U.S. big-truck sales continued their winning streak with 18,742 deliveries in July, a 12.3% sales jump compared with like-2009, according to Ward’s data.

Related document: Ward’s U.S. Truck Sales by Weight Class – July 2010

All groups except Classes 4 and 7 saw sales gains, with Class 5 posting the biggest increase, 65.2%, on standout performances by Chrysler Group LLC (274.8%), Isuzu Motors Ltd. (179.8%), Daimler AG’s Mitsubishi Fuso (173.7%), and Ford Motor Co. (113.8%).

Class 5’s biggest loser was Daimler’s Sterling-brand domestic units, down 98.4%. A 63.2% drop in Class 4 sales held medium-duty trucks to a 2.9% uptick in July vs. like-2009.

Class 4 was sunk by an 81.9% drop at No.2 best-seller Ford and freefalls of 87.6% and 94%, respectively, by General Motors Co.’s domestic and imported units.

Class 6 sales rose 17.6% in July, with big gains at Ford, up a hefty 211.0%, and a 148.2% jump by Daimler’s Freightliner-brand. Those hikes offset a 32.2% loss at volume-leading International Truck and Engine Corp.

But it was Daimler’s Sterling that lost the most volume in Class 6 on a percentage basis, down 96.3% in July.

Class 7 deliveries slipped 4.6% despite a 195.3% surge by imported-units – almost exclusively due to UD Trucks 258.9% increase. The imports’ performance was offset by a 5.5% decline in domestic-unit sales. GM and Sterling lost 97.9% and 97.8% of their year-ago volume, respectively, last month vs. like-2009.

Class 8 again shone brightly, with a 23% increase in July. Volvo Truck North America Inc.’s namesake brand saw its sales soar 114.3% from year-ago, while Daimler’s Sterling recorded the steepest decline at 98.9%.

Through July, U.S. big-truck sales were tracking 10.6% ahead of year-ago, with 122,758 deliveries.

Inventories of Class 8 and medium-duty trucks fell in both units and days’ supply in July.

Class 8 saw a 56 days’ supply (20,010 units) from 78 days (22,485) year-ago. Medium-duty days’ supply shrunk more sharply, down to 65 days (22,118) from 95 (31,264) at the end of July 2009.

In other big truck news, the American Truck Dealers unit of the National Automobile Dealers Assn. is appealing to President Obama for a stimulus program to spur sales of new big trucks. ATD says low 2009 sales and new emissions standards for 2010 have added as much as $13,000 to the price of a new truck, causing owners to delay replacement.

ATD is pleading with the Obama Admin. and Congress to grant a 10% investment tax credit for Class 8 trucks whose engines meet 2010 emissions regulations. A voucher of $6,000-$8,000 is being requested for the purchase of Class 6 and 7 trucks, “totaling no more than $3 billion,” ATD says.