The New York-based analyst said new truck builds in June dropped 11.5% vs. the same period last year, the month after production increased 15.6% year-to-year.

Bear Stearns said the June decrease was the first since strong pre-buying started last spring in anticipation of new EPA-driven diesel engine regulations taking effect in 2007.

According to Bear Stearns, Navistar International posted a 33.5% drop in June vs. the same period a year ago, while DaimlerChrysler’s trucking unit fell off by 16.9% and Paccar production declined 12.3%.

While the analyst blames shortages in wheels and disc brakes for part of the downturn, it does not expect new orders to increase production in September or October.

"Class 8 monthly net new orders will go lower and stay down longer, than what’s reflected in general market expectations," Bear Stearns said. "We think the market will be even more disappointed when Class 8 orders don’t rebound later this year."

Bear Stearns said it expects orders to average between 10,000 to 15,000 a month for the next 18 months, down from a 30,000 unit/month average through the first six months of this year.