DETROIT, Michigan - General Motors has hired a top gun from Volkswagen to lead the marketing of its most important brand.Tim Mahoney, VW's chief product and marketing officer since 2011, will start on April 1 as global head of marketing for Chevrolet. He'll also be responsible for overall co-ordination of GM's global marketing, the company said.General Motors' top marketing post has been vacant since July 2012 when the company forced Joel Ewanick to step down. Its marketing efforts so far have failed to boost US sales substantially; the automaker reported a four percent US sales increase in 2012 while overall US auto sales rose 13%.20 NEW MODELSVW, on the other hand, has seen sales grow across the globe, especially in the US - almost 31% in 2012.GM chairman and CEO Daniel Akerson said recently that marketing would probably be done by each of GM's brands rather than by the parent company but it was unclear if Ewanick's position would be filled. Mahoney will report to US sales and global marketing chief Alan Batey.Mahoney will be expected to implement Chevrolet's new marketing platform with the tagline "Find New Roads". 2013 will be important for Chevrolet - by far GM's largest brand - with plans for 20 new models worldwide.Mahoney has also worked for Subaru America and Porsche of North America.