DETROIT and LISLE, IL -- General Motors Co. (GM) and Navistar announced Wednesday they have reached a long-term agreement to develop and assemble future medium-duty, conventional cab Class 4/5 commercial vehicles. According to a news release, the alliance allows Navistar to strengthen its product lineup and GM to expand its Chevrolet commercial truck portfolio. The future products will be jointly developed using Navistar's expertise in rolling chassis configurations and manufacturing capabilities, and GM's commercial components and engines. The vehicles are slated for production in 2018. GM offered medium-duty trucks for decades before getting out of the business in 2009 in the midst of its bankruptcy reorganization and the recession. That decision followed the death of a deal for Navistar to buy GM's medium-duty business.