Sales of medium- and heavy-duty trucks posted a 5.8% increase in June on strong performances by Classes 4, 5 and 6.

Class 6 deliveries led all groups, jumping 58.9% last month due to triple-digit percentage increases by Ford, Peterbilt and class-leader Daimler.

Class 8 was the only declining group in June, down 5.4% as about half of its manufacturers posted declines.

International’s 23.2% drop was the steepest, with Volvo Truck’s namesake brand close behind, down 22.5%.

Freightliner again made Daimler the leading Class 8 manufacturer in June, with sales climbing 20.2% compared with like-2012. Daimler sold 6,143 units in total last month.

The positive results in Classes 4, 5 and 6 pushed medium-duty sales up 21.1% from June 2012.

Bucking the medium-duty trend, Class 7 deliveries inched up just 0.6%. Hino’s 43.4% retreat and International’s 9.6% drop couldn’t offset growth elsewhere, including at PACCAR, whose U.S. Class 7 sales improved 30.0% last month.

In Class 6, Ford led all gaining brands, up a whopping 462.5% to 1,040 units, giving it a market share of 22.2% compared with 6.3% year-ago. Peterbilt was just behind Ford, with deliveries soaring 453.8%, albeit on much smaller volume of just 32 units.

Freightliner’s 155.7% spike made it the Class-6 market-share leader, a position held last year by International, whose group sales declined 20.5% last month.

Class 5’s 13.3% increase was driven by the continued dominance of Ford, whose sales climbed 28.9% from like-2012. Ford’s slice of Class 5 surged to 72.9% last month from 64.1% year-ago.

International’s woes carried over to Class 5, where it lost 41.1% of its year-ago volume.

Chrysler’s Class-5 sales fell 27.9%.

The second-best performing big-truck group in June in the U.S. was Class 4, up 27.0%, and again Ford was the reason. The Blue Oval brand’s 385 deliveries, compared with two year-ago, lifted the segment, which saw declines by each of its remaining three brands.

International’s 97.5% collapse was the biggest, on sales of just two units compared with 82 in June 2012.

At the year’s halfway point, sales of medium- and heavy-duty trucks in the U.S. were running 4.1% behind year-ago, WardsAuto data shows.

As was the case in May, days’ supply and units in inventory both fell.

Class 8 days’ supply ended June at 56, down from 67 year-ago, while stock fell to 34,503 units from 43,365.

Medium-duty days’ supply was 67, compared with 87 in late June 2012. Medium-duty units in inventory slipped to 38,831 from 41,399.

In other big-truck news, Navistar International names former General Motors exec Walter Borst chief financial officer. He succeeds Andrew Cederoth, who resigned at the end of June from the position he’d held since 2009, Reuters reports. Navistar CEO Troy Clarke also is a former GM executive.

Meanwhile, Navistar Defense’s West Point, MS, plant idled production July 5. Navistar blames the federal government sequester, which reduced U.S. military spending, for slicing orders for the armored tow trucks and ambulances assembled at the plant. Mississippi’s ClarionLedger.com reports the plant’s 80 workers were notified in late June of the idling.

Separately, the Kenworth T800 now is available for rent, as part of parent PACCAR’s new PacLease program. FleetOwner.com says the T800s, which run on liquefied natural gas, will be available for leasing July 15 at a Kenworth dealership in Salt Lake City, UT, and a PacLease franchise in West Valley City, UT. The trucks can be rented on a first-come, first-serve basis, and with 48 hours’ notice transported to Kenworth or PacLease locations in three other western states: Idaho, Nevada and Oregon. These states have LNG fueling stations recently constructed by PACCAR partner Blu LNG. Initially available are tandem-axle day-cab T800s, with heavy-haul and sleeper units due in late July.

cschweinsberg@wardsauto.com