Chrysler Corp. said today it is expanding to four additional cities the brash test-drive promotion that gives $50 to car purchasers -- even if they buy a competitor's product.

Chrysler said the program will begin today in Columbus, Ohio; Portland, Ore.; Denver, and Richmond, Va.

It was tested initially beginning Dec. 4 in Kansas City, where a Chrysler official said it successfully stimulated car sales.

"Success of the promotion in Kansas City reinforced our theory that if serious buyers compare our products head-on with competition, a big percentage of them will buy a Dodge, Chrysler or Plymouth," said Jerry Pyle, Chrysler's vice president for U.S. automotive sales.

U.S. automakers began 1980 with a 75-day supply of cars -- the highest for the date since the recession of 1975 -- including an unusually high carryover of 1979 models.

General Motors Corp. and Ford Motors Co. have extended until Jan. 31 the cash incentive programs dealers can use to trim car prices, but Chrysler has been experimenting with new marketing programs.

The ailing no. 3 automaker, currently trying to pull together financing to qualify for $1.5 billion in federal loan guarantees, let its $300 direct customer rebate program lapse on Dec. 31.

The test-drive promotion pays $50 to consumers who test-drive a Chrysler product and then buy a new car within 30 days, even if they purchase a competing model.

Chrysler said 15 dealers in the metropolitan Kansas City area gave 685 test drives during the 30-day promotion. Of those, 554 bought Chrysler products and only 12 purchased another brand, the company said.

Sales in December were up 35 percent over the same period a year ago in the Kansas City area, Chrysler said.

"We put our money where our confidence was in Kansas City and it paid off," Pyle said. "Now we are about to do the same in Portland, Columbus, Denver and Richmond."

Chrysler also is conducting an experimental promotion in Salt Lake City that will refund the car purchase price within 30 days to any unsatisfied buyer. The company has not reported results of that program.

In a separate development, first results of voting on a second sacrificial contract with Chrysler Corp. show "overwhelming" approval, officials of the United Auto workers Union said today in Detroit.

Members of Local 212 in Detroit voted 3,047 to 576 to ratify the contract calling for an additional $243 million in concessions to the troubled automaker.

Congress required the new contract as another condition for its approval of $1.5 billion in loan guarantees. UAW members already had approved $203 million in contract concessions in October.

UAW president Douglas A. Fraser said in Washington that a local in Newark, Del., had given similar backing to the new pact.

Voting by Chrysler's 110,000 UAW members is expected to be complete by the end of the month.

Meanwhile General Motors Corp. in Detroit and Ford Motor Co. in Dearborn, Michigan, today announced temporary production cutbacks to cut inventories.

General Motors said it will temporarily halt production of full-sized cars on one line at its Oldsmobile plant in Lansing, Mich., next week, idling 1,600 hourly workers.

Ford Motor Co. said it will suspend passenger car output for two weeks at its Wixom, Mich., assembly plant and for one week at its Lorain, Ohio plant, temporarily idling 7,500 hourly workers.

In addition, Ford said it will halt truck production for one week at its Norfolk, Va., assembly plant and its Louisville, Ky. plant, temporarily idling 5,800 hourly workers.

Both General Motors and Ford had previously reported other temporary shutdowns, affection a total of almost 20,000 hourly workers.