Toyota Motor Corp. slipped to third position in U.S. new vehicle sales in September, while the overall market shrank from a year earlier for the first time since May 2011 due to fewer days reported in the month, research company Autodata Corp. said.

Dealers sold 1,139,050 cars and light trucks in the U.S., down 4.2 percent from a year ago, Autodata said Tuesday. This September was two days shorter than in 2012 as the August reporting period stretched to Sept. 3, the day after Labor Day.

The monthly tally translates into an annualized 15.28 million units after seasonal adjustments, down 810,000 from the previous month. But the annualized total stayed above 15 million for the fifth month in a row, suggesting an underlying strength in the new car market as the economy recovers.

Toyota posted a 4.3 percent drop in sales to 164,457 units, dropping to third from second in August. It traded places with Ford Motor Co., which increased sales by 5.7 percent to 184,452 units, backed by strong demand for hybrid models.

Market leader General Motors Corp. lost 11 percent to 187,195 units. Honda Motor Co. slipped 9.9 percent to 105,563 units, falling to fifth from fourth, which Chrysler LLC took after gaining 1.4 percent to 139,860 units.