NEW YORK (CNN/Money) - Detroit's Big Three automakers said U.S. sales fell in March, with Ford Motor Co. reporting an 11.7 percent drop, General Motors Corp. posting a 2 percent drop and DaimlerChrysler seeing a 4 percent decline. All blamed declines in fleet sales to rental companies.

Ford's sales fell across a wide range of models and brands, with an 11.2 percent decline in car sales and a 12 percent drop in sales of light trucks, which include vans as well as the pickups and sport/utility vehicles that are a key to the company's profitability. Overall it sold 328,385 vehicles in the month, and only its high-end Jaguar and Land Rover brands posted year-to-year sales gains in the period.

Shares of Ford (F: down $0.35 to $15.38, Research, Estimates), which were already lower before the report, lost more ground after the noon ET sales data release.

Once again fleet sales to businesses, especially rental car companies, posted an even sharper drop than retail sales directly to customers. Ford said fleet sales were down 21 percent. The company did not disclose the decline in retail sales.

GM, the world's largest automaker, said March sales declined 2 percent from a year earlier to 419,410 cars and trucks. Car sales alone fell 12 percent, largely because of a 34 percent decrease in fleet volume, the company said. Truck sales increased 8 percent from a year ago.

GM also said retail sales, that is sales to individuals, increased 6 percent from a year earlier thanks to a double-digit increase in retail truck sales.

GM (GM: up $0.22 to $59.92, Research, Estimates) shares were down 1 percent in Tuesday afternoon trading immediately following the report.

"Our retail sales were strong again in March and we exceeded our expectations despite another substantial reduction in daily rental fleet volume," Bill Lovejoy, GM's group vice president of North American vehicle sales said in a statement. "We continue to exceed our year ago retail levels, our share continues to stabilize and our inventories remain lean."

GM's mid-size utility trucks led sales last month, increasing 52 percent from a year ago, and was the second best month in company history, GM said.

The Chrysler arm of DaimlerChrysler AG (DCX: down $0.23 to $44.94, Research, Estimates) U.S. sales fell 4 percent in March. The company sold 58,070 cars, down 1 percent from a year ago, and 159,088 trucks, a 5 percent decline.

Sales of its key Dodge Ram pickup increased 8 percent, while Chrysler PT Cruiser sales rose 11 percent.

Ford has been losing market share not only to overseas automakers but also to GM. Ford executives warned late last month that it has been forced to keep incentives and other marketing costs higher than budgeted in order to support sales.

"About the only thing I could say is I have expected and would expect our year-to-year decline to be more than the industry," George Pipas, Ford's U.S. sales analysis manager, told analysts during a conference call Monday. He cited the sharp decline in fleet sales as a big part of that drop, but declined to estimate how much Ford's sales performance lagged the rest of the industry.