Unionized workers at Goodyear Tire & Rubber Co. overwhelmingly approved a new four-year deal, a contract that covers about 950 employees at the Town of Tonawanda plant.

Workers at the last of six Goodyear plants to cast ballots, in Alabama, finished voting Thursday. The United Steelworkers of America said members across the six plants approved the deal by a 3-to-1 margin.

Members of Steelworkers Local 135 who work at Goodyear Dunlop Tires North America on Sheridan Drive voted on the tentative deal earlier this month. In addition to Tonawanda and Alabama, the other Goodyear plants involved are in Kansas, North Carolina, Virginia and Ohio. The newly ratified deal covers about 8,000 workers.

Thomas O’Shei, president of Local 135, said each of the six locals approved the deal by at least a 3-to-1 margin. He declined to be more specific about the Tonawanda results, as part of an agreement among the six local presidents regarding the plants’ individual vote tallies.

O’Shei said the tentative deal had exceptionally strong support among union leadership. “It’s the first contract that was ever unanimously approved by the USW Goodyear Policy Committee,” he said.

The approved contract calls for a minimum staffing level of 845 employees at the Tonawanda site, O’Shei said.

The deal calls for keeping all six plants open during the life of the contract, which runs to July 2017.

“We also negotiated a commitment from Goodyear to invest in our North American facilities so that future generations can look forward to continuing the tradition of manufacturing in these communities,” said Tom Conway, a Steelworkers official, in a statement.

Ohio-based Goodyear has committed to investing at least $700 million in the six plants. The deal allows Goodyear to offer 150 employee buyouts at the Alabama plant, plus 400 more buyouts at the other facilities.

Goodyear officials plan to discuss the contract in a conference call Tuesday.

The Sheridan Drive plant employs about 1,150, producing consumer, commercial truck and motorcycle tires.