Our spy photographer snapped these photos of the 2014 Chevrolet Silverado out testing. Beneath the testing camo, Chevy's characteristic cross-bar grille and bowtie are visible. Perhaps the biggest exterior change is the change of door configuration on the extended-cab models from rear-to-front-hinged rear doors, following in the footsteps of the Ram Quad Cab, which has employed that configuration since 2002. The full crew-cab models appear to have a generously sized rear passenger compartment, even approaching the Ram Mega Cab's proportions.

The 1500 and 2500 HD models can be distinguished from each other by their characteristic six and eight-lug wheels, and the beefier frame on the HD model. The large, canister-like muffler or particulate trap seen on the HD model indicates it's the Duramax diesel, which has been a popular option in the HD models since its introduction in 2001, comprising the majority of sales for the HD series.

As is typical for GM test mules, the headlights and taillights are black plastic units that may not be indicative of the final styling of the production models, although the vertical "stacked" headlights of the current Silverado look like they will carry over to the new model.

The 2014 full-size trucks are expected to debut GM's new fifth-generation small-block V-8s with direct injection. Exact displacement on the new engines is unknown. Some believe the current displacements will continue, while others suggest the engines may be downsized slightly due to the expected higher specific output enabled by the direct injection and higher compression ratios. Following crosstown rivals Ford and Ram, the ancient 4.3-liter pushrod V-6 will likely finally be retired, probably in favor of the 3.6-liter direct-injected V-6 as the base engine, with a turbocharged V-6 option along the lines of Ford's EcoBoost as a possible new addition. Half-ton models are also expected to get a new eight-speed automatic transmission for a significant improvement in fuel economy.

The HD diesel models will likely stick with the current six-speed Allison transmission, though the gas-powered HD models may get the new eight-speed, or stick with the proven Hydra-Matic 6L90 six-speed automatic.