“One of the biggest issues for us is the job security,” Walter Smith, president of the local representing Pennsylvania workers, told WCAU-TV in Philadelphia. “I’ve been here for 42 years at Mack Trucks, love working at Mack Trucks. But we need to have our job security.”

The Mack Truck strike follows the decision by 46,000 General Motors workers to go on strike, a labor dispute that’s now in its fifth week and is projected to have longer-term ramifications for the auto industry and organized labor. GM is losing an estimated $450 million a week, and the strike could ripple through the economy.

The union said many issues are unresolved with Mack Truck’s management, including wages, job security and pension and health benefits. Union officials say they will be available to reconvene negotiations Oct. 21, nine days after the beginning of picketing.

In a statement, Mack Trucks President Martin Weissburg said he’s “surprised and disappointed” that the union decided to walk out “rather than to allow our employees to keep building trucks and engines while the parties continued to negotiate.”

“We have no plans to close any U.S. manufacturing,” he added. “On the contrary, we’ve invested more than $400 million in our plants and logistics network over the last 10 years, and since 2015 have insourced work that has created more than 500 jobs in our U.S. factories. We have significant new investments in both facilities and products on the way.

“We are committed to the collective bargaining process, and remain confident that we will be able to arrive at an agreement that provides a competitive wage and benefit package for our employees and families, and helps to ensure the company’s competitiveness.”

In 1984, some 9,200 Mack Truck workers went on strike for nine days, closing the manufacturer’s U.S. plants before a tentative agreement was reached.