Originally Published: 03 JAN 24 13:05 ET

By Chris Isidore, CNN

New York (CNN) — The strike at General Motors plants in September and October took a bite out of its fourth-quarter sales, but strong demand for the vehicles made at its other plants allowed the company to report a narrow gain in US vehicle sales overall.

The strike ran from September 15 through a tentative agreement reached with the United Auto Workers union on October 30. And the differing impact could be seen in the sales figures reported by GM Wednesday.

The UAW strike was a targeted action against specific assembly plants of all three companies. There were a dozen models that are built at the three GM plants that went on strike for more than a couple of days - Wentzville, Missouri, Arlington Texas and Lansing-Delta Township in Michigan, in addition to the Fairfax plant in Kansas City, Kansas, which was shut by the lack of parts being produced by the nearby Wentzville plant.

While GM’s statement on sales did not mention the strike or its effect on sales, those 12 models saw sales in the quarter fall 27.5%, according to analysis of the numbers by CNN, while models built at other plants had sales increase 14% compared to the year-earlier quarter.

Sales of GM’s two full-size pickups, the Chevy Silverado and the GMC Sierra, rose only 3% in the quarter, despite the fact that production of those models were not affected by the strike. That’s down from the 14% growth rate reported for those models in the first nine months of the year.

“In 2024, we expect industry sales to remain strong and we’re excited about the opportunities ahead as we expand customer choice with new vehicles,” said Marissa West, president of GM’s North America unit.

Through the first three quarters of 2023, GM sales were up 19% compared to the same period of 2022. With the essentially flat sales in the fourth quarter, it ended the year up 14%.

But some slowdown was likely to have happened in the fourth quarter even without the strike, as the first nine months of 2022 saw weak sales due to a shortage of parts, particularly computer chips, needed to build new cars. That choked supplies on dealers’ lots and drove up prices. Supplies of those parts had started to improve by the fourth quarter of 2022, making comparisons more difficult.

“The growth was bound to not be as rapid as it has been,” said Michelle Krebs, executive analyst with Cox Automotive. “The upshot of what we’re seeing is that December ended pretty strong. We do know there was wheeling and dealing at dealerships at the end of the month.

Stellantis, one of the other automakers that was struck by the UAW, is due to report results later on Wednesday. It went into the strike with a larger inventory of vehicles on hand than the other two unionized automakers. Ford, the third automaker hit by the targeted strike, is due to report sales on Thursday.