A 2.6% uptick in December helped boost U.S. sales of medium- and heavy-duty trucks to a 9% full-year gain over 2009, according to Ward’s data.

Big-truck sales for 2010 totaled 217,702 units, compared with prior-year’s 199,686. But putting the jump in clearer perspective, 2008’s tally was 298,424.

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

Class 8 sales in December rose 5.5%, as slight declines at Daimler AG, International Truck and Engine Corp. and PACCAR Inc.’s Kenworth brand were offset by Volvo Truck North America Inc.’s 48.2% rise. Daimler’s Western Star marque also gained, as did PACCAR’s Peterbilt.

For the year, Class 8 outpaced 2009 by 13%, led by Western Star’s 65.4% jump. However, Daimler finished No.1 in volume.

Medium-duty sales in December were flat, but for the year they rose 5.4%. Class 7 in December gained 14.6% from like-2009, led by Daimler and International.

For the year, Class 7 lost 1.9% of its 2009 volume, thanks to an 86.2% decline at Daimler’s Sterling brand and a 78.8% plunge in General Motors Co. sales. Both are exiting the medium-duty market.

International retained the top volume spot in Class 7, with 15,333 deliveries.

Class 6 dropped 13.3% last month, but for the year it was the best-performing sector, soaring 32.5% from 2009 levels.

Losses at most manufacturers sunk Class 6 in December, although many posted increases for full-year 2010, including volume-leader International. Its sales jumped 29% for the year, while Ford posted the biggest hike on a percentage basis, 86.9%.

Class 5’s 51.9% rise was December’s biggest percentage-based improvement, powered by a 261.6% gain by Daimler’s Freightliner brand. Also in the black last month was volume-leader Ford, up 81.1%.

Ford again was Class 5’s No.1 volume brand in 2010, racking up 18,295 sales, a 73.3% increase over 2009.

Isuzu Motors Ltd. was the leading gainer in Class 5 in 2010, up 134.8%. Class 4 suffered the biggest loss in December and for the year, down 65% and 39.2%, respectively.

Isuzu’s imported units gained 76.8% in December, compared with like-2009. But its tally, which went from 207 units to 353, was not enough to offset losses by other high-volume manufacturers. International’s 218.5% jump in full-year Class 4 sales was overshadowed by losses at GM, Daimler and volume-leading Ford.

Class 8 closed out 2010 with a 49 days’ supply as of Dec. 31, or 21,412 units, down from 53 days in like-2009, or 21,735 units.

Medium-duty stocks also dropped, going from a 57 days’ supply at month’s end, or 23,283 units, compared with 68 days or 27,931 in December last year.