Big sales of F-150 pickups powered good results for Ford in September -- and big profits that may have come at GM's expense. Will those gains continue? Photo credit: Ford Motor Co.

Ford (F -0.35%) made solid gains in a tough U.S. market in September, thanks to strong sales of its F-Series pickups. Many of those sales came at the expense of old rival General Motors (GM -0.40%), as many buyers shied away from GM's all-new Chevrolet Silverado.

Was that a one-month fluke, or the start of a new trend? In this video, Motley Fool contributor John Rosevear looks at the latest analyst reports on the state of the U.S. auto market, and predicts how Ford and GM will fare when the latest sales numbers are released this Friday.