Toyota Motor (TM 0.55%) reported that U.S. sales in September jumped more than 40% from a year ago, to 171,910 units. The Chrysler Group, owned by Fiat, also reported a surge in U.S. sales in September and reported the highest revenues in that month the company has had since 2007. However, the two largest domestic car manufacturers, General Motors and Ford Motor (F -1.42%), reported September results that weren't nearly as impressive. GM posted a meager 1.5% increase in total sales, but revenues from its passenger cars rose almost 30%. Ford sales were unchanged.

For GM and Ford, what dragged down growth was the sluggish performance of pickup truck sales. In GM's case, its truck sales were down 20% in September. Ford reported an 8% decrease in revenues from its pickup trucks, mainly because it discontinued the Ranger series in the U.S.

Auto sales may be climbing because people are driving outdated vehicles and are being forced to upgrade, according to The Wall Street Journal. GM and Ford are hoping to pick up some momentum in October, which they've dubbed "truck month," the Journal reports.

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