ALLENTOWN, Pa. -- Ralph E. Reins will resign as chairman, president and chief executive officer of Mack Trucks Inc., the chairman of the company's distributors council confirmed late yesterday.

Mr. Reins, 50, has accepted a position as head of the automotive group at United Technologies Corp. of Hartford, Conn., said Bob Nuss, owner of Rochester Mack in Rochester, Minn., and chairman of the council that includes 200 Mack dealers.

Mr. Reins will be replaced by an executive from Renault Vehicules Industriels, which on Oct. 5 completed its $107 million buyout of the 55 percent of Mack stock that it had not previously owned, Mr. Nuss said.

A leading candidate is Pierre Lecoq, who served as director of quality for the French-owned RVI before becoming vice HTC president of engineering at Mack in December 1989, informed sources said.

Mack has a large engine and transmission plant in Hagerstown.