The Education Department has reassigned its top student aid administrator at a time that the department is rushing to resolve the financial troubles of a large student loan guarantor.

The department has also requested financial data from other loan guarantors nationwide and has sought outside financial expertise in evaluating the condition of the Higher Education Assistance Foundation (HEAF) and various proposals to take over the nonprofit organization based in Overland Park, Kan.

Members of Congress have accused the department of lax oversight of loan guarantors and have suggested officials should have detected the severity of HEAF's problems earlier. The prospect of its financial collapse has made bankers nervous just as the peak season for processing student loans approaches. HEAF has guaranteed $9.6 billion in loans made by banks.

Etta Fielek, a department spokeswoman, denied that the transfer Friday of Roberta B. Dunn, who had been deputy assistant secretary for student financial assistance, was connected to HEAF's difficulties.

"It is not related to HEAF. Bobbi is a tremendously talented person," Fielek said. "She was agreeable to the change."

Fielek said Dunn would become a senior adviser on postsecondary education in the Office of Education Research and Improvement, which gathers school data, makes research grants and evaluates educational projects. Dunn has been assigned to a division concerned with educational improvements.

Two congressional sources doubted that Dunn voluntarily relinquished a management job with line responsibility for overseeing the department's largest programs. "I suspect it is probably involuntary," one source said.

Dunn, a former education adviser to Sen. Orrin G. Hatch (R-Utah), could not be reached for comment.

Her acting successor overseeing student aid programs is Ernest C. Canellos, formerly chairman of the Education Appeals Board, a department unit being replaced by administrative law judges.

Yesterday was the deadline for student loan guarantors nationwide to complete and return a five-question survey on their finances, a survey that the state or nonprofit agencies received from the department Friday. According to Fielek, the survey asks for information on guarantors' loan portfolios and default rates as of June 30, 1990. The latest audited financial report is also requested.

"We felt a need to develop the most up-to-date information on all guarantors across the board. It helps provide a bigger picture to the whole loan program," Fielek said.

Some data requested in the survey are not covered in quarterly reports that guarantors file with the department. Joseph M. Cronin, president of the Massachusetts Higher Education Assistance Corp., said the guarantor was asked to reveal its mix of two-year, four-year and trade school loans.

"We've been saying that HEAF has too many trade school loans. We want to see what the others have," Fielek said.

David V. Evans, staff director of the Senate Labor and Human Resources subcommittee on education, arts and the humanities, said it was about time the department took a financial survey of the nation's 55 loan guarantors.

"They should have sent it out a long time ago," Evans said. "I'm not so sure the department has been on top of this program as it should be. . . . I think they need to intensify their {monitoring} efforts considerably."

Undersecretary Ted Sanders has said five to seven smaller guarantors may have less severe financial problems, but he has declined to identify them. Fielek said that was something the department may never do.

Fielek said that the department had purchased 72 hours of consulting time from Kidder Peabody & Co. to evaluate HEAF's finances and proposals to assume control of its loan portfolio and operations. She said the outside consultants were needed for their experience with big financial transactions.