LOWER MACUNGIE TOWNSHIP, Penn. — More than 3,600 Mack Truck workers in five cities went on strike Oct. 13. “We had to show them we were serious and united about turning down all their concession demands,” Walt Smith, president of United Auto Workers Local 677, told this Militant worker-correspondent at the union hall the next day.

Almost 1,500 workers gathered here in a spirited rally to start the picketing, waving signs and wearing red union T-shirts outside this massive cab and vehicle assembly plant, the largest of Mack’s plants, with some 2,000 workers.

In addition to this plant, Mack — which was bought by Swedish Volvo in 2000 — has a sizable powertrain factory in Hagerstown, Maryland, and other facilities on strike in Middletown, Baltimore, and Jacksonville, Florida.

According to the UAW, union representatives could not reach agreement with the company over wage increases, “job security,” work schedules, seniority, pensions, health care coverage, subcontracting and the use of temporary workers.

Smith said that in addition to the temps, the last contract put in place multiple tiers among full-time workers, with new employees starting at about $20 an hour, but not reaching full pay of $26 for six years.

This is the first strike by the union against Mack in 35 years. Along with the monthlong strike at General Motors and Aramark, it’s the third major UAW strike currently taking place in the U.S. There is an uptick in labor actions today as workers seek to make gains against relentless concession demands from the bosses.

Coupled with Volvo’s own truck division, Mack accounts for 17% of the U.S. and Canadian heavy-duty truck market.

Volvo boasts that unlike its main U.S. competitors, including Navistar International Corp. and Daimler Trucks North America — both of which import many trucks from their plants in Mexico — Mack and Volvo manufacture all their trucks in the U.S.

That’s worked out well for Volvo, which over the last several years has made record profits off truck sales. Sales surged so fast that Mack Truck couldn’t keep up with orders and is still working through the backlog.

But the big truck market is softening today, as manufacturing and related trucking have shown signs of cooling off. Mack bosses had said before the strike they were considering a cutback in production here sometime in the fall.

“The last four years we have helped Mack Truck make significant profit through our work,” Doug Irvine, president of UAW Local 2301 in Baltimore and head of the UAW’s Mack Truck Council, told the press. “All we are asking is that the company treat us with the dignity and respect we deserve.”

“We have no plans to close any U.S. manufacturing,” Mack President Martin Weissburg said in a press release.

But the unionists know better than to trust what the bosses say. “At one point they set up a plant in South Carolina they thought was going to be nonunion,” Dan Frey, who has worked 47 years at Mack, told the Militant. “But we went down and organized that plant. After Volvo bought Mack Truck they closed that plant down and moved production back here. We’re not going to let them try that again.”

The company wants to make workers pay higher insurance premiums, UAW Local 171 Executive Board member Mike Lindewurth told two Militant worker correspondents who visited Hagerstown Oct. 15.

As many as 15% of the workers there are temps who get paid less, just like at General Motors, Lindewurth said, and Mack Truck bosses want to increase that number. “We don’t like it that someone we are working shoulder-to-shoulder with is making less,” he said. “It’s unfair.”

“We all do the same jobs, we should get the same pay,” Local 171 President David Fowler added.

In addition the company wants to stop paying overtime until workers hit 40 hours in a week.

“We’re out here picketing from top to bottom,” picket captain Chawn Rosenberry said, “to get everybody a fair deal.”

Company officials told the union they wouldn’t be ready to reopen negotiations until Oct. 21.

Sarah Ulman from Washington, D.C., contributed to this article.