Sales of medium- and heavy-duty trucks posted a 16.8% rise in December, lifting full-year 2013 results to their best performance in six years.

Big truck makers sold 351,737 units for the year, a 1.7% increase over 2012 and the highest level since 2007, when deliveries totaled 371,093,WardsAuto data shows.

Daimler retained its position as the volume and market-share leader in Class 8 for December as sales rose 27.4%, resulting in a share of 35.9% in 2013, up from 31.8% in 2012.

International’s Class 8 sales slid 14.0% in December and were down 23.7% for full-2013 as it struggled to redesign their engines using a different emissions strategy. The only other Class 8 manufacturer that saw December sales fall from year-ago was PACCAR’s Peterbilt brand, down 5.0%.

Medium-duty deliveries rose 21.8% last month and 10.4% for the year as all classes enjoyed year-over-year increases.

Class 7 sales climbed 14.0% in December from like-2012 and were up 1.4% for the full year, with Daimler strengthening its lead as the group’s top seller with nearly 50% of the market.

Daimler’s sales surged 19.2% for the year to 23,032 units, compared with International, down 16.0% to 11,587 units as their share dropped to 24.4% from 29.4% in 2012.

Both International and Ford saw volume underperform from prior-year. Ford was the biggest Class 7 loser, with December deliveries plunging 24.4%.

Class 6 sales rose 30.3% in December and were up 18.8% for 2013. Ford led with a gain of 106.6% while its full-year results were up 212.3%. Daimler was up 21.5% for the month and had a 41.0% gain for the year, overtaking International as the volume leader with 18,900 deliveries in 2013.

December Class 5 sales posted a solid gain of 16.2% as triple-digit increases by Daimler’s Freightliner division (+442%) and Hino (+175.1) led the segment and more than offset losses by PACCAR’s Kenworth group (-48.0%).For the year, Ford deliveries were up a modest 10.0% to 39,302 units as it remained the share leader with 65.5% of the segment. Chrysler maintained its hold on second place in Class 5, up 5.8% to 10,901.

Class 4 enjoyed the largest increase of any medium-duty group, up 61.6% for December and 26.3% for the year.

Class 8 closed out December with a 38-days’ supply, or 30,194 units in stock, down from 50 days and 34,959 in 2012.

Days’ supply of medium-duty trucks slipped to 62 units from 68 in like-2012, but inventory rose to 40,361 from 36,047.

FTR has released preliminary data showing December Class 8 truck net orders surged to 31,506 units, a significant jump of 50% from the previous month, and the first month orders have been above 30,000 since April 2011.  2013 is the highest December total in eight years with a 51% year-over-year improvement. December order activity boosted the annualized rate for the past 6-month period to 269,000 units. Preliminary order numbers are for all major North American OEMs.

PACCAR Inc. announced that its Board of directors has elected Ronald E. Armstrong as CEO and Mark C. Pigott as executive chairman of the board of directors, effective April 27, 2014. Armstrong also was elected a member of the Board of Directors, effective on the same date. Armstrong currently is president of PACCAR and succeeds Pigott who has served as the company’s CEO and chairman since 1997.