Sales of medium- and heavy-duty trucks climbed 9.7% last year in the U.S., closing out 2006 with a record 544,581 deliveries, Ward’s data shows.

The previous record of 521,190 units was set in 1999.

Related document: Ward's U.S. Truck Sales by Weight Class December 2006

This year’s stricter emissions regulations helped push December sales.

Combined, medium- and heavy-duty trucks registered a 13.6% surge in the final month, tallying 50,324 units and all gained in the year.

Class 8’s biggest winner in December was Volvo Truck North America Inc.’s Volvo brand, which saw sales spike 40.7% to 3,499 from year-ago’s 2,582. Volume-leader Freightliner LLC posted a 12% increase in the month, closing out 2006 with 98,603 units, up 3.9% from 2005.

Class 8, overall, saw sales climb 18.1% in December vs. year-ago, to 26,462 units, closing the year up 12.3% to 284,008 units. All but Freightliner’s Sterling brand, down 4% to 1,540 units, enjoyed growth in the month.

PACCAR Inc.’s Peterbuilt brand led Class 8 sales for the year, up 23.3% to 37,322 units. All makers and brands in the segment saw increased sales vs. 2005. Total medium-duty sales ended 2006 up 6.9% to 260,573 units.

December’s medium-duty deliveries rose 9.0% to 23,862 units, due to strong showings in Class 6, up 29.2% to 6,305 units.

Leading the month, International Truck and Engine Corp.’s sales surged 79.2% to 2,131 units, for a 33.8% segment share vs. year-ago’s 24.4%.

Combined Class 6 sales for 2006 grew 16.4% to 70,029 units, with Isuzu Motors Ltd. the biggest gainer at 80.4% to 294 units. General Motors Corp. suffered the greatest loss in the segment, down 20% for the year, with sales sliding 33% in December.

Class 7 sales rose a modest 2.3% in December and ended the year up 2.2% to 90,792 units. Nissan Diesel saw the biggest increase for the year, with sales nearly doubling to 157 units from 80 in 2005.

A 5,121-unit tally pushed Class 5’s December deliveries 8.7% ahead of year-ago, with GM’s imported models posting the largest increase, up 88% to 306 units.

Class 5 finished 2006 up 6.9% to 49,466, with International the biggest gainer in the year, up 97.2% to 785 units. Hino Motor Mfg. USA Inc.’s domestic models saw the greatest falloff, down 52.9% to 258 units.

Class 4, alone, is posting a decline in December, with sales slipping 0.6% from year-ago. Isuzu was the biggest gainer, with sales of domestic models rising 37.9% to 381 units. GM’s domestic models slipped 33.5%, to 769 units.

Class 4 ended the year 3.7% ahead of 2005, at 50,286 units. Mitsubishi Fuso led, with a 37.4% rise to 3,403 units.

December medium- and heavy-duty sales translate into a 600,000-unit seasonally adjusted annual rate, up from like-2005’s 530,000.

Class 8 inventories stood at 53 days (53,586 units) in December, up from year-ago’s 51 days (43,883 units).

Inventories of medium-duty trucks rose to 88 days (80,765 units) in December, up from prior-year’s 73 days (61,503 units).

In other news, PACCAR announces it will build a new $400 million engine plant in the southeastern U.S., without specifying an exact location. Construction is slated to begin mid-year and should be completed by 2009.

PACCAR President Tom Plimpton says the new factory will be the company’s most technically advanced, designed for “maximum flexibility to supply products and components to PACCAR facilities and customers on a global basis.”