At first glance, the 2011 Chevrolet Silverado doesn’t appear to have changed much compared to its 2010 counterpart. But don’t let their familiar faces fool you, because virtually all of the greasy bits have been substantially upgraded or replaced entirely. Like the competitive heavy-duty trucks from Ford and Dodge, Chevy offers its trucks in a huge array of configurations with varying passenger, payload and towing capacities and an array of gasoline and diesel engines. We drove seven different variants over two days in the Allegheny Mountains of Western Maryland along with the latest models from Dodge and Ford for comparison’s sake. While the sales volume in the heavy-duty truck segment is smaller than it was at its peak a few years ago, it comprises about 25 to 30 percent of all pickup sales.