Joan Claybrook, chief highway safety administrator in the Carter administration, rejoined the Ralph Nader organization yesterday as president of Public Citizen, the umbrella group at the center of Nader's lobbying ventures.

Claybrook's return provided a unique variation on the Washington revolving-door theme and represented a reconciliation of sorts between two former allies and close personal friends who had a celebrated, front-page falling out during the Carter years when she was running the National Highway Traffic Safety Administration.

Angered that Claybrook publicly supported, while philosophically disagreeing with, a decision to allow the auto industry to delay installation of airbags, Nader called for her resignation from NHTSA.

That was in late 1977, eight months after she had taken office. But Nader charged that during that period, Claybrook had "etched a trail of averted or broken promises."

In a subtle dig at her former ally, Claybrook had responded that she was "fully aware" of the complexities of running a regulatory agency, an experience Nader has not had.

The feud took on a life of its own, becoming an issue in a seminar on responsibilities of reformers working in government and the subject of columns and editorials on the obligations of the "outsider" become "insider."

It was a dilemma in an era that has passed. The reformers are all back on the outside again, and the talk now from Claybrook and Dr. Sidney Wolfe, whom she replaces as the head of Public Citizen, is of battles ahead as the Reagan administration seeks more relaxed safety standards and fewer federal government regulations.

Wolfe said he is stepping aside to devote full time directing the health research arm of Public Citizen.

"The Reagan administration is killing and injuring too many American people for me to spend less than 100 percent of my directing the Health Research Group's effort to counteract this violence," he said.

Claybrook, who said she is completing a book-length study on success stories coming out of health and safety regulations, talked about her plans for helping fledgling consumer and public interest organizations and for issuing reports that chart the relationship between votes in Congress and campaign contributions.

"The Reagan administration has really not attempted to honestly take the least beneficial regulations and remove them, but has attacked the ones most beneficial to consumers," Claybrook said.

Wolfe said the administration had been a boon to the Nader organizations, citing increased contributions from worried consumers and a renewed attraction of top graduates of colleges and law schools.

Public Citizen includes health, antinuclear, lobbying and litigation units. Nader resigned as head of Public Citizen in October, 1980, to free himself of managerial responsibilities and spend time building an endowment for the organization.

Nader did not attend the press conference to announce Claybrook's return but later expressed enthusiasm about it, noting that during the period when he was calling her tenure in government a failure, he had also said he thought she could be more effective on the outside.

" . . . It's the difference between an eagle trying to fly in a tunnel and eagle trying to fly in the air," Nader said lightly.

But he was unbudging about the issue of requiring installation of automobile air bags that had prompted the dispute.

"She admits I was right," he said.

"I never disagreed with him on the substance," Claybrook acknowledged in a separate interview. But, she said, "It was a very tough attack by Ralph and, I felt, a little bit unfair at the time."

"History is history," Nader said.

"I think that you have to go on and live life," Claybrook said with the hint of an edge in her voice. "I don't think you can sit and fret about the past."