Transatlantic differences between Paris and Washington once again are the centerpiece at the economic summit conference, but many Europeans are more concerned by the fraying fabric of the once-exemplary relations between Paris and Bonn.

Fruit of a historic reconciliation 20 years ago between neighboring countries that had fought three wars in as many generations, the close partnership between France and West Germany is showing serious signs of strain.

When French president Charles de Gaulle and West German chancellor Konrad Adenauer formally launched their countries on the path of cooperation, even the optimists could not imagine how intricately intertwined their two economies would become.

France and West Germany became each other's best customers--in trade that was not just following the age-old pattern of exchanging French agricultural products for German manufactured goods.

But the lingering economic recession and radically different French and German economic policies are straining the remaining political and diplomatic agreement.

Although both have nominally Socialist governments, France, upon the election last year of President Francois Mitterrand, embarked upon a massive pump-priming operation designed to fight unemployment even at the price of continued high inflation.

West German Chancellor Helmut Schmidt rebuffed Mitterrand's blandishments to reflate and thus pull both economies out of the doldrums, as did the United States, Japan and France's other major trading partners.

Now Bonn is increasingly worried that a go-it-alone France will weaken the bulwarks of European cooperation.

These worries surfaced 10 days ago when the Financial Times of London published a story datelined Bonn suggesting that France was considering not just devaluing the franc--considered virtually a foregone conclusion--but of withdrawing from the European monetary system.

That system, known popularly as the snake, keeps major European currencies--except the British pound--in close relations with each other. The price is constraint on national economic, financial and monetary policies designed to keep all participants' economies generally in line.

Mitterrand did little to allay such fears when he told American correspondents last week that in theory at least he had no firm attachment to the snake although he was hoping for increased international monetary cooperation.

Leaving the snake would allow France to go its own way and work out its own economic salvation. But the price to French-German relations could be incalculable.

The alternative for Mitterrand appears to be admitting he was wrong, at the very least, in pinning so many hopes on an upswing in the world economy last year. Beyond this lie hard austerity measures.

France has a 14 percent inflation rate, three times that of West Germany. It has a growing world trade deficit, especially with Bonn, and is burdened with nationalized money-losing industries.

Oddly enough, Schmidt's West Germany and Mitterrand's France are closer on many policy matters than during the previous seven years.

Initially, Schmidt was concerned about the inclusion of four Communist ministers in the French government, but those fears faded for him. So, too, did concern about a French desire to neglect the special relationship with Bonn in favor of improved relations with Britain.

Such worries disappeared in a shared concern over continuing high U.S. interest rates, the unresolved budget deficit battle between the White House and Congress and the implications for Europe.

If Bonn remains unenthusiastic about hints of French protectionism and a penchant for government rather than private investments, both countries are determined to keep the remnants of detente alive. Thus, they are united in opposing Washington's enthusiasm for conducting economic warfare against Moscow and in limiting East-West trade.