Almost unnoticed amid the sound and the fury over Lebanon and Grenada, a quiet transformation has taken place. Secretary of State George P. Shultz, who three months ago was being written off by many as a loser in the struggle for foreign policy influence, is once again considered a decisionmaking power.
A leading aide describes Mr. Shultz's relationship with President Reagan as ''super.'' Shultz now consults with the President more than ever before, the aide said. The secretary calls Reagan regularly by telephone. He also makes frequent visits to the White House for 15- to 20-minute talks with the President , talks that are often unannounced.
Shultz is also said to work well with Robert C. McFarlane, President Reagan's new national-security adviser. Aides say that Shultz never had a bad word to say for Mr. McFarlane's predecessor, William P. Clark. In fact, Shultz told reporters shortly before McFarlane's appointment that the decisionmaking process was ''working quite satisfactorily'' with Mr. Clark in office. But aides indicate that Shultz is more comfortable having McFarlane, who has much more foreign policy experience than Clark, in the security post.
Shultz's influence is apparent in several moves that have either been decided or are in the making:
* A move to secure greater US-Israeli strategic cooperation, including coordination over Lebanon. Undersecretary of State Lawrence S. Eagleburger is in Jerusalem at the moment working toward this end.
* The likely appointment soon of Donald Rumsfeld to be President Reagan's special Middle East envoy, an appointment advocated by Shultz. He and Mr. Rumsfeld were close associates in the Ford administration.
* The partial lifting of economic sanctions against Poland, expected to be announced shortly. Shultz has long opposed the use of such sanctions. The decision to ease the sanctions against Poland will bring the United States back into line with its leading West European allies. Alliance unity is a goal that Shultz is constantly striving for.
The upturn in influence for Shultz appears to have begun at the White House on Aug. 4 when he met with President Reagan and complained about foreign policy disarray. A State Department official said that Shultz was especially angry over the handling of the major midsummer US military maneuvers in Central America and the Caribbean.
Shultz was involved in early administration debate over the maneuvers and was not opposed to them, the official said. But Shultz felt that the planning process had run out of control. Officials said that the secretary worried about the timing of the maneuvers, the way in which the news leaked and alarmed the Congress, and the way in which the maneuvers clashed with diplomatic moves in the region. The timing of the naval maneuvers off Nicaragua was decided without Shultz's knowledge.
Following Shultz's early August meeting at the White House, he was given greater access to President Reagan and was consulted more regularly with him. He had several talks with the President just before Robert McFarlane's appointment as security adviser.
None of this means that Shultz completely dominates foreign policy. The late October decision on the Grenada invasion was clearly a team effort, with President Reagan obviously playing the leading role. Both Shultz and McFarlane were reported to have advocated the move on Grenada, and were deeply involved in the early stages. But once the President decided to launch the Grenada operation , he turned over much of the authority for it to the Joint Chiefs of Staff. He apparently wanted to avoid a repetition of the abortive Iranian rescue mission of 1980, when President Carter controlled every step of the operation.
Once the invasion was under way, the White House and Defense Department played a much more prominent role in releasing information concerning the action than did the State Department. The press began to speculate about an apparent expansion of the influence of military men within the Reagan administration.
When it comes to other issues, Shultz is again part of a team effort. In the field of arms control, McFarlane appears to be more knowledgeable than the secretary of state. In Central America policy, the State Department seems once again to be playing a major role. But the department has not regained the authority that it held in the days when Thomas O. Enders, now ambassador to Spain, was assistant secretary of state for inter-American affairs. On the Middle East, administration policymakers are divided, as they are at the State Department.
But State Department officials argue that Reagan badly needs Secretary Shultz's skills at this point. Grenada damaged the administration's relations with key European allies. Shultz is an effective diplomatic repairman who has shown that he can heal alliance rifts. One State Department official describes the situation in Central America as a ''mess'' which needs Shultz's management skills.
In East Asia policy, Shultz has played a leading role all along. He and Assistant Secretary of State Paul D. Wolfowitz are top planners for the President's trip this month to Japan and South Korea. Shultz has been heavily involved in getting US-Chinese relations back on track.
But the real test of Shultz's clout may come over Middle East policy. The secretary's advocacy of greater cooperation with Israel on military matters is not likely to be challenged by Mr. Rumsfeld if, as many expect, the latter is named special envoy to the Middle East. Rumsfeld is said by one former associate to have great sympathy for the Israelis. But Shultz's thrust toward greater US-Israeli cooperation is encountering resistance from Secretary of Defense Caspar W. Weinberger, who apparently believes that such enhanced cooperation will damage US relations with Arab nations.
If Israel does agree to play a more active role in coordination with the US in Lebanon, it can also be expected to extract a price. Part of the price demanded is likely to be increased US assistance in building Israel's projected new fighter plane, the Lavi (lion). US Defense Department officials argue that it would be more economical for the Israelis to buy or coproduce an American fighter than it would be for them to develop one of their own. American aircraft producers fear that they will end up having to compete with the Lavi for export sales.