DETROIT — Big pickups carried U.S. auto sales to their highest level in three years. Demand for full-size pickups jumped 16 percent in August, helping to make it the strongest sales month since August 2009. Overall auto sales increased 20 percent from a year earlier to nearly 1.3 million, according to Autodata corp.

The rising demand shows that businesses need to replace aging trucks and feel more confident about the recovery in U.S. housing — an industry where pickups are essential for hauling equipment and crews.

“Businesses don’t usually go buy a fleet of trucks unless they have good reason to believe that business will be ramping up,” said Jesse Toprak of the TrueCar.com auto pricing service

Ford, GM and Chrysler, the biggest makers of full-size trucks, notched double-digit gains in overall sales last month. In pickups, Ford’s F-Series, the top-selling vehicle in America, saw a 19 percent sales increase, as did Chrysler’s Ram pickup. Sales of General Motors’ Chevy Silverado rose 4 percent, while the GMC Sierra was up 9 percent. Toyota’s struggling big truck, the Tundra, posted a huge increase of 68 percent.

The rising demand helped push total U.S. auto sales last month to an annual rate of 14.5 million. That’s the best sales pace since the government’s “Cash for Clunkers” program in August of 2009.

Pent-up demand is part of the reason for last month’s truck increase. The average vehicle on U.S. roads is nearing 11 years old, and some are simply wearing out. But automakers and industry analysts say the economic recovery — new housing in particular — is also starting to make buyers feel more comfortable about a big-ticket purchase.