DETROIT - General Motors Co said on Tuesday that it would add shifts at three U.S. assembly plants, restoring 2,400 jobs, as it shutters other facilities or prepares them for new products.

The addition of shifts at plants in Kansas, Indiana and Michigan comes at a time when U.S. auto industry sales are thought to have hit bottom and manufacturers are raising production to restore depleted vehicle inventories.

U.S. dealer inventories were trimmed sharply after the federal government's cash for clunkers program lifted sales in July and August with incentives of up to $4,500 to turn in gas-guzzling vehicles and buy new more fuel-efficient models.

GM said about 600 other jobs at related stamping, engine and casting facilities would be restored as well.

The company said it would add a shift at its assembly plant in Fairfax, Kansas, in January. Fairfax will become the sole builder of the Chevrolet Malibu sedan when GM ends production in Orion, Michigan, to retool that plant for small car production.

In April, GM plans to add a shift of heavy-duty pickup production in Fort Wayne, Indiana. The company is closing its Pontiac, Michigan, plant at the end of September.

GM also plans to add production of the Chevrolet Traverse SUV at its Lansing Delta Township, Michigan, plant in April. Production of the Traverse at GM's plant in Spring Hill, Tennessee, will end in November, and that plant will be put on standby status.

Earlier in September, GM said it expected to build 535,000 vehicles in North America in the third quarter and 655,000 in the fourth quarter, down about 20 percent from a year ago. (Reporting by David Bailey and Bernie Woodall; Editing by Lisa Von Ahn)