Canadian big-truck sales climbed 25.1% in August, compared with year-ago, for their fifth consecutive monthly increase.

However, as in July, only Classes 5 and 8 posted gains.

Related document: Ward’s Canada Truck Sales by Weight Class – Aug. 2010

Credit goes to all but Daimler AG’s Sterling, down 97.4%, for Class 8’s impressive 92.4% surge. Most manufacturers in the group saw large percentage increases on volumes greater than 100 units, including Daimler’s Freightliner, whose deliveries jumped 207.5% ahead of like-2009.

Subpar sales performance for all but Class 5 saw medium-duty trucks’ monthly result slide 34.7% from prior year.

Class 7’s 65.8% tumble in deliveries was the sector’s most severe decline, due largely to volume-leading International Truck and Engine Corp.’s 87.3% falloff, to 44 units from 362 year-ago.

However, General Motors Co.’s 94.5% sales plunge to just one unit, compared with prior-year’s 19, was Class 7’s largest drop percentage wise. Freightliner was the leading gainer, up 340.7% with 55 units sold.

Class 6 deliveries slid 40.1%. Increases of 316.7% at Paccar Inc. and 281.9% at Daimler could not offset Ford Motor Co.’s 94.2% plunge or volume-leader International’s 56.1% loss.

Sales of imported units from Isuzu Motors Ltd. and Daimler’s Mitsubishi Fuso drove Class 5’s 13.2% rise. Isuzu’s 23 units, vs. three year-ago, were good for a 698.6% increase, while Mitsubishi Fuso added two units to like-2009’s 11, for a 23.1% gain.

Class 5 also saw domestic units rise in August, with Chrysler Group LLC deliveries climbing 81.6% and Hino Motor Mfg. USA Inc. up 113.8%.

Class 4 sales slipped 1.3% from year-ago resulting from a 38.4% drop in imported units. Sterling’s imported models posted the largest loss in the group, down 88.4% on just one sale, compared with nine year-ago.

Ford was Class 4’s volume-leader, with a 59.7% hike on sales of 69 units, compared with prior-year’s 45. That gain offset sales losses on other domestically built models, including those from Daimler and Hino.

Through August, sales of 17,836 medium- and heavy-duty trucks in Canada were 14.8% ahead of 2009’s 15,536.