Despite a Reagan administration disclaimer, Federal Reserve Chairman Paul Volcker worries more about the considerable decline of the dollar in the past five months than does Treasury Secretary James A. Baker III. Volcker always has felt that, once a process of pushing the dollar down gets under way, there is the risk that it can go too far.

But the degree of difference has been exaggerated in some accounts of Volcker's statements about the dollar this week. Significantly, Baker has gone out of his way to praise Volcker -- and the performance of the Fed -- and to stress the wide area of agreement at this point between the Treasury and the central bank.

Volcker willingly joined with Baker at the time of the Group of Five meeting last Sept. 22 (among the United States, Britain, Japan, Germany and France) to orchestrate an effort to devalue the dollar, and "up-value" the other major currencies. He also has backed President Reagan's call for a study of how to crank more stability into the international monetary system.

The move to push the dollar off its overvalued perch has been highly successful. Since Sept. 22, the dollar has gone down about 15 percent on the average, for an overall slide of 28 percent from high marks set in February 1985. That is good news, because it should help American industry regain some of its lost competitive edge.

Within the past couple of weeks, even though the five nations no longer are intervening actively to push the dollar down, it has been sliding off at a fast pace -- most dramatically against the Japanese yen. The latest trend has caused something near panic in Japan, where the yen has climbed to about 178 to the dollar, compared with a peak of 262 early last year. (Just since the G-5 meeting on Sept. 22, the dollar has dropped 24.7 percent against the yen.)

Volcker wonders whether this isn't a big enough drop for now. "We could possibly be approaching a danger zone in terms of market psychology," he told the Senate Banking Committee. "We don't want, in effect, to have people wanting to get out of the dollar."

As far back as the October meeting of the International Monetary Fund and World Bank in Seoul -- just a few weeks after the New York meeting of the Group of Five -- Volcker appeared to be nervous about the declining dollar. When you start moving against a currency, you never can be sure how far it will go, he said.

He recalled that, less than a year before, the British were anxious to bring the pound down from what was considered too high a peak. Quickly, Prime Minister Margaret Thatcher's government had a free-falling pound on its hands. By the time sterling had drifted down to $1.05, Thatcher was raising British interest rates to reverse course.

And in Washington, there still is a vivid memory of the altogether-too-successful effort of Jimmy Carter's Treasury secretary, Michael Blumenthal, to "talk the dollar down." Restoring confidence in the dollar then required a savage deflationary effort that resulted in record-high interest rates -- as former West German chancellor Helmut Schmidt once put it, "the highest since Jesus Christ."

So it isn't too surprising to find Volcker testifying that "we have to recognize that depreciation of our currency does not in itself provide any fundamental solution and is, in fact, a two-edged sword." The good "edge" is the expectation that a more reasonable dollar rate eventually will cut the huge trade deficit.

The negative aspect is that the Fed begins to think once more of restrictive money policies.

Another concern over a precipitate drop in the dollar has been best articulated by Stephen Marris of the Institute for International Economics. Marris argues that, at some point, foreign investors -- who in effect have allowed their savings to finance the American budget deficit -- inevitably will get worried, and put their cash elsewhere.

If that happened, the United States would have to boost interest rates to attract enough savings (domestic and foreign combined) to finance the deficit, and the modest economic expansion that is under way could well be reversed. (In his grim scenario, Marris sees the possibility of a global recession.)

Volcker made clear in his testimony that he would be even more worried about the potential inflationary effects of a fast-collapsing dollar -- and perhaps ready to tighten the monetary strings -- if it were not for the fortuitous circumstance of the dramatic collapse in the price of oil from more than $30 a barrel last fall to less than $14 this week.

The effect of the worldwide decline in oil prices is much the same as a huge tax cut: Individuals can spend less money on gasoline and heating oil and more on other goods; and oil-consuming businesses are able to cut their prices. The anti-inflationary effects of an oil-price slide thus will offset the inflationary effects of a dollar decline for some time to come. Significantly, although Volcker freely expressed his worries about the dollar dip, there were no threats of tighter money.

There is certain to be some boost in prices on a huge volume of nonoil imports, and this will relieve the pressure on American manufacturers to keep their own prices low. For example, distributors of a major brand of Japanese cars who paid an average of $8,500 per (equipped) car last September when the yen was in the 240-to-$1 range reportedly will be paying about $10,000 per car with the yen now below 180 to $1.

Even if some of that higher cost is absorbed through competitive pressures, it is obvious that the cost of Japanese cars at the retail level will be greater, especially with restrictive import quotas in force another year.

At the Treasury, it is clear that the policy on the dollar remains unchanged. The assessment is that the decline, although major, has been "steady and smooth," with nothing resembling a free fall, or collapse. As a matter of fact, the judgment is that Volcker's statement itself will have a restraining effect on any speculative assault on the dollar, leaving plenty of room for a further decline.

"In the best of all worlds, everybody would be talking less about the dollar," says an insider. Administration officials agree that the considerable further devaluation they'd like to see would come about best through an expansion of the European and Japanese economies.

But a real danger may be the seductive assumption that international imbalances will fade away once the dollar has found the "right" level. (And who knows what the "right" level is?) The hard reality is that many foreign suppliers took advantage of the overvalued dollar to build a loyal following among American consumers who have enjoyed quality and a freedom of choice as much, if not more, than favorable prices.

American companies are sure to be helped as the dollar comes down and prices of foreign goods increase. But on that "level playing field" that Lee Iacocca and other protectionists have demanded, they still will have to fight for market shares. Today's sophisticated American consumer doesn't look for price before quality.