President Carter is expected to name former New Orleans mayor Moon Landrieu to be secretary of housing and urban development and to offer the job of secretary of transportation to Neil E. Goldschmidt, the mayor of Portland, Ore., informed sources said yesterday.

The announcement of Landrieu's appointment could come as early as today, the sources said. Landrieu met with the president yesterday and was understood to have accepted the HUD position, succeeding Patricia Roberts Harris, who has been nominated to be secretary of health, education and welfare.

Sources said Carter is scheduled to meet with Goldschmidt today. In Portland, the mayor's office said Goldschmidt had been contacted by Vice President Mondale, asked if he would be interested in the DOT job and had replied that he would like to talk about it.

The White House is searching for a successor to former transportation secretary Brock Adams who, like HEW secretary Joseph A. Califano Jr., was fired by the president last week during a purge of the Cabinet.

Adams already has left his government post, while Califano has remained, pending Harris' confirmation by the Senate.

White House press secretary Jody Powell said yesterday that the process of filling the two vacant Cabinet posts was "moving along" but that Carter had not offered the jobs to anyone. However, Powell spoke before Landrieu met with the president.

Both Landrieu and Goldschmidt were considered for initial appointments in the Carter administration but were passed over for other appointees.

The meetings yesterday with Landrieu and today with Goldschmidt suggested that Carter, as he promised, is moving rapidly to fill the vacancies created by the Cabinet shakeup.

On Wednesday, the president named Paul A. Volcker, president of the New York Federal Reserve Bank, to succeed G. William Miller as chairman of the Fed.

Landrieu's expected appointment and the expected job offer to Goldschmidt also indicated that Carter is moving to strengthen his ties with the nation's mayors. Many of them have expressed disappointment with some of his domestic policies and could be important factors in Carter's drive to win next year's Democratic presidential nomination.

Landrieu, 49, is a former president of the U.S. Conference of Mayors who always has been popular with his fellow urban leaders. Prohibited by law from serving a third successive term as mayor of New Orleans, he left office in 1978 and now is associated with a development firm.

A former New Orleans city councilman, Landrieu handily won election as mayor and remained highly popular through his two terms. As a Louisiana Democrat, he also has ties to such powerful congressional figures as Senate Finance Committee Chairman Russell B. Long (D-La.).

Goldschmidt, 39, is considered a strong administrator and has a solid record of supporting public mass transit, one of the issues on which ousted secretary Adams said the administration was weak.

Portland's present transit system, all buses, is highly regarded by transit professionals as a well-reun operation that has attracted many new riders. Goldschmidt is given credit for providing the political clout necessary to achieve that. CAPTION: Picture, MOON LANDRIEU . . . appointment could come today