2008 GMC Sierra HD Review

With many models over 7,000 pounds empty, the Sierra HD is a lot of mass to move around, and while the new 6-liter has broadly the same horsepower as the old big-block, torque is down roughly 80 lb-ft. Torque is what gets any load moving, up to about 45 mph, and helps keep it moving on grades. However, the six-speed transmission makes up for a lot, so the absence of a big-block is most noticed in low-range 4WD and the less-forceful shove in your back when you leave a traffic light. The 6.0 and six-speed automatic will do about 90 percent of what the 8.1-liter did, and generally use a bit less gas in the process. Remember however, that horsepower on the dual-rear wheel 3500 6.0 is lowered to 312 hp, making an even better argument for the diesel.

With 660 lb-ft of torque available at a much lower engine speed and 365 hp, the Duramax turbodiesel option blows the 6-liter into the weeds for pulling power and fuel economy, though you might say at $8400 for the powertrain it ought to. Much of the added expense from last year is due to the new emissions requirements for diesel engines, reductions of 90 percent in some cases, and the diesel exhaust pipe stays clean and steel-colored inside where the gas engine's is black. The next generation of induction systems has also made the diesel much quieter; your riders may not know it's a diesel if you don't tell them.

Pickups of yore tended to buck like broncos on uneven surfaces like turnpike expansion joints, with the bed trying to bounce one direction and the cab the other. Often a function of wheelbase, this can't be completely eliminated in a long vehicle like a Sierra HD, but it does an admirable job of mitigating the motion.

There's heft to the feel of a Sierra, from the way it takes big bumps to the steering and throttle inputs. Its handling characteristics are benign and amount to basic plowing if you push too hard. All-terrain tires give better grip on dirt roads, at the expense of steering precision and noise on tarmac.

Like all big 2WD pickups the Sierra uses all-vented disc brakes with ABS, and independent front suspension. However, only the GM heavy-duty pickups use the same design on 4WD models, giving them a lower nose and more responsive steering. Again, like any big pickup, the tail is prone to kick over impacts with an empty bed; the Sierra is similar to others although it may feel it has more kick because the front is softer.

The optional integrated trailer brake controller will apply your trailer brakes smoother than any aftermarket controller and works in concert with the Sierra's braking system. This controller, however, is not compatible with all brands of electric-hydraulic disc brakes becoming more common on high-end RVs.

The 2.5-inch receiver hitch allows conventional trailer ratings to 13,000 pounds, higher than many competitive offerings; the maximum for fifth-wheels 16,700 pounds. The strongest Sierra HD will haul 23,500 pounds gross combined: the truck, fuel, passengers, cargo, and trailer.