The United Auto Workers union says nearly 4,000 members are on strike at heavy truck manufacturer Mack Trucks after voting down a tentative agreement reached a week ago. The union said 73% of its workers had voted against the proposed deal. “I’m inspired to see UAW members at Mack holding out for a better deal, and ready to stand up and walk off the job to win it,” UAW President Shawn Fain said in a statement issued Sunday on X, the social media platform formerly known as Twitter. The union said the rejected contract included an immediate 10% pay raise, and 9 percentage points of additional pay increases over the five-year life of the contract, a $3,500 signing bonus, improved vacation and holidays and no increase in insurance premiums paid by members. Stephen Roy, president of Mack Trucks, said in a statement that he was “surprised and disappointed” that the union had chosen to strike. “The UAW called our tentative agreement ‘a record contract for the heavy truck industry,’” he said in the statement. He said the company assembles all of its trucks and engines for the North American market at US plants and that it “continues to compete against products built in lower-cost countries.” His statement said the company looks forward to returning to negotiations “as soon as possible.” “We are committed to the collective bargaining process, and remain confident that we will be able to arrive at an agreement that delivers competitive wages and benefits for our employees and their families, while safeguarding our future as a competitive company and stable long-term employer,” he said. News of the work stoppage at the heavy-duty truck maker comes as the union continues to wage strikes against three biggest car manufacturers. Mack Trucks is one of the major US makers of heavy duty and medium duty trucks, with deliveries of 27,000 in 2022 and 16,000 for the first half of 2023. It is owned by Sweden’s Volvo Group, separately from the Volvo car brand, which is owned by China’s Geely. The union’s stated bargaining goals at Mack mirror many of its demands in talks with the Big Three automakers — General Motors, Ford and Stellantis, which makes cars under the Jeep, Ram, Dodge and Chrysler brands — including improved wages and health care and pension benefits. It is the first time in the union’s history that it has struck all three unionized automakers at the same time. Fain told members on Friday that the three-week long strike had already prompted the automakers to meet some key union demands, even if there was not yet an agreement. He said the progress in negotiations allowed the union to forgo plans to expand the strike to other facilities. More than 25,000 union members at five assembly plants and 38 parts distribution centers nationwide are now on strike. President Joe Biden became the first sitting president to visit a picket line when he showed up last month at a striking GM facility to voice support for strikers. But the rejection of the tentative agreement at Mack Trucks shows how difficult it may be for the union to win an agreement with GM, Ford and Stellantis that will be ratified by rank-and-file membership. Any deal reached at the three unionized automakers will need to be ratified by membership in order for the strike to end. Rejecting deals The proposed deal between Mack and UAW was reached last week just minutes before the union’s contract had been due to expire on October 1. It has become more common in recent years for rank-and-file union members to vote down tentative labor agreements reached by their union leadership. In July, 57% of FedEx pilots voted down a proposed contract reached in May, which would have provided for a 30% pay increase, as well as a 30% improvement in pension benefits. But because those pilots and other airline employees work under a different labor law, they were not allowed to immediately go on strike the way workers at Mack Trucks and most other private businesses can once their labor contracts expire. Two years ago, UAW members at John Deere voted “no” on a tentative contract negotiated by their union leadership. They subsequently voted down another tentative agreement and decided to stay on strike, before eventually accepting a third tentative agreement and returning to work after a five-week-long work stoppage. Strikes have become far more common this year. Unions are taking advantage of a strong US labor market to flex their muscles and demand better pay, benefits and work conditions for their members. The number of strikes with 100 or more strikers that have lasted a week or more has soared to 56 in the first nine months of this year, according to a database of labor actions kept by the Cornell University School of Industrial and Labor Relations. That figure, which is 65% higher from the same period last year, means there has been more than one such strike a week. And it doesn’t even include significant shorter actions, such as the three-day strike staged last week by 75,000 health care workers at Kaiser Permanente. The unions involved in that strike had previously intended to return to work after three days, but they have threatened an even longer strike in November if their demands for better pay and improved staffing are not met.