NEW YORK — Preliminary North American truck orders in April show that class 8 demand is modestly better than expected, while medium-duty is on an incline, reports the transportation division at analyst firm Bear Stearns.

Class 8 orders came in at 18,900 (versus the firm’s 16k-18k forecast), up 20 percent from March 2008.

“Quoting activity appears to be strong, though fleets increasingly are asking for (and, we believe, getting) ’09 slots,” Bear Stearns reports to investors.

Meanwhile, class 5-7 orders for April were 14,300 (up 40 percent year-to-year in March). Arguably, class 5-7 orders are a “purer” measure of economically-derived demand, notes the firm.

The current class 8 sales figures are sending mixed singles, according to Bear Stearns.

Despite the slight improvement, there’s little indication the industry has begun its rebound just yet. “We continue to believe diesel prices have soared past the high end of many carriers’ fuel surcharge indexes, accelerating pressure on carrier profitability and likely weighing on orders for at least the next several months.”

Further improvement in class 8 orders is expected in the back half of 2008, but “not due to a back-half macro recovery, but rather into stabilizing freight fundamentals and ahead of the next emissions deadline.”