Sales of medium- and heavy-duty trucks fell 30.8 percent in March from a year earlier, to 28,777 units.
Sales of large trucks continued to decline, with Class 7 vehicles taking the biggest hit in sales, dropping 40.5 percent to 4,524 units. Sales of Class 8 trucks tumbled to 10,419 vehicles, down 35.2 percent.
Sales of Class 5 and 6 trucks declined by single-digit percentages in March. Class 5s dropped 9.9 percent to 3,618 vehicles, and Class 6 sales fell 6.3 percent to 4,757 units.
Class 4 truck sales followed the trend, plummeting 38.1 percent to 5,459 units.
Ford Motor Co. led the pack in March truck sales with 6,633 units, down 32.9 percent. International finished second with sales of 6,081 large trucks. International's sales decline of 6.1 percent was the smallest drop of any manufacturer.
For the first quarter, sales in classes 4 through 8 fell 30.2 percent from the year-earlier period to 80,363 trucks.