Chrysler Corp. board Chairman John Riccardo announced yesterday he will seek early retirement, "effective immediately," from the ailing automobile manufacturer.

Riccardo's departure was seen as evidence of Carter administration pressure for changes in Chrysler's top management, prior to any endorsement of loan guarantees the company is seeking.

Riccardo, who was due to step down in December as chief executive in any event, will make his retirement request at a Chrysler board meeting Thursday.

As chairman and chief executive, Riccardo is expected to be succeeded by Lee Iacocca, the ousted former president of Ford Motor Co. who was hired as Chryser president last November by Riccardo. At the time, Riccardo told reporters that Iacocca probably would be named chief executive in about one year.

Riccardo's announcement yesterday came 48 hours after the company was rebuffed by Treasury Secretary G. William Miller in its request for $1.2 billion in federal loan guarantees. Miller termed the request "way out of line."

Last month, President Carter told a town meeting in Burlington, Iowa, that any government aid package would require Chrysler to "reconstitute their management." Miller made a similar point on Saturday, stating that while any management shift must be made by Chrysler's board, "I'm sure" that before a final plan goes to Congress, a decision on future management resources would be made.

Riccardo said yesterday he will seek early retirement for two reasons -- health and the company's need to have a new management team in place.

He said that he had been hospitalized earlier this year because of a heart problem," and advised by physicians to retire immediately. "However, I felt at the time that in view of Chrysler's serious situation I should stay on until the end of the year in order to provide the funds necessary to return Chrysler to profitability," he stated.

Moreover, "there is no question that even though I have actively addressed the major problems facing Chrysler, in the minds of many I am closely associated with the past management of a troubled company," Riccardo added. "It would be most unfair to the new management and the employes of Chrysler if my continued presence as board chairman should in any way hinder the final passage of our request for federal loan guarantees."

Both Riccardo, 55, and Iacocca recently agreed to give up all but one dollar of their $360,000 annual salaries for two years. Iacocca will be 55 years old next month.

A Chrysler spokesman said yesterday he does not know if the directors will seek to keep Riccardo as a board member when they meet in Detroit on Thursday.

Officially, the company also declined to comment on a possible successor to Riccardo but the outgoing chairman said yesterday, "In my judgment, Lee Iacocca is one of the foremost automobile men in the industry . . . I am absolutely confident that under his leadership the company will return to the position of eminence that it deserves."

To a large extent, Chrysler's future depends upon some form of federal aid and negotiations were reported to be continuing yesterday on the final shape for a loan guarantee package to keep the automobile company in business.

A Chrysler spokesman said the plan submitted by the company on Saturday was "basically our plan," and that no changes are contemplated. Other sources said they expect a revised Chrysler proposal to be submitted after the board meeting -- either late this week or within the next two weeks at the outside.

One person familiar with the Chrysler-Treasury talks described the current situation as "kind of an economic-political process . . . they're testing each other with Miller holding their feet to the fire and Chrysler trying to get the most it can."

Officially, the Treasury declined to comment on Riccardo's announcement but a spokesman for the department said that the big accounting firm of Price Waterhouse & Co. has been approached and asked to study the financial plan submitted by Chrysler on Saturday. Several Wall Street investment banking firms also have been asked for free advice to the government about financial prospects for the nation's third-largest auto firm and tenth-largest industrial corporation.

One firm that turned down the Treasury yesterday was Lazard Freres & Co., which worked as a financial adviser to Chrysler from last fall until May. Felix Rohatyn, a Lazard partner, said last night he had told Deputy Treasury Secretary Carswell yesterday that because of a "potential appearance of conflict of interest," the New York firm could not take part in any assessment.

On Capitol Hill, meanwhile, members of the key banking committees that would have jurisdiction over loan guarantee legislation said they were remaining on the sidelines while Treasury and Chrysler seek a compromise. Senate Banking Committee Chairman William Proxmire (D-Wisc.) has flatly opposed loan guarantees for the auto company but has forecast that such a program ultimately will be approved.

Additional bank loans and concessions from the United Auto Workers union were described by congressional staff members and Wall Street analysts as possible new ingredients in a revised Chrysler plan.

Iacocca, Riccardo's likely successor, is considered more outspoken and a tough combatant. At a news conference last week in Detroit, for example, Iacocca expressed bitterness about Wall Street analysts, news media coverage of Chrysler's problems as well as government reaction.

Talking about the amount of loan guarantees to be sought by Chrysler, Iacocca noted that some government officials had questioned $1 billion. "What would you say to half a billion?" he asked. And he answered that question thus: "I say we should have asked for $2 billion."