Workers walk past parked General Motors Co. (GM) Chevrolet automobiles bound for export at the Port of Incheon in Incheon, South Korea.

Ford’s Chief Financial Officer Bob Shanks said its commodity costs during the quarter were about $300 million higher from last year, attributing about half of that to the U.S. tariffs on steel and aluminum. The tariffs are expected to eat up about $600 million in profit this year, he said.

GM said a higher-than expected jump in commodity costs and unfavorable exchange rates in Brazil and Argentina will cost it an extra $1 billion this year. Ford’s second-quarter earnings plunged by almost 50 percent and the company lowered its 2018 earnings projections.

All three are again trading down Thursday with Ford falling under $10 a share for the first time since 2012.

General Motors , the largest U.S. automaker, suffered its worst intraday drop in years, falling more than 8 percent Wednesday despite beating Wall Street estimates . Rival Fiat Chrysler plunged 16 percent Wednesday after missing earnings estimates, announcing the sudden death of CEO Sergio Marchionne and reducing earnings guidance for the year. Shares of Ford , which announced earnings after the markets closed, were under pressure all day.

Detroit automakers had a really bad day Wednesday as investors hammered Ford, General Motors and Fiat Chrysler after all three scaled back their 2018 earnings forecasts due largely to rising prices for raw materials.

Steel and aluminum prices have risen since the Trump administration imposed tariffs on the two key raw materials for the car manufacturing, steel and aluminum. Those costs could run even higher as President Donald Trump ratchets up his global trade war.

Trump said Wednesday that he was working with European Commission President Jean-Claude Juncker toward "zero tariffs, zero non-tariff barriers and zero subsides for the non-auto industrial goods."

Key details of the agreement were still unclear late Wednesday afternoon, but a deal not to impose further tariffs while negotiations are underway would avert a trade war between the United States and Europe. It would also represent a victory for the European Union, which had been bracing for new automobile tariffs as high as 25 percent.

Trump did not address whether the two leaders had reached an agreement on car tariffs, though Juncker said that no new tariffs would be assessed as negotiations proceed.

GM Chief Financial Officer Chuck Stevens told analysts Wednesday that consumers will bear some of the increased costs from the tariffs that are already in place.

"To the extent that we have opportunistic ability to pass along some [of the higher costs], we will," he said on a call with analysts. GM now expects to earn about $6 per share in 2018, down from its previous forecast of $6.30 to $6.60 a share, the company said in reporting its second-quarter earnings.

Car makers aren't the only companies getting squeezed by the tariffs. The trade penalties have been mentioned in some form on more than 40 percent of the 146 S&P 500 companies that have already reported second-quarter earnings this season, according to data compiled by CNBC.

On Tuesday, shares of Whirlpool plunged by more than 14 percent after the U.S.-based washing machine maker said higher steel costs will crimp its profits this year.

"Global steel cost has risen substantially and, particularly in the U.S., they have reached unexplainable levels," Whirlpool Chief Executive Officer Marc Bitzer told shareholders during the company’s conference call.

Harley Davidson estimated the tariffs will cost the motorcycle maker and extra $45 million to $55 million this year.

—CNBC's Leslie Josephs contributed to this article.