North American Class 8 net orders topped 38,100 units in April, according to data tracked by ACT Research Co. , up more than 31% from the level set in March and representing a 157% year-over-year increase as well.

Actual Class 8 sales also soared in April, growing 35.9% in the U.S. over last April and 13.7% in Canada, according to WardsAuto.com.

According to Kenny Vieth, ACT’s president and senior analyst, the order level is the strongest since March 2006, resulting in a Class 8 order backlog of over 126,000 units, a 55-month high.

“Positively, Class 8 orders continue to be placed close-in. Of April’s orders, 70% were
scheduled for build by the end of the third quarter this year,” according to Vieth. “Needless to say, open build slots remaining in 2011 are filling rapidly.”

He also pointed out that at current order fill rates, the 2011 build schedule could be completely filled by sometime in July.

“As has been the case throughout 2011, the industry’s challenge is ramping up production,” Vieth stressed. “The industry’s ability to build trucks, rather than demand for trucks will be the constraining factor on Class 8 production this year.”