The heart of America’s favorite truck comes from across the border. Ford’s Detroit-area manufacturing is split between the U.S. and nearby Canada. Every 5.0-liter V8 powering a Ford F-150 or Mustang rolls out of Windsor, Ontario. Ford’s Super Duty engines too. And now, the automaker is scrambling to haul every last engine across the Detroit River before tariffs hit.

It’s a race against time. Ford doesn’t keep inventory—it builds on demand. Components bounce between Canada, the U.S., and Mexico to be finished, so a 25% tariff on each crossing could break the entire supply chain for Ford and others.

How bad could it get? One union leader says if this tariff goes into effect, it would shut down Detroit in two weeks.

Ford’s Canada engine push is a race against time

Ford is leasing trucks and warehouses in Michigan and Ohio, filling them with engines from its Windsor and Essex Engine plants. “Just as soon as we get the engines done, we bring them over,” said Unifor Local 200 president John D’Agnolo. “We’ll do whatever we can to support Ford Motor Co.”

According to D’Agnolo, Ford Canada supplies 15,000 direct jobs at Kentucky Truck, Dearborn Truck, and Ohio Assembly. He warned that the tariffs could be disastrous for the F-150: “You won’t be able to sell a vehicle that will cost $20,000 more.”

The 5.0-liter V8s and Super Duty engines aren’t the only worry. The whole system runs on razor-thin margins and tight schedules. “They can’t just say, ‘I need you to increase it by another 1,000 engines,’” D’Agnolo said. “We don’t have the supply to support it.”

A 25% tariff could stall Detroit in two weeks

It’s not just engines crossing the Ford Canada border. Many Ford vehicles require crossing the river “five or six times,” as Ford transforms raw materials into components which it builds into parts which it shapes into sub assemblies which it puts together when it assembles the final vehicle. D’Agnolo said of the 25% tariff for each border crossing, “If it’s all of that, the company will have to shut down immediately.”

Ford CEO Jim Farley agrees. “A 25% tariff across the Mexico and Canada borders would blow a hole in the U.S. industry that we’ve never seen.”

While Detroit automakers get squeezed, foreign companies are poised to cash in. “It gives free rein to South Korean, Japanese and European companies,” Farley warned. Their U.S. plants wouldn’t face the same repeated tariffs. And for foreign-built vehicles, they’d only pay once.

The result? Foreign investors get a windfall while Detroit bleeds. They could undercut America’s most iconic trucks and muscle cars—and line their pockets doing it.