U.S. auto sales continued their downhill journey in the last 10 days of August, moving 32.9 percent below their levels for the same period last year.

But foreign car manufacturers continued to increase their share of the domestic market, grabbing a record 32.7 percent of sales.

The five U.S.-based producers, including American Motors Corp. and Volkswagen of America, said they sold 164,616 cars between Aug. 21 and Aug. 31, down from 245,330 in the same period last year.

For the month, the domestic auto manufacturers sold 409,411 cars, a 32 percent drop from the 601,741 sold in August 1981.

"There isn't that much encouragement" in the latest car sales figures, said David Healy, an analyst with New York-based Drexel Burnham Lambert Inc. "But I think we're building up for a big recovery."

Healy said lower interest rates and more moderate sticker price increases will bring customers back to dealer showrooms. The recent drop in the prime interest rate to 13.5 percent, and General Motors Corps.'s announcement that it will cut prices on its 1983 models help to create a climate for an auto consumer revival, Healy said.

L. Ray Windecker, an analyst at Ford Motor Co. said that car sales will improve, largely because Americans soon must replace the aging models they're driving today.

Chrysler Corp., the third-largest U.S. auto company, said it sold 18,637 cars between during the latest 10-day period -- a 42.4 percent drop from the 32,354 sold in the same period a year ago.

Ford Motor Co., the second-largest domestic car company, said its sales fell 27.1 percent, from 52,734 to 38,424.

GM, the domestic industry leader in terms of market share, said it sold 101,867 cars in the last 10 days of August, a 31.6 percent decline from the 148,995 cars sold by the company during the same period last year.

AMC sales were estimated at 1,807, down 51.4 percent from 3,722 a year ago, while VWoA reported 3,881 vehicles sold, down 48.4 percent from 7,525 last year.

The import companies, meanwhile, reported selling 198,980 cars last month, up 1.5 percent from the 196,058 sold in the same period last year. Their 32.7 percent share of the domestic market tops the record 31.9 percent share of last December.