Major automakers posted double-digit U.S. sales gains for August from year-earlier levels, a steady result for a month that began with a plunge on Wall Street and ended with a hurricane shutting down the East Coast.

General Motors Co reported a sales gain of 18 percent, slightly below some analyst expectations. Ford Motor sales were up 11 percent. Chrysler had its best August sales in four years with a 31 percent sales increase.

Auto industry executives said the sales gains pointed to an encouraging stability in demand for big-ticket purchases in the face of renewed economic uncertainty.

In our view, consumers are being cautious, yes, and rightly so, but they are not retrenching, said GM's head of U.S. sales, Don Johnson. You have to remember that the sales we're seeing are very low by historical standards.

Sales for Nissan Motor Co rose 19 percent. Sales for Volkswagen AG were up 10 percent.

GM estimated that industrywide U.S. auto sales would be about flat from July when adjusted for seasonal factors and tracked on an annualized basis.

(Reporting by Bernie Woodall and Kevin Krolicki, editing by Matthew Lewis)