General Motors and the United Auto Workers have reached a tentative agreement, less than 48 hours after the union struck the automaker's Spring Hill Assembly plant in Tennessee where it produces popular Cadillac SUVs and various engines used in other models across its four brands, the Detroit Free Press has learned.

The UAW already has a tentative agreement that it reached with Ford Motor Co. last Wednesday. It reached a deal with Stellantis on Saturday that mirrors the one it has with Ford.

Despite marathon bargaining sessions with GM that ran into the early morning hours over the past few days, the two sides had been at a standstill, prompting the union to order the walkout at Spring Hill and ratcheting up the pressure on GM to get a tentative agreement.

No details on the agreement between GM and the UAW were known at the moment, but two sources with knowledge of the negotiations told the Detroit Free Press, part of the USA TODAY Network, over the weekend that GM had at that time offered matching financials to the Ford deal. That includes a 25% wage increase across the life of the contract, a reinstatement of the cost-of-living adjustment and the same profit-sharing formula. A vote is expected after local union leaders review the contract terms with members in the coming days.

UAW President Shawn Fain outlined the top items in the Ford contract Sunday night saying he and union negotiators "wholeheartedly" endorse it for ratification. He urged people to visit www.uaw.org/ford2023 for more details.

Pressure was on to get a deal done

The pressure was intense on GM to get a tentative agreement with the UAW, especially with the elevated strike action at Spring Hill Assembly, labor experts said after Ford and Stellantis both got deals done.

"All signs are pointing to the end game here," Peter Berg, a professor of employment relations and director of the School of Human Resources and Labor Relations at Michigan State University, told the Free Press. "Once you get one deal, it allows the other parties to look at that and say, 'OK, what’s good for us?' I think they’re probably closer than not closer at this point. We’re looking at a matter of days. When one agreement comes, it’ll be a lot easier for the others to come."

A big motivation is cost. On Tuesday, GM said the union's targeted Stand Up Strike would cost it about $200 million a week in lost production revenues going into the fourth quarter based on the plants that were down at that time. That figure did not include GM's Arlington Assembly plant in Texas where GM builds its profit-making big SUVs, which the UAW struck later that day. It also did not include strike action against Spring Hill Assembly. Stellantis has not yet released a cost figure, but labor experts estimate it would be similar to GM's cost.

"Now is the time where GM sees what the overall framework is with Ford and does it. Otherwise, they’re paying $200 million a week with the uncertainty of more plants going out," said Harley Shaiken, labor expert and professor emeritus at the University of California, Berkeley.

On the UAW side there was also pressure to wrap it up, Berg said. The union's leaders know some members bear the burden more than others given that some have been on the picket lines since Sept. 15 when the strike started at GM's Wentzville Assembly plant in Missouri, Ford's Michigan Assembly plant and Stellantis Toledo North Assembly Complex. Fain has gradually expanded the strike since then to other facilities across the Detroit Three with about 45,000 of the 150,000 autoworkers on the picket line at the strike's peak.

"That starts to wear out" for those who've been on strike living off of $500 a week strike pay, Berg said. "At some point, the solidarity of the union slips away and that’s important to keep because they all have to vote on the agreement. You don’t want to get that kind of division.”

Then there are the auto parts suppliers who are anxious and watching this closely, Berg said. Many have had to lay off hundreds of workers after the plants they supply parts to went idle due to the strike.

While strikers at Ford and Stellantis are now off the picket lines, preparing to return to work as they consider their tentative contracts for ratification, GM has the following facilities still on strike: 18 parts distribution centers, Wentzville Assembly in Missouri, Lansing Delta Township Assembly in Michigan, Arlington Assembly in Texas and Spring Hill Assembly.

This story is developing.

Contact Jamie L. LaReau: [email protected]. Follow her on Twitter @jlareauan. Read more on General Motors and sign up for our autos newsletter. Become a subscriber.