“It is not the biggest issue, but it is an issue,” he said recently while giving reporters a tour of a Louisville plant that has started making two aluminum-bodied sport-utility vehicles. The plant also makes Super Duty trucks.

Ford has no second thoughts about making the aluminum truck, Mr. Hinrichs added, noting that its light weight provides a smooth ride and increases towing and hauling capacity.

“Aluminum also allowed us to have a lot more capability in a truck, and that’s what people buy for,” he said.

The F-Series remains the nation’s top-selling vehicle line, accounting for a third of the cars and trucks Ford produces in North America and its biggest source of profits. Last year, Ford built more than one million F-Series trucks, and United States sales topped 896,000 — both the highest totals since 2005. The trucks commanded higher prices, too: They sold for an average of $49,552 in 2017, up more than $6,000 since 2014, according to Edmunds.com.

The company does not disclose the profitability of individual models, but analysts widely believe the margin on a full-size truck can be $10,000 or more. The margin on cars is often only a few hundred dollars, or less.

Ford’s chief financial officer, Robert L. Shanks, said the profit on F-Series trucks remained robust and rose in 2017. The trucks were “not a contributor to the decline in profitability at all,” he said. Rather, income was squeezed by development of electric vehicles and other new models, unfavorable foreign exchange rates and other rising costs, he said.