General Motors Corp. confirms plans to eliminate a production shift at its Detroit/Hamtramck, MI, assembly plant due to sluggish sales.

The plant builds the fullsize Cadillac DTS and Buick Lucerne luxury sedans. Sales of the DTS are down 14.4% this year, while Lucerne deliveries are off 15.3%, according to Ward’s data.

The decision affects 767 hourly workers and moves the plant to a single shift. Layoffs begin Dec.14, and the single-shift arrangement commences Jan. 2, following the annual holiday shutdown.

The news comes roughly seven days after the United Auto Workers union ratified a new collective-bargaining agreement with GM that makes unprecedented concessions on behalf of the union in return for investment commitments in the U.S.