The most capable heavy-duty truck in General Motors' line-up, the 3500HD is available with dual rear wheels for serious towing and hauling capabilities. For 2008, the Crew Cab Silverado 3500HDs receive new standard 17-inch wheels.

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Five body / drivetrain styles exist: a Regular Cab 4WD, Extended Cab 2WD or 4WD, Crew Cab with 2WD or 4WD. All could be had with single rear wheels or double. All sport the Long, 97.8-inch box. All body styles are available with one of two engines: a gasoline-fueled Vortec 6.0 liter that makes 353 horsepower at 5,400 rpm and 373 lb-ft of torque at 4,400 rpm thanks to variable valve timing, and a 6.6 liter Duramax diesel developed by Isuzu that puts down 365 horsepower at 3,200 rpm and 660 lb-ft at 1,600 rpm. The diesel is compatible with B5 bio-diesel fuel. Interestingly, Sierra 3500s with a Gross Vehicle Weight Rating of over 10,000 lbs (the dual rear wheel versions) get a 312 hp at 4,400 rpm version of the Vortec 6.0 liter. The torque number remains the same, however.

Transmissions are six-speed automatics, with the diesel engine receiving its own, the Allison 1000.

Anti-lock four-wheel disc brakes, OnStar, a tire-pressure monitoring system, AM/FM/CD/MP3 stereo with four speakers and a 3-month trial subscription to XM Radio are all standard features on all 3500HDs, and are included on the first of four trim levels.

Rear parking assist is a noteworthy standalone option, as is heated windshield washer fluid.

The maximum payload capacity belongs to the Regular Cab 3500 with 2WD and single rear wheels at 4,608 lbs. Opt for the 4WD 'skinny' model and the Extended Cab takes that distinction with a 3,880 lb bed capacity. The strongest dually, is the Regular Cab 4x4 with a bed capacity of 5,307 lbs. The 2WD dually maxes out at 5,127 lbs.

As for towing, ball-hitch maximums are 13,000lbs when the diesel is doing the pulling no matter the body style and drive wheel combination, or 12,600 with a 4.10 axle on the Regular cab 2WD model with the Vortec V8 under the hood.

Equip the 3500 with a fifth-wheel hitch to tow a gooseneck trailer, (only with the 4.10 axle on gas models) and the numbers don't change for the gas-powered truck, but the diesels is capable of a maximum of 16,500 lbs when in regular cab, 4WD, dual rear wheel guise. Towing capacities for the other models jump by at least 1,600 lbs.