Helped by Americans’ ceaseless demand for pickup trucks, Ford Motor said Tuesday its U.S. sales jumped 5 percent in August, its best performance for that month since 2007. Fiat Chrysler Automobiles’ sales increased 2 percent with the help of Ram trucks, while General Motors reported a 1 percent drop but big gains in Silverado and Sierra sales.

“Improved availability helped make August the strongest sales month this year for F-Series,” Mark LaNeve, Ford’s head of U.S. sales, said in a statement. “We also had our best month of Ford SUV sales in 12 years.”

Sales of America’s most popular pickup trucks made by the three North American automakers increased 8 percent last month.

Ford’s F-150 truck sales got off to a choppy start this year as the automaker had to retrofit its assembly lines making the 2015 F-150, the first aluminum-body Ford pickup truck, because aluminum and steel have to be fabricated differently. Last month, F-Series truck sales (which include a small number of heavy duty trucks, like the F-350) increased 5 percent to 71,332 units, mostly on demand for the new F-150.

Overall U.S. truck sales are booming and, along with SUVs, have carried the U.S. auto market through what will become the sixth consecutive year of growth since the 2009 economic downturn. Total U.S. new car sales are in line to top 17 million in 2015 for the first time since 2001, when sales hit 17.2 million.

Fiat Chrysler Automobiles said Ram pickup truck sales jumped 4 percent last month to 45,310 units, while General Motors reported a 10 percent jump in Chevrolet Silverado and GMC Sierra truck sales, to 69,048. The Silverado and Sierra are mechanically identical, with the pricier Sierra offering more luxurious interior options.

The F-150, Silverado and Ram 1500 trucks are the three best-selling models in America.

Automakers release their U.S. sales numbers throughout the day Tuesday. Forecasters expect U.S. new auto sales to have dropped by as much as 4 percent in August to roughly 1.53 million units, compared with the comparable month last year. The annual Labor Day sales weekend, one of the biggest new car sales events of the year, lands in early September this year instead of late August.

“Last August was a monster month that included Labor Day weekend,” Jessica Caldwell, director of industry analysis for automotive shopping site, said in a statement.