Strong sales of new models like the 2014 Chevrolet Silverado have helped boost GM's shares this year, despite heavy selling by the government. Photo credit: General Motors Co.

Shares of General Motors (NYSE:GM) hit a 52-week high last week. The stock jumped nearly 5% after the U.S. government said that it had sold $1.2 billion worth of GM stock in October. Over the last year, GM's stock has risen roughly 60%, despite heavy selling by the U.S. Treasury as it unloads the huge stake it received in the wake of GM's 2009 bailout.

But why would that make GM's stock jump? As Motley Fool contributor John Rosevear explains in this short video, it's because the end of the "Government Motors" era is in sight. But as John notes, that end will bring a major new challenge for GM's management.