Sales of medium- and heavy-duty trucks rose 32.3% in the U.S. in July to 28,904, an increase fueled by big gains in Classes 5, 6 and 8.

Class 4 was the only weak spot, with deliveries falling 24.7% to 1,057. Imported units from volume-leader Isuzu jumped 36.7% to 588, but it wasn’t enough to offset declines from others in the segment, including Daimler and Ford, both of which posted double-digit losses.

International, a small-volume player in Class 4, saw deliveries plunge 40.1% to 52 units, while domestically produced Isuzu trucks climbed 66.7% to 120.

In Class 5, deliveries soared 37.8% to 4,083, with Freightliner sales surging 737.8% to 116. But most of the growth was due to Ford, which delivered 2,578 units in the month for a 63.5% year-over-year increase.

PACCAR, which sells the Peterbilt and Kenworth brands, saw sales jump 333.3%, albeit on only eight units.

Class 6 sales grew 34.2% to 3,242, largely due to volume leaders Daimler and International, which posted gains of 57.3% and 8.4%, respectively. Ford also recorded a solid month with a 44.0% jump to 614 units.

Hino deliveries rose 124.5% to 431, while PACCAR’s sales tumbled 37.2% to 62. UD Trucks posted a 42.5% gain on 25 units.

Class 7 deliveries jumped 25.5% to 12,483, thanks to a big gain by Daimler’s Freightliner marque, which posted a 58.5% year-over-year increase to 1,851.

PACCAR’s overall sales were up 57.0%, with Kenworth and Peterbilt posting gains of 69.1% and 50.4%, respectively.

On a percentage basis, Hino paced Class 7 with 190.1% surge to 158, while International saw a 5.1% decline, despite delivering 1,124 units.

Ford posted a 5.4% uptick vs. year-ago, while UD Trucks saw sales plummet 88.6% on just four units.

Heavy-duty truck sales were strong in July, with Class 8 soaring 38.1% to 16,421

Volvo sales were up 43.2% to 3,274, with Volvo and Mack truck posting gains of 16.0% and 77.1%, respectively.

Kenworth and Peterbilt saw increases of 32.3% and 9.2%, respectively, contributing to an overall PACCAR gain of 18.9% to 4,328.

International also helped propel Class 8 sales with a 19.3% increase on year-ago to 3,260, while Daimler led the class on a volume basis, up 72.0% to 5,558.

Big-truck stocks rose in July. Class 8 had a 62 days’ supply at the end of the month (42,607), up from year-ago’s 56 (27,673). Medium-duty days’ supply climbed to 77 (39,849) from 73 (30,395).

bpope@wardsauto.com