General Motors Corp. will idle assembly plants in Michigan and Kentucky for an extra week this year as it continues to right-size inventories with sagging consumer demand.

GM says it plans to shut down its Hamtramck, MI, facility outside Detroit for a week beginning Nov. 1. Hamtramck builds the Cadillac DTS and Buick Lucerne fullsize sedans and learned earlier this year it also would suffer 400 layoffs, slowing the linespeed to 38 vehicles per hour from 56.

The Hamtramck cutbacks will trim hourly employment at the plant to about 1,100 people, effective Jan. 12.

Sales of the DTS in the U.S. 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%.

DTS inventories at the end of September stood at 50 days’ supply, and Lucerne was at 70 days.

GM also plans to idle its Bowling Green, KY, assembly plant for one week beginning Dec. 1. Bowling Green builds the Chevrolet Corvette and Cadillac XLR sports cars. Sales of the Corvette are down 9.5% so far this year, while XLR deliveries are off 26.3%. Corvette inventories sit at 95 days and the XLR at 215, Ward’s data shows.

Auto makers report October sales next week.

The production changes come as GM wrestles to match inventories with sluggish demand and perhaps take over Chrysler LLC, whose inventories are even more bloated. GM Chairman and CEO Rick Wagoner reportedly has met with lawmakers in Washington in recent days to push for government aid to absorb its cross-town rival.