The company said on Wednesday that it has reached a $1 billion agreement to acquire a majority stake in Cadillac and Chrysler, bringing total investment in the two companies to $4.9 billion.
GM said it would buy a controlling stake in both companies, which make trucks.
The deal includes the purchase of a 50 percent interest in the trucking company, GMA.
The other 30 percent interest will be owned by Cadillac and the remaining 10 percent by Chrysler.
The two companies have been trying to get a deal done for years, with the two firms making a deal last year that allowed them to jointly explore options for a merger, a deal that never materialized.
GM had been exploring possible merger with Chrysler since 2007.
GMA was acquired by GM in 2010, but was rebranded in 2017.GM said it expects to make the deal final in the second quarter of 2020.
GM is now in its third quarter.