Shares of Navistar International Corp. (NAV - Get Report) fell Friday after the the truck and bus manufacturer missed Wall Street's first-quarter earnings expectations, but beat revenue forecasts.

The Lisle, Illinois-based company reported first-quarter earnings of 11 cents a share, up from a year-ago loss of 74 cents, but short of analysts' expectation of 15 cents a share. Sales increased 28% to $2.4 billion, while Wall Street was looking for $2.2 billion in revenue. The revenue boost was driven by a 50% increase in the company's core volumes, which represent its sales of Class 6-8 trucks and buses in the United States and Canada.
 
Shares lost 2.8% to $38.20 in recent action.

Truck segment net sales increased 44% to $1.8 billion, the company said, primarily due to higher volumes in the company's core markets and an increase in Mexico truck volumes. This was partially offset by lower defense sales due to the sale of a majority interest in Navistar Defense during the quarter. The parts segment net sales decreased 4% to $548 million, primarily due to the adoption of a new revenue recognition standard and to lower Blue Diamond Parts (BDP) sales, which were partially offset by higher sales in North America.

Looking ahead, Navistar forecast industry retail deliveries of Class 6-8 trucks and buses in the United States and Canada to range from 395,000 to 425,000 units, with Class 8 retail deliveries of 265,000 to 295,000 units. Revenues are expected to be between $10.75 billion and $11.25 billion, while analysts are forecasting $10.74 billion.

"We had our best first quarter since 2010 as customer acceptance of our new products translated to extended gains in our Core market share," Troy A. Clarke, chairman, president and CEO, said in a statement. "In addition to our ongoing growth in Class 8, our medium-duty market share grew by six points during the quarter, the largest year-over-year medium share gain in the industry."