Auto sales for the month declined 5.5% year-over-year to 48,380 units from 51,205 units, truck sales also decreased 1.0% to 110,788 units, while SUVs sales rose 8.0% to 82,881 units as compared to a year earlier.
US sales of new vehicles are expected to fall 2 percent to 17.1 million in 2017, according to Kelley Blue Book.
In 2016, the US auto industry set another record, marking the seventh straight year that auto sales improved year-over-year.
At Fiat Chrysler, Jeep and Dodge posted declines of 12 percent and 23 percent, respectively.
"December capped off a record year for Ford brand SUVs, making it eight consecutive years of Ford brand sales leadership", said Mark LaNeve, Ford vice president of sales, service and marketing.
Sales of the Ford F-Series pickups rose 2.1% year over year in December to 89,385 units, and F-Series transaction prices rose $3,400 year over year to $47,800.
Toyota Motor North America reported December sales dropped 8.3% from December 2016 on a volume basis.
Charlie Chesbrough, chief economist at Cox Automotive, owner of the Autotrader online vehicle market and Kelley Blue Book auto appraisal service, stated the group expects 2018 sales to hit 16.7 million units and increasing rate of interest are one of the industry's obstacles this year as they increase month-to-month vehicle payments. The company also set a new annual sales record of 226,511 vehicles, a jump of 7.8% compared with all of 2016.
Investors were pleased GM had cut its inventory of unsold vehicles - a concern for the industry earlier in 2017 - at the end of December to 63 days supply unsold vehicles, beating its target of about 70 days supply. New vehicle sales in March are expected to top 1.4 million in the US, on pace for 14.6 million within the year.
"It's still a buoyant industry and the underlying factors that drive it are still very positive", Ford's USA sales chief, Mark LaNeve, said. Automakers are releasing monthly and annual sales numbers Wednesday. But most other automakers saw declines. Ford saw a decline of 0.9 percent, and Toyota was down 0.6 percent.
Ford's sales in the United States a year ago fell 1.1% to 2.6 million compared with 2016, but it reports a surprise increase last month, fuelled in part by the continued success of the F-Series pickups and other large vehicles.
GM also published its December sales figures Wednesday, which showed total sales were 2% up on the same month in 2016.
Sales at Toyota's Lexus brand fell 13.9 percent. GM's sales fell 3 percent.