The toll of the 1980 recession on the country's vulnerable auto companies is being spelled out this week in their staggering financial losses reported for the three months ending Sept. 30.

Ford Motor Co., Chrysler Corp., and General Motors Corp. performed a version of "can you top this," showing combined losses of $1.7 billion for the third quarter and bringing their losses this year thus far to $3.6 billion. t

An obvious question is, how can a firm such as Ford suffer a loss of $595 million in just three months and still be in business? How can any firm survive such steep losses?

Using Ford as an example, the answer is that its losses, although huge, have not yet reached a critical point, said David Healy, a Wall Street analyst of the auto industry. The banks it borrows from, the suppliers that make its car components, and its investors still believe that Ford's sales will pick up this fall, beginning a gradual recovery. "I don't think they could keep it up much longer, though," said Healy, who is with the firm Drexel Burnham Lambert.

QUESTION: Where did the money go?

ANSWER: Ford was wracked by a three-way whiplash in the third quarter: Its sales were badly hurt by this year's recession and the consumer's rejection of its large cars, and to meet still import competition it has had to make unprecedented investments to chnage over its manufacturing plants to produce smaller cars -- in a hurry.

Ford's working capital plummeted from $1.78 billion on June 30 to $924 million on Sept. 30 in a huge outward flow of cash. By contrast, Ford's working capital at the end of September a year ago was $2.9 billion, more than three times greater than the current figure.

Although Ford's performance last year looked good, it failed to reflect the damage done to the company by inflation, which has pushed up the costs of the new machinery Ford must have to turn out its new models. Accounting rules that took effect this year compel Ford and other corporations to allow for this inflation impact in their financial statements, and that makes the comparison with 1979 even worse.

Q: Then why isn't Ford bankrupt?

A: Because it still has more than $1 billion in cash and marketable securities left. Unlike Chrysler, which reached a point this year where it no longer could pay its suppliers and creditors on time, Ford remains solvent. n

Ford is also still able to borrow money on its own without the Treasury Department's backing. Its deep slump this year has forced it much deeper in debt -- short-term debt as of Sept. 30 had reached $2.2 billion, a 33 percent increase in a year.

According to Healy, Ford has lines of credit exceeding several billion dollars still open, and so long as that situation remains, it can survive.

Q: It's different for companies like Ford than for consumers, then?

A: Not really, said Beverly Welsh of the Financial Accounting Standards Board. A consumer who runs out of money at the end of the week may use a gasoline credit card to fill up the car and, say, a Visa or Master Card to buy a winter coat or new pair of glasses. So long as the consumer doesn't exceed the credit limit on his or her account, charging is no problem. Ford's line of credit gives it the same breathing room.

Q: Who would want to invest in Ford or loan it money?

A: Ford's current creditors have a big stake in the company's recovery. Their hopes are based on Ford's strong position overseas, particularly in Europe and Brazil.

In that respect, Ford is really two separate companies. While its North American division lost $569 million in the third quarter, losses overseas were only $26 million, and industry analysts believe the strength of the company's foreign operations can carry Ford's American business for several years, if the company can break even at home.

Q: If Ford lost $595 million, who were the losers?

A: Ford's third-quarter report wasn't a "loss" in the sense of a stolen wallet or a piece of property that is destroyed.

A great deal of the third-quarter red ink was investment in new, modern production equipment -- robot welders, new car-making tools, more economical production lines. These, in turn, should make it easier for Ford to sell cars this fall and in 1981 by improving its product.

There are losers, of course. Ford has permanently shut down two of its main production facilities, in Los Angeles and Mahwah, N.J., and has put 55,000 employes on indefinite layoff and another 44,000 on temporary layoff. Many of these workers will not be rehired even if Ford's recovery begins this fall.

Investors holding Ford stock have seen the price drop from a high of $37 a share this year to $25 this week. Cash dividends, which hit $1.00 a share in the third quarter of 1979, were only 30 cents a share in this year's third quarter. If the recovery that Ford promises and Wall Street analysts expect has begun, the value of Ford's stock may rise to prerecession levels and in time its shareholders may be whole again.

If the economy rebounds, if Americans return to their old, car-buying habits, if they are more inclined to "b uy American" rather than Japanese, . . . "if these assumptions come true, we will be able to get through this period," says Ford Chairman Philip Caldwell.