LISLE, Ill. (AP) — Navistar International Corp. says its chairman and CEO has stepped down and named an interim replacement.

The surprise announcement sent its shares up more than 7 percent in morning trading Monday.

The heavy truck and engine company said that Daniel Ustian informed the board that he is immediately retiring from his roles as chairman, president and chief executive, as well as leaving the company's board.

Lisle, Ill.-based Navistar named Lewis Campbell, the former chairman, president and CEO of Textron Inc., as its executive chairman and interim CEO.

Navistar has struggled this year amid uncertainty about whether its Class 8 engine, which is used in the largest commercial trucks, will get Environmental Protection Agency approval. Since the beginning of this year, its shares have tumbled 39 percent.