General Motors said Thursday that it will eliminate one of two shifts at a transmission plant in Warren, Michigan. The announcement is expected to put about 300 workers on indefinite layoff, or roughly half the plant’s total hourly workforce.

The move comes at a time when U.S. new vehicle sales are faltering after three record years — GM also on Thursday reported that its May numbers were off about 1 percent, compared to year-earlier sales. The decline has been especially severe on the passenger car side of the ledger, as millions of Americans shift from sedans, coupes, and sports cars to SUV, crossovers, and pickups.

GM already has been responding by trimming production of slower-selling vehicles, such as the Chevrolet Malibu, so “Recent actions to reduce passenger car production have caused us to adjust transmission production,” the automaker said in a statement.

Related: Have Crossover Sales Actually Hit a Peak?

Thousands More Layoffs Expected

In all, the largest of the Detroit Big Three has eliminated five factory work shifts since last November, when analysts and industry planners began to declare the downward momentum in car sales more than a temporary blip.

In all, about 5,000 hourly workers have been idled by moves that have impacted factories, including ones in Lordstown, Ohio; Detroit; and two in Lansing, Michigan. However, some of the production cuts are temporary and at least 700 workers are expected to be brought back as operations ramp back up next year.

GM is by no means the only automaker adjusting production and making cuts. A report by outplacement firm Challenger, Gray & Christmas shows that the auto industry had expected to cut 20,271 jobs last month. The vast majority of those came at Ford. The second-largest automaker suffered a 5.1 percent dip in sales during the first four months of 2017, though it reported an unexpected 2.2 percent increase for May.

But while May is likely to bring a slight reprieve in the downward sales spiral for the industry overall, that comes at a serious cost. According to a report by, incentive spending rose sharply on financing deals last month — by a whopping 33 percent.

Related: Popularity of Leasing Is Catching up with Automakers

Incentives have helped offset the fact that new car prices have been rising fast over the last several years. While last month’s average transaction prices — what customers actually pay for a vehicle, all in — were up from a year ago, they actually dipped $266 from April 2017, reported Kelley Blue Book.

Whether heftier incentives will be able to keep the market moving and forestall further job cuts is far from certain. Automakers are struggling to find the right balance between increased incentives and sales, knowing that if they get too aggressive with givebacks they could touch off the sort of profit-eating spiral that nearly destroyed two of the domestic manufacturers in the lead-up to the Great Recession, both GM and Chrysler surviving bankruptcy only with the help of federal bailouts.