U.S. sales of medium- and heavy-duty trucks in July saw their largest drop in almost seven years, Ward's Auto reports, and it was a similar story for sales in Canada.

Class 8 sales were the driver in both cases. In the United States, Class 8 sales fell a whopping 39.8% compared with sales in July 2015. International, Freightliner and Volvo had the biggest year-over-year sales losses for the class, dropping 56.7%, 46.1% and 41.2%, respectively. In Canada, Class 8 sales were down by less but still significantly: sales fell 32.0% vs. July 2015.

Sales in Class 7 were a rosier picture. Those were down 15.2% in the U.S. and actually were up a modest 2.1% in Canada compared with sales a year ago, according to Ward's Auto. Freightliner was the top U.S. seller (up 41.9%) for Class 7 trucks but had one of the sharpest losses in Canada (down 40.9%), while Peterbilt's Canadian sales pitched down 68.4% for the biggest drop.

For the United States, Class 6 "was the best performing group," and sales grew 11.3% from a year ago, Ward's Auto finds. Chalk that up to gains by Ford (up 59.3%) and Freightliner (up 13.5%), but Peterbilt sales also saw gains — 7.4% — compared with July 2015. Class 6 Canadian sales fared quite poorly last month compared with July 2015, however, falling by more than half.

Class 5 sales in the United States were about break-even last month vs. July 2015, down by only 0.3% overall, reports Ward's Auto, but U.S. Class 4 sales fell by 16.7% year-over-year. In Canada, Classes 5 and 4 dropped off by 9.6% and 22.0%, respectively.

The medium-duty classes were another mixed bag in the U.S. vs. its northern neighbor: for instance, FCA's Class 5 sales in July "soared" by 56.8% in the United States but fell 11.4% in Canada compared with July 2015 sales. Or Class 4 sales punished Mitsubishi-Fuso most, with the OEM posting declines of 71.0% for the month in the U.S. and 85.7% in Canada compared with July 2015 sales.

Click here for more on U.S. truck sales for the month or here on Canadian truck sales from Ward's Auto.