Major automakers on Thursday posted a weak finish to the year for U.S. new vehicle sales but remained bullish on the outlook for the economy even as much of the industry braced for what is widely expected to be a worse year in 2019.

"Despite recent market turbulence, the data we have in hand suggests an economy that remains on solid footing heading into the new year," Ford Chief Economist Emily Kolinski Morris said on a conference call. "Consumers seem to be looking through market volatility to focus on continued positive job and income conditions."

But Cox Automotive analyst Michelle Krebs said an overhaul of the U.S. tax system boosted sales in 2018, adding that consumers moved up their purchases on concerns the Trump administration would impose tariffs as well as fears of rising interest rates.

American consumers have gradually been abandoning passenger cars in favor of larger, more comfortable SUVs and pickup trucks that are far more profitable for automakers.

Ford reported an 8.8 percent drop in sales for December, with declines in passenger cars, SUVs and pickup trucks.

Sales of Ford's F-Series pickup trucks, the top-selling U.S. brand since the 1980s, fell 1.8 percent in December and its SUV sales were off 4.4 percent.

The automaker's transaction prices rose $1,600 in December to a monthly record of $38,400 per vehicle, U.S. sales chief Mark LaNeve said, driven by the consumer shift from sedans to SUVs and pickups.

Ford executives said the automaker will switch to reporting quarterly sales like main rival General Motors which stopped reporting on a monthly basis last spring, arguing that a 30-day snapshot was too small a window to accurately reflect market conditions.

GM on Thursday reported a 2.7 percent drop in fourth-quarter sales, with declines for Chevrolet, Cadillac and Buick brands.

The No. 1 U.S. automaker also posted declines for some of its more popular larger vehicles, including the Chevrolet Suburban, the Cadillac Escalade and the GMC Yukon, all high-margin SUVs.

GM reported a small decrease for its Silverado pickup truck as it transitioned to a new, revamped model.

The automaker expects U.S. new vehicle sales industrywide to hit 17.3 million units for 2018, a slight increase versus 2017.

While analysts have estimated that 2019 will be a down year, automakers were upbeat about the market.

"We are very bullish on pickups heading into 2019," Kurt McNeil, GM's U.S. vice president for sales operations, said in a statement. "We feel confident heading into 2019 because we have more major truck and crossover launches coming during the year and the U.S. economy is strong."

Toyota's December sales dropped 0.9 percent from the same month in 2017. The Japanese automaker said passenger cars were down 16.5 percent, including its flagship Camry sedan, which slid 32.9 percent. It posted strong gains in SUV and pickup truck sales.

Fiat Chrysler bucked the trend for December, posting a 14 percent increase in sales. Its key Jeep and Ram brands were up 10 percent and 37 percent, respectively, in December. Ram pickup truck sales were up 34 percent in December.

"This year's performance underscores the efforts we undertook to realign our production to give U.S. consumers more Jeep vehicles and Ram pickup trucks," Reid Bigland, FCA's head of U.S. sales, said in a statement. "We see sales remaining solid in 2019."

A large portion of the gains came from higher sales to rental car companies, corporations and government agencies.

Nissan sales were up 7.6 percent as strong truck and SUV sales offset a decline in passenger cars. Despite the strong finish to the year, Nissan's U.S. full-year sales were down 6.2 percent versus 2017.

Ford shares were down 0.5 percent at $7.86, FCA fell 1.3 percent at $14.15 and GM dropped 3.2 percent at $32.55.

After a long bull run, U.S. new vehicle sales were expected to drop in 2019 as rising interest rates weigh on sales and translate into higher monthly car payments for consumers. Recent stock market turmoil and uncertainty over the health of the U.S. economy could also add to consumer caution in the short term.

While passenger car sales have fallen rapidly, a pick-up in profitable trucks and SUVs are expected to remain relatively robust despite an overall decline in sales.

Based on a forecast that includes two interest rate hikes this year, Cox Automotive forecasts auto sales of 16.8 million units in 2019.

"Higher interest rates are the biggest risk we see at the moment," Krebs said.