The slow-motion collapse of the shah's Iran has sent shudders through the principal Middle East oil-producing nations, which had grown used to stability in Tehran and, more grudgingly, to his often maddening regional power pretensions.

with the shah's departure perhaps only a matter of days away, the uncertainities about the future Iran have prompted the United States to dispatch a squadron of F15 jets to Saudi Arabia and more warships to within striking distance of the Persian Gulf and its oil riches.

The flag-showing exercise appears principally dictated by a desire to buck up the weak, basically unstable and underpopulated states and provide them with enough time to deal with Rian, whose new prime minister, Shahpour Bakhtiar, has disowned the shah's gendarme role in the Gulf.

The Arab states -- from Iran's principal oil rival, Saudi Arabia, to the tiny oil emirates and radical Iraq -- should welcome the less imperial Iranian stance. Arab governments were not amused in 1971 when the shah annexed three tiny but strategic Arab islands, Abu Musa and the Greater and Lesser Tumbs, near the arrow Strait of Hormuz through which pass the Gulf's oil exports.

Nor was there unanimity about the use of the shah's expeditionary force in Oman in the early 1970s against the Dhofar rebels. No matter how the conservative arabs disliked those Marxist insurgents, they liked even less the shah's military activism on Arab soil.

Depite a meeting of minds in 1975, Iraq never fully trusted the shah, especially since most of Iran's considerable armor until this day is pointed not against the Soviet Union to the norht, but toward the Iraqi border.

The shah's relentless acquisition of the latest in sophisticated weaponry was also a cause of concern for Iran's Arab neighbors. None believed the Nixon doctrine theseis thatthese arms were designed to defend Iran against Soviet encroachment.

Yet with Iranians seemingly counting themselves out of the regional power game, which was always the shah's personal vision, Abrab neighbors are worried about catching the Iranian disease.

"You do not transmit health; you transmit illness," an observer remarked, noting that on the surface many of Iran's neighbors also suffer from the same waste, corruption, social dislocation and lack of free political expression that combined to bring the shah to grief.

The spillover potential of militant challenge from Shiite Islam in Iran is being watched closely in Iraq, a notoriously unstable country, more than 2k percent of whose citizens are of the same religious persuasion.

Shiite Moslems also account for about 40 percent of Bahrain's population and constitute a sizable minority along Saudi Arabia's oil coast and in Kuwait.

Openly or in private, these Arab states are reexamining their conventional wisdom concerning economic models of development, Persian Gulf defense and the effectiveness of American protection.

Longstanding political assumptions are showing serious signs of strain.

Saudi Arabia charges that the Americans couldn't save the shah, defend the dollar or force Israel to accept easier terms with Egypt. These accusations have been countered by U.S. irritation at Saudi Arabia for going along with last month's 14.5 percent oil price increase, judged excessive by Washington.

Saudi ambivalence toward the United States -- once considered the surest of allies and the monarchy's only reliable bulwark against the shah, the communists or any other potential adversary -- has now surfaced with the suggestion that Riyadh is debating whether to resume diplomatic relations with Moscow, severed in World War II.

Even if such Saudi flirtation with the kind of "godless communism" once anathema in Riyadh is nothing more than a taunting ploy, it does reflect the belated realization that the Soviet Union is a suqerpower.

But beyond these considerations, all Iran's neighbors -- including the Soviet Union with a large Moslem population along its porous southern border -- must be concerned with the possibility that the shah's eventual successors may prove incapable of restoring stability.

However pleased the Arabs may be by Bakhtiar's promises of cutting oil sales to Israel and adopting a pro-Palestinian stand, the present reality is that they openly regret substituting an unknown situation for a man who at the very worst was at least the devil they knew.