Marvin Runyon sat in his blue-collar uniform with his first name embroidered over the pocket and spoke last week of the team spirit and open communications between workers and managers under the 69-acre roof of the new Nissan truck plant here.

Contrary to appearances, he was not one of the production-line workers, known here as "technicians." Once an admittedly autocratic Ford Motor Co. executive in coat and tie, Runyon, 58, has become down-home, consensus-building "Marvin" now that he is president of Nissan's U.S. operations and in charge of this futuristic factory rising out of the cow pastures 18 miles southeast of Nashville. At $660 million, it is the largest investment in the United States by any Japanese company.

It boasts 220 robots to work beside 2,000 Middle Tennessee humans whose selection from among 120,000 applicants was based in part on ability to be "team players." It has laser-controlled paint guns, streamlined die-changing, common cafeterias and uniforms for workers and bosses, Ping-Pong and picnics, wages competitive with industry averages, workers trained in many skills instead of just one, only half as many management levels as Detroit auto makers and, in contrast to old-style tough Detroit straw bosses, supervisors who are required always to "enhance or protect the workers' self-esteem."

In short, it is an expensive selection of what Runyon and his staff deemed the best of both American and Japanese technology and philosophy, assembled from the ground up. "A once-in-a-lifetime chance," Runyon said.

In an industry where union organizers once fought club-wielding management goons for workers' basic rights, such an enlightened approach might have been hailed as industrial nirvana. Instead, it is a beam in the eye of the United Auto Workers union.

As Runyon drove the first Nissan pickup off the production line here Thursday, UAW president Owen Bieber issued a statement reiterating the belief of union officials that organizing the plant is a must, lest their negotiating powers be undermined in the industry.

The workers "have been led to believe they are the beneficiaries of a Japanese-style experiment in cooperative management which makes a union unnecessary," he said. "We respectfully remind Mr. Runyon that Henry Ford, the founder of his former employer, likewise believed a union could not improve the condition of Ford workers."

However, Nissan workers such as Frank Johnson, 29, present the union with a diffcult task. He grew up in a farm family of 14 and previously belonged to the machinists' union while working at a Tennessee air conditioner assembly plant. "I believe unions have outgrown the intentions of what they was organized for," he said. "If you're going to do your job, and the company is going to recognize that things are changing and treat you fair, you don't need no third party talking for you."

Johnson, who works in the paint booth touching up places missed by machines, was one of 383 employes, including 128 production-line workers, taken to Japan by Nissan to study Japanese teamwork and other techniques.

If something works he believes it's natural for Americans, "modern and open-minded as we are," to borrow it from the Japanese, Johnson said. Noting that he has been interviewed several times by reporters and TV crews, he added, "I get tired of hearing that question: how does it feel to be working for those Japanese. This is an American plant."

Tennessee state officials of both parties, led by Gov. Lamar Alexander, courted and aided the Nissan invasion. The legislature approved construction of 12 miles of new road to the plant site--which some unionists who had fought in World War II suggested dubbing Pearl Harbor Boulevard. Top Nissan officials are temporarily housed in a shut-down Air Force base while their permanent administrative offices are being completed.

The state also contributed $7 million to Nissan's unusually extensive $63 million screening and training program for employes. Nissan, in turn, agreed to hire Tennesseans instead of bringing experienced, unemployed auto workers from out of state. (Only two vice presidents here are Japanese, plus a few dozen Japanese to aid in the start-up and some 10 employe families.)

Union officials have accused Nissan of looking for a docile workforce of "peasants" in a state hostile to organized labor. But Nissan officials said they were simply seeking capable workers without too many "preconceived notions" who will fit in with the plant's "participatory management" style.

Beverly Myers, 27, and her husband, Bruce, both work for Nissan. She puts on brake tubes, air conditioning, rear carpets, door locks and other jobs the robots can't do. A former factory worker, she applied two years ago and says she had to go through a test, three interviews, over six weeks in the company's unpaid training program nights and weekends, and another interview.

At the union plant she worked in before, she said, "If somebody picked up something they wasn't supposed to, somebody'd go file a grievance. It was too picky for me." At Nissan, she said, "I've learned every job in my zone--19 different jobs."

She and the other workers meet every morning with their supervisors and talk about everything from softball to problems on the line. "They want you to come to them if something's wrong . . . . They want you to be happy and not dread coming every day. That way, absenteeism stays down and quality stays up and they'll make more money in the long run."

She said she sees the union as a potential threat to what she considers a good deal. Recalling a rubber workers' strike that threw her husband--a former union member--out of work at a nearby tire plant (which has also been taken over by a Japanese company), she said, "Unions have given us some bad times."

While the workers, new to the auto industry, have not yet developed "bad habits," officials said, the managers are another story. Many of them came from Ford or other American auto companies and they speak of the old traditions like smokers trying to quit.

"When you're in an autocratic environment, you tend to respond in an autocratic way," said Runyon. In changing styles, "We have to fight the old tendencies. It's tough when you know what you want to do but you are reaching a consensus decision. It takes longer."

For example, the workers are still trying to reach a consensus on how long they should take for lunch. "In the old days, management would use that and keep it as a sacred decision," said paint plant manager Emil Hassan. "Here, there's a lot of pain in making that decision . . . . So far, 45 minutes seems good."

Sometimes, management may decide not to go for consensus, said Runyon. "This is participatory management, but it is not permissive management. We'd have an awful looking truck if it was."

The plant is just beginning to turn out trucks, aiming to produce 10,000 a month by mid-1984. UAW officials predict that once the line speeds up next fall, things will get tense, Runyon and company will revert to their old ways, and the workers will begin to realize they need a union after all.

"They're right when they say things will get tenser," said Nissan personnel specialist Larry Seltz. "There will be pressure and tempers. The question is how we deal with it."

Said paint technician Johnson, " Manager Emil Hassan told me it's not going to be easy. Not just glory, glory. Sure we're going to have to work harder, and the union can't change that. If things start going to pieces next fall, then people working here have misled themselves."