Ford Motor Co. borrowed $725 million from banks in the past two weeks as interest rates raced back toward record high levels and car sales continued to fall, the diversified automobile manufacturer has revealed in a prospectus for a finance subsidiary note offering.

The inopportune timing of the fresh borrowings was necessary to help Ford repay $1 billion it borrowed a year ago from its subsidiaries in Britain and West Germany.

At the same time, Ford said more bank borrowing probably will be needed by the end of the year.

Although Ford officials couldn't discuss finances because of the subsidiary registration, analyst David Healy at the Wall Street firm of Drexel Burnham Lambert estimated yesterday that Ford's new bank borrowing needs in the current period will be about $1 billion.

That would indicate that Ford plans to borrow another $275 million in the next three weeks, to continue financing a massive program to reshape the no. 2 U.S. automaker's troubled and unprofitable North American business.

At the same time, however, Ford continues to pay dividends on its common stock, although at a reduced rate.Suffering from record losses and forced into bank borrowings at a level uncommon for Ford, the company paid a dividend of 30 cents a share on Dec. 1, which cost the company $36 million. The current indicated annual dividend rate of $1.20 a share is down from the $3.90 paid in 1979 but still adds up to $144 million a year.

Healy defended this payout policy yesterday, stating it is "relatively small compared with cash flow needs and better in the long run to be maintained." Unless the prime rate continues at levels approaching 20 percent well into 1981, the dividend probably will be kept, he added.

Ford is operating in the red, largely because of unprofitable North American car and truck manufacturing, but overall losses are being reduced. Healy forecast that Ford would have a loss of about $1.50-$2 a share in the current quarter followed by a loss of about $1 a share in the first quarter of 1981 (an overall loss of $120 million). By contrast, in the first nine months of 1980, Ford had a loss of $1.23 billion ($10.20 a share).

The prime rate of banks for short-term loans to such companies as Ford is now 19 percent, and the interest cost per day of the recent borrowings, if made at that rate, would exceed $370,000. Healy said yesterday that although Ford's financial condition continues to be strong, with extensive bank credit lines still unused, the company probably will move soon to restructure long-term financing.

A major problem for Ford is slower-than-anticipated sales of 1981 model cars, unveiled earlier this fall.Ford sales in November were down 14 percent from last year, and the company has started to offer consumers 12 percent loans through dealers and financial institutions for six slow-selling models -- Granada, Mustang, Thunderbird, Mercury Cougar, Capri and Cougar XR-7.

Consumers apparently have been discouraged by the higher price tags on new models as well as higher interest rates for car loans. In the Washington area, for example, car loan rates have jumped from a range of 13 1/2 percent to 14 percent in mid-September to 14 percent to 16 1/2 percent last week, according to a Washington Post survey.

Ford President Donald Peterson said last week that high interest rates may dampen demand for new cars into 1981 and said he has scaled back somewhat his earlier forecast of about 10 million car sales. He did not state a new number, but sales this year are not expected to exceed the 9 million level by much.

Peterson's boss, Ford Chairman Philip Caldwell, differed and said he is sticking with a 10 million sales forecast for the new year. Analyst Healy said yesterday he expects a somewhat better performance, with sales of about 10.75 million cars.

Ford has restored about $1 billion in capital expenditures for the 1981-1984 period worldwide, of $2.5 billion cut out of the budgets during the recession earlier this year. This means that Ford now plans to spend some $4 billion a year over the next four years for plant modernization and retooling for fuel efficient cars.