Chrysler sales fell 34 percent in August and are down 24 percent for the year. At GM, sales were down 20.4 percent while Ford sales fell 26.6 percent.
Ford and GM plan production cuts and GM will extend its employee pricing sales promotion through September.
The sale program includes nearly all 2008 model year vehicles and has been expanded to include most 2009 model year vehicles already on dealership lots.
Automakers increased their sales incentives about 7 percent in August from a year earlier, to an average of $2,642 per vehicle with most of the incentives available to consumers going on large trucks and SUVs.
Chrysler led major automakers in incentives with an average of $4,366 per vehicle followed by Ford with $3,443 on average per vehicle.
Toyota's sales dropped 9.4 percent. Nissan posed a surprise 13.6 percent increase in August sales.
Toyota's biggest losses in August came in SUVs, down 24.8 and pickups, off 17.6 percent. Tacoma sales fell 17.8 percent.
American Honda reported a 7.3 percent decline from August 2007. Honda still came within about 5,000 vehicles of passing the Ford, Lincoln and Mercury brands in August.
The August sales numbers are more proof of a consumer shift to smaller, more economical passenger cars, and away from large pickup trucks and sport utility vehicles.
"We expect the second half of 2008 will be more challenging than the first half, as weak economic conditions and the consumer credit crunch continues," said Jim Farley, Ford group vice president of marketing.
Ford truck and van sales fell 39 percent to 54,565 with SUV sales diving 53 percent and F-series truck sales falling 42 percent to 40,429.
The Ford F-150 pickup truck had until recently was the top-selling vehicle in the U.S. Poor truck and SUV sales recently caused Ford to delay the launch of its redesigned F-150 pickup truck company executives hoped would drive a recovery at Ford.
Overall automobile sales are down anywhere from 14 percent to 19 percent. That represents a slight increase from the 16-year low reported in July.
