) or the even stouter 6.6-liter Duramax diesel V8 (360 hp, 650 lb-ft of torque). The 6.0-liter V8 has a five-speed manual standard, with a heavy-duty four-speed automatic optional. The 8.1-liter V8 and the Duramax diesel come only with the six-speed Allison automatic. When it's time to work, the Sierra 3500 Classic is more than capable of hauling heavy loads. Equipped with a regular hitch, a dual-wheel 3500 can pull a 12,000-pound load. Utilizing a fifth-wheel trailer raises the limit considerably.

Antilock brakes are standard and traction control is optional. But several state-of-the-art safety features, such as stability control and side curtain airbags, are not available. In NHTSA frontal-impact crash testing, the Sierra Classic received a rating of four stars (out of a possible five) for the driver and three stars for the front passenger.

Make no mistake; trucks of this ilk are happiest when working. Performance is strong and seamless, especially with the Duramax engine option. And the 2007 GMC Sierra 3500 Classic is stable when working -- with the bed loaded, the pickup truck remains composed, with minimal sway on curvy roads, even in heavy crosswinds. Around town, the Sierra's ride is comfortable enough for daily-driver use, but on the highway with an empty bed, it can get jittery over expansion joints, due to the stiff suspension calibrations required to handle heavy loads. Though it tracks straight and corners fairly well, steering feel is basically nonexistent -- there's little feedback in a straight line and it's not much better through corners. Likewise, the brakes have a non-linear feel through the pedal, despite being quite effective when it comes to actual stopping distances.

Clear gauges, simple controls and comfortable seats are the strong points of the Sierra's cabin. There is plenty of room for six passengers, the seats are comfortable and the crew cab configuration makes for easy entry and exit. Downsides include mediocre materials and inconsistent build quality. Long trips are easy to take, thanks to effective sound insulation and the availability of satellite radio and a DVD entertainment system.