Mary T. Barra has often referred to her years of experience on the General Motors factory floor. So it was familiar terrain when the chief executive embarked this year on a tour of plants across the Midwest and South, a mission to create good will among unionized workers ahead of contract talks.

At the Lake Orion assembly plant near Detroit, she said G.M. was going to spend $300 million to prepare the plant to make a new electric vehicle, creating 400 jobs. She traveled to Spring Hill, Tenn., to announce $22 million in spending, and chatted with workers in Lansing, Mich., where G.M. had chosen to make a new sport utility vehicle.

“The success of our new trucks and S.U.V.s and crossovers is allowing us to create jobs all over the company,” she said at a pickup plant in Fort Wayne, Ind., which was tabbed for $24 million in upgrades.

The effort hasn’t engendered as much harmony as G.M. might have hoped. Negotiations that started over the summer failed to head off a walkout by 49,000 members of the United Auto Workers on Sunday night, the first against G.M. since 2007.