Before suppliers can start moving production, there are at least two great unknowns.
1. Whether higher import barriers get approved, and how high they would be.
2. Based on those factors, how the automakers would react.
American Axle & Manufacturing Holdings CEO David Dauch said in a separate conference call this month that his company prefers to manufacture parts in "close proximity" to the automaker plants where they are used.
"The Trump administration needs to clearly articulate and communicate their policies," Dauch said. "The OEMs need to digest that, and clearly they've had some discussion with them.
"And they've got to determine their plant-loading strategies. Once they determine their plant-loading strategies, then we clearly can determine our plant-loading strategies."
Comments made in recent supplier conference calls suggest that companies are more likely to leave the more labor-intensive operations in Mexico, where low labor costs are proportionately a bigger advantage over U.S. manufacturing. High-tech components, and parts that could be more automated, are more likely to move to the U.S. because labor represents a smaller percentage of their value.
Delphi Automotive CFO Joseph Massaro offered similar reasoning in his conference call this month. Delphi supplies electronic systems and powertrain and active safety technology.
"There are certainly more automated-type manufacturing processes down there, which you could conceivably see coming back -- or coming -- to the U.S.," Massaro said. "Some of these were never in the U.S. We've grown them in Mexico or started them in Mexico."
In Lear's case, Simoncini said higher tariffs could affect different parts in different ways, even within the same product line. Making seat covers is labor intensive, he said of Lear's operations, so it would probably stay south of the border "even with increased taxes."
But Mexican electronic components, the underlying seat structures and foam cushioning could probably move to the U.S., he said.
Shipping costs are another consideration, Simoncini said. Seat covers would be more likely to stay in Mexico because they stack compactly and are shipped more easily and cheaply than the underlying seat structures, he said.
Several multinational suppliers maintain that they are flexible enough to respond quickly and economically, once they know what to expect on trade rule changes.
BorgWarner CEO James Verrier told analysts that his company's annual cross-border sales with Mexico represent about $200 million of about $9 billion in annual worldwide revenue.
"That's a manageable situation, particularly with the flexibility of our footprint," Verrier said of the engine and drivetrain parts supplier.