Production workers at the GM Flint Engine Operations plant voted against the tentative United Auto Workers contract, but all other groups in Local 659 voted in favor of the deal.
Flint's role in potential UAW strike is unknown but city has been front and center of past battles mlive.com - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from mlive.com Daily Mail and Mail on Sunday newspapers.
GM did not immediately announce additional jobs tied to the planned upgrades but said they reflect a commitment to the city and its existing workforce.
The investment will go into the Flint Assembly Plant and Flint Metal Center to prepare those sites for producing next-generation, gas-powered heavy-duty trucks.