Things don't usually happen this quickly in the truck world. The typical product cycle time for a pickup is about seven years, yet in the case of the Silverado/Sierra HD, the time between new models has been pretty short--about four years--motivated by tough new emissions standards. And with the push on to make a diesel-powered truck meet the new federal requirements, the engineers took the opportunity to upgrade the rest of the truck while they were at it.

You can see from the photos that the new generation of Silverado/Sierra HD hasn't changed that much visually. In fact, you can count the number of major differences in styling between the 2010 and 2011 on one hand: a louvered hood, new front bumper and grille, and, for the first time, 20-inch wheels. But don't be fooled by the near-carryover body--when the economy went south, budgets were cut and things quickly changed at GM. The guys working on this project had to prioritize, and spent more resources on improving the function of the truck than updating the styling (see sidebar). So instead of looking at all-new sheetmetal, the result is a truck that's much more capable than ever before, with more power and dramatically lower emissions. Your neighbor might not know this is an all-new pickup, but you certainly will.

The Silverado/Sierra HD is powered by a choice of two engines: a gas 6.0-liter Vortec V-8 or a 6.6-liter Duramax turbodiesel V-8. As of press time, SAE testing hasn't been completed on either engine, so horsepower and torque numbers aren't yet available--but we expect both to be higher on both V-8s. The Vortec is backed by a Hydra-Matic 6L90 six-speed automatic; the Duramax uses an Allison 1000 six-speed auto. The 6.0-liter receives a new camshaft profile, said to help the engine produce more torque lower in the powerband. The big news, though, is with the diesel.