General Motors Corp. will lay off about 400 workers at its Hamtramck, MI, assembly plant, part of an effort the auto maker announced last month aimed at slowing production at three U.S. facilities.

GM says the assembly line slowdowns will help it align capacity with consumer demand, which has eased dramatically this year due to high gas prices and a sputtering economy.

The 400 layoffs at Hamtramck, which builds the Cadillac DTS and Buick Lucerne large luxury sedans, will slow the line to 38 vehicles per hour from 56. It will trim hourly employment at the plant to about 1,100 people, effective Jan. 12.

Sales of the DTS fell 32.4% through September, while Lucerne deliveries tumbled 32.0%, according to Ward’s data. Industry-wide, large-car sales were down 27.8% and luxury sales slipped 11.3%.

GM also plans to slow assembly at its Pontiac, MI, facility to 24 vehicles per hour, from 55, effective Feb. 2, resulting in 700 layoffs. Pontiac builds the Chevrolet Silverado and GMC Sierra fullsize pickups.

GM additionally will eliminate the second shift at Wilmington, DE, laying off 400 workers Dec. 8. Wilmington builds the Pontiac Solstice and Saturn Sky roadsters, as well as the Opel GT roadster it exports.

GM announced earlier this week it moved ahead closure of its Janesville, WI, fullsize SUV plant from the end of 2010 to Dec. 23. Last month, the auto maker said it would close its Moraine, OH, midsize SUV plant on Dec. 23, instead of the end of 2010.

GM also plans to close a fullsize pickup-truck facility in Oshawa, ON, Canada, and will cease medium-duty truck production in Toluca, Mexico, as part of its strategy to align production with a shift in consumer demand to more fuel-efficient vehicles.

A GM stamping plant in Grand Rapids, MI, also fell victim this week to the production adjustments. The facility, which will close by the end of 2009, employs about 1,340 hourly workers and 180 salaried personnel.