"Two weeks ago, Chevy engineers were spied testing a large group of 2014 Silverado prototypes. That test group has now reappeared, but this time, test vehicles for the all-new GMC Sierra have come along for the ride!
"Fortunately, during one of the many pauses in testing, a Sierra prototype pulled right alongside a Silverado prototype, making the difference between the two trucks easy to see."
In the first photo in this set, the Silverado prototype in the background has one large crossbar running through the middle of the grille opening, while the Sierra prototype in the foreground has at least two thinner crossbars and a few thin vertical bars.
In addition to the difference in grille, visible on several of the prototypes, the Sierra test trucks are also wearing some familiar GMC wheels, with one truck sporting a set that looks almost identical to wheels on the recently debuted 2013 GMC Acadia.
Under the hood of the Sierra 1500 will be the new Gen V small-block V-8. It is said to be an aluminum block and will feature direct injection and cylinder deactivation. A V-6 will also be offered, but exactly which one remains a mystery. It could be the 3.6-liter V-6 found in many other models, but we know GM is also working on a turbocharged 3.0-liter. Given Ford's success with the EcoBoost F-150, we believe GM will want to match it.
A Sierra 1500 Hybrid will continue to be offered for the next-gen models, but at least one industry source has it as a V-6-based hybrid powertrain instead of the current V-8 model. We're also hearing that the hybrid model may not be ready initially at launch.
Power for the heavy-duty models should come from updated versions of the 6.0- and 6.2-liter gas engines and the 6.6-liter Duramax diesel.
An eight-speed transmission is also in the works, but it may not be ready for the initial launch. The transmission may also see use only in the light-duty 1500 models.
The 2014 Sierra is scheduled to begin production as late as April 2013 at assembly plants in Flint, Mich., and Fort Wayne, Ind.