When Fred W. Cords came to Tokyo two weeks ago with the large American trade mission, his goals were modest: to make a few contacts and test the Japanese market for his Minnesota automotive company's line of braking equipment for big trucks.

He accomplished that and not much more. He got no orders, but one company asked for a quote on a brake valve and indicated he is to get an order in about 30 days.

It was enough to send Cords back to North Mankato, Minn., planning to try Japan again, next time through a large Japanese trading company that will market and distribute his products.

"For me, this was a development mission and it accomplished exactly that," Cords said.

His experience is roughly typical of the 68 American companies that sent representatives along on the largest U.S. trade mission to tackle any major export market, part of a government plan to open a new business front in Japan.

There were no home runs and quite a few strikeouts, but most of the businessmen interviewed this weekend said they found enough interest to merit a serious sales drive in Japan.

Frank A. Weil, the assistant secretary of commerce who led the delegation, said his tally showed that 80 percent of the companies reported some degree of success and that 25 percent either made contracts or had definite prospects.

Japan's officialdom, stung by repeated claims that markets here are artificially barred to foreign competitors, rolled out the red carpet for the delegation, setting up hundreds of interviews to make sure the businessmen were well received.

There was also a widespread suspicion that some of the impromptu sales were setups, intended to make the mission a temporary success in public relations terms.

For example, several businessmen reported seeing letters written to Japanese company officials by the Ministry of International Trade and Industry instructing them to cooperate with the Americans.

"Some of the Japanese businessmen have told the Americans who called on them that they were there to meet them because MITI told them to be there," said Well.

Some of the American businessmen ran into the same sort of intricate barriers that foreigners have always claimed made selling in Japan nearly impossible. One tactic was to refuse to describe specifications for the products they need to buy.

A New Jersey scientific equipment firms representative, William J. Recker, said he ran head on into Japan's complicated distribution system in which a company buys only from longtime friends or relatives and refuses to consider foreign competitors.

"It's such an incestuous relationship," Recker said, "that it would take years to break into. It's such a closed community." Recker's firm, Fisher Scientific Co., has found it can sell in Japan those products that do not compete with Japanese-made products, but it hits a stone wall when selling those that are available here. However, Recker said he sees a chance of obtaining a small percentage of the market and went home intent on persuading his boss to open a Japanese office.

Weilalso cited one instance of a government corporation trying to keep the barriers high. He said an American company, Digitech, Inc., found customers ready to buy their line of test equipment for data transmission lines if they could get permission from Nippon Telephone and Telegraph. So far, Weil said, Nippon has refused even to spell out standards on which their approval or disapproval would be based.

That and similar cases will be referred to the year-old Trade Facilitation Committee, a joint U.S.-Japanese complaint referral service that has had limited success in poking holes in bureaucratic barriers.

Other businessmen found that much of their sales pitch time was spent discussing the intricate rules and regulations evolved over the years by Japanese government agencies for handling imports.

Cords, the Minnesota automotive parts representative, said his contacts inevitably first raised the problem of getting approval from the Ministry of Transportation.

"I had boned up on that subject before I got here," said Cords, "and was able to get past it pretty quickly just by quoting the law back at them. But the other guys tell me 25 percent of their time was spent talking about administrative hurdles."

Weil said he is convinved there has been "a real change" in attitudes among top business and government leaders anxious about the closed market criticisms.

"My own sense is that there is the beginning of a real change," Weil said. "But it may take five years for that to seep down into the lower levels of the bureaucracy."

With the exchange rate fluctuations operating in their favor, many Americans found it would be easy to beat prices of Japanese competitors on their own grounds. The rapid appreciation of the yen against the dollar has made American products considerably cheaper here in the past year. Cords, for example, found he could undersell Japanese manufacturers by about 20 percent on most of his line of power steering and braking equipment.

Few of the American businessmen were as unequivocally enthusiastic as Frank K. Girardin, vice president of the small Empire Tool Co. in Memphis, Mich. He got a warm welcome at Toyota and Nissan, two giant automakers to whom he hopes to sell small machine tools.

"They were open and eager," said Girardin. "We're competitive in prices and if I'd wanted to closer a deal now I feel sure I could have. I kick myself in the tail for not getting myself over here before."