DETROIT — If they can close our plant, they can close yours, too. That’s the message from workers at three shuttered General Motors factories that didn’t get new products under the tentative contract agreement reached last week between GM and the United Auto Workers, who have been on strike against the company across the U.S. for over six weeks now.

About 2,000 employees who once worked at GM transmission plants near Baltimore and Detroit and a small-car assembly plant in Lordstown, Ohio, will repeat that message this week as 49,000 union members vote on the four-year deal.

Approval could end the walkout that has crippled GM’s production and cost the company $2 billion.

Most of the workers who lost their jobs at the three sites are scattered across the country after transferring to other GM factories.

But few are holding out hope they can torpedo the contract, which comes with an $11,000 signing bonus, pay raises and plenty of other economic goodies for the factories that are staying open.

John Sandquist Jr., who spent 25 years building cars at Lordstown near Cleveland, said he is not optimistic he will change other people’s minds, but he will vote against the pact.

“Your plant can be shut down at any time,” Sandquist said. “What the contract is lacking is the language to prevent this from happening again.”

At a meeting of factory-level union leaders in Detroit last week, Dan Morgan, bargaining chairman for the local in Lordstown, made a plea to vote the contract down, saying they should stay on strike until GM keeps the plants open.

Union spokesman Brian Rothenberg said bargainers did the best they could, getting early retirement and buyout offers for workers from the closed factories who didn’t move.

So far, a large assembly plant in Spring Hill, Tenn., narrowly voted down the contract. But locals in Toledo, Ohio, at GM’s technical center in Warren, Mich., and at a metal stamping facility in Saginaw, Mich., voted overwhelmingly in favor.

Voting wraps up on Friday, with the final tally to be released that evening. As of Tuesday, the deal was winning by more than 1,000 votes.