Canadian big trucks posted a 42.1% hike in May, according to Ward’s data.

The performance roughly mirrored the U.S. market, with Class 4 the lone group to record a shortfall.

Class 8 sales climbed 41.3% on gains by all manufacturers, led by Volvo Truck’s Mack brand. Its deliveries soared 118.4%, compared with like-2010.

Related document: Ward’s Canada Truck Sales by Weight Class – May 2011

Medium-duty sales posted a 43.6% increase in May, with Class 7 deliveries up 36.8% on the strength of domestically built units.

PACCAR was both the group’s biggest winner and loser in May. Its Kenworth brand saw sales skyrocket 146.2%, while the Peterbilt marque was Class 7’s lone sub-par performer with a 23.6% deficit, compared with prior-year.

Thanks to large percentage gains on small volumes, Class 6 sales rose 64.8%, with Hino and PACCAR recording increases of 131.5% and 108.3%, respectively.

Class 5’s 78.9% was the largest climb by any big-truck group. As in the U.S., Chrysler posted the segment’s most substantial gain, up 400.8%.

Class 4 sales slipped 17.2%. Although it was one of the smaller percentage losses, segment-leading Ford’s 12.5% dip accounted for most of the volume decline from year-ago.

Through May, big-truck sales in Canada totaled 13,394 units, 24.2% ahead of like-2010.