DETROIT — Beyond the cultural impact of Mary Barra’s breakthrough as the first female CEO of a major automaker, her ascension is an encouraging signal to General Motors’ employees who have dedicated their careers to making better, more exciting cars and trucks.

Not since Bob Stempel was CEO in the early 1990s has the nation’s largest automaker been led by an auto engineer, let alone one who worked her way up from the factory floor.

It’s OK to call Barra a “car gal.” She has been responsible for such recent vehicles as the new Corvette to the 2014 Chevrolet Silverado and GMC Sierra to the new Cadillac CTS as head of global product development.

In a company where the leaders have normally come from the world of finance, that is just as symbolic as Barra’s gender.

“Mary was not picked because of her gender,” said CEO Dan Akerson, who will retire next month. “Mary is one of the most gifted executives I’ve met in my career. She was picked for her talent.”

The promotion makes the 51-year-old Michigan native one of the most powerful women in the corporate world. Given that women make 52 percent of car buying decisions in the U.S., that could be an advantage, but the market will decide.

Akerson’s departure comes sooner than he planned, but he learned two months ago that his wife, Karin, is battling advanced-stage cancer.

“It was not my intention for my days at General Motors to end this way, but when you think about life’s priorities, my family and my wife rank No. 1,” Akerson said on a conference call.

The moves — there was a shuffling of the entire top executive team — lay the foundation of GM’s life beyond U.S. government ownership.

“I truly believe this is the best auto company on the planet — and it’s because of the men and women that work at General Motors across the globe,” Barra told employees Tuesday morning.

Barra was believed to be one of four potential successors for Akerson. Others were GM North America President Mark Reuss, GM Vice Chairman Steve Girsky and GM Chief Financial Officer Daniel Ammann.

Reuss will succeed Barra as head of global product development. Ammann was named president, and Girsky will leave the company next April, but will stay on the board of directors.

The automaker is splitting the post of chairman and CEO, assigning the chairmanship to GM director Theodore (Tim) Solso, former CEO of engine manufacturer Cummins.

Investors weren’t fazed by the unexpected timing of the moves, as GM stock, which hit an all-time high Monday, fell 50 cents to close at $40.40.

“It’s a great example of a well-chosen leader who happens to be a woman and is not there for any ornamental or political reason,” said Jeffrey Sonnenfeld of the Yale School of Management. “She knows the business as well, or better, than any guy.”

In her current job, Barra reduced the number of GM engineers in charge of each product development program from three to one.

During an earlier stint as head of GM’s human resources organization, she relaxed GM’s dress code to reflect the realities of the 21st century workplace, but with standards of propriety maintained.

As recently as September, Akerson dropped a hint that one of the Detroit Three would one day have a female CEO.

Reuss said in an interview that Barra employed a “very collaborative, empowering” leadership style and that he has a close relationship with his new boss. When asked whether he wanted the job, he demurred.

“That’s not why I’m here, frankly,” Reuss said. “I’m here to make the company work and if the board deems that this is where I’m going to add the most value to the company, all I really want to do is contribute, CEO or non-CEO. I’m an engineer and I love cars, and I get to do that. For me, that’s pretty good.”

The announcement came a day after the U.S. Treasury sold its final shares of GM stock.

Akerson signaled that GM would give raises to its top executives, which the company could not do without government permission until Monday. His exit package and Barra’s compensation details were not immediately available.

Barra joined GM in 1980 as a co-op student at General Motors Institute. Her first car was a red Camaro convertible from the late 1960s.

Her father was a tool-and-die maker.

Akerson appointed Barra as the company’s product development leader in 2011.

Since then, GM has introduced the Corvette Stingray, three new Cadillac models, and redesigned its full-size pickups. Some of those vehicles were well under way when she became product chief.