GMC Sierra HD

GMC gets an all-new line of heavy-duty pickups in 2007. More than mere re-styling, the 2007 GMC Sierra 2500HD and 3500HD also get a boost in the one department where they might have been considered lightweight in today's hyper-competitive market: powertrain.
Benefiting from variable valve timing, the base engine for 2007 is a new 6.0-liter V8 making 353 horsepower and 373 pound-feet of torque, increases of 53 hp and 13 lb.-ft. over the '06 6.0-liter V8.

The top engine, a much re-worked version of the tried-and-true Duramax 6.6-liter V8 turbocharged diesel in the 2006 GMC HDs, ups its output to 365 horsepower, vs. the '06's 360, and the torque to 660 pound-feet, vs. the '06's 650. It's also cleaner, emitting 90 percent fewer particulates and 50 percent less NOx than the current version, bringing the engine into compliance with government clean air standards set to take effect in calendar year 2007.
Each engine is paired with its own, new, six-speed automatic transmission. The gasoline-fueled V8's Hydra-Matic offers a manual-shift, tap-up/tap-down gear selection mode. Two-wheel drive is standard, four-wheel drive optional.