Ford Motor Co. reported yesterday that it lost $325.4 million ($2.70 per share) in the third quarter of this year. It was the third straight year the nations's second-largest automaker has reported a third-quarter loss.

And U.S. Steel Corp., the nation's largest steel producer, yesterday reported a $82.4 million loss for the third quarter and said that its steel operations were almost $290 million in the red. The corporation also slashed its quarterly common stock dividend in half, to 25 cents a share.

The last time Ford made a profit in the third quarter, traditionally the auto industry's worst because of costly model changeovers, was 1979 when it made $103 million.

Ford's third-quarter loss last year was $334.5 million ($2.78).

In the second quarter this year, the automaker's profit was $204.9 million.

In the first half of 1982, Ford lost $97.1 million, and so far this year it has lost $422.5 million.

Ford's operating loss for the third quarter this year was $378.4 million, compared with a loss of $479.4 million in the quarter a year ago.

However that loss, tied to the depressed economy particularly in North America, was tempered by increased operating efficiencies and lower foreign currency losses, Ford Chairman Philip Caldwell and President Donald Petersen said.

Ford reported third-quarter sales of $8.05 billion, off 7 percent from $8.66 billion a year earlier.

For the first nine months of 1982, Ford has a loss of $422 million ($3.50) on sales of $27.9 billion. That compares with a nine-month loss last year of $713.8 million ($5.93) on sales of $29.2 billion in 1981.

Operating losses for the 1982 nine months are $204.2 million versus $888.4 million a year ago.

U.S. Steel's loss was the second largest for a three-month period in the corporation's history and a sharp contrast from the profit of $536.9 million in the same period a year earlier. The only bigger loss for the nation's largest steelmaker was the $668.9 million deficit of the final three months of 1979, when it closed 10 plants and portions of six others.

U.S. Steel, which acquired Marathon Oil Co. for $6.3 billion earlier this year, said the loss came on total sales of $4.5 billion, up from sales of $3.5 billion a year ago.

Despite the quarterly loss, U.S. Steel said it earned $1.8 million for the first nine months of the year on sales of $14.6 billion. That compared with earnings of $975.4 million on sales of $10.7 billion a year earlier.

Standard Oil of California, the nation's fourth largest oil concern, based in San Francisco, said its earnings fell 13 percent to $459 million ($1.34 a share), from the year-earlier $527 million ($1.54). Revenue dropped 25 percent to $8.67 billion from $11.5 billion.

For the first nine months of the year, Standard Oil of California's profit was off 47 percent, to $952 million ($2.78), from the $1.81 billion ($5.29) reported for the same period last year. Revenue was off 18 percent to $28.1 billion from $34.4 billion.

Gulf Oil Corp., which ranks as the country's sixth-largest oil concern in terms of revenue, yesterday reported a 54 percent drop in third-quarter profits.

Gulf said from its Pittsburgh headquarters that it earned $146 million (82 cents a share), in the quarter ended Sept. 30, compared with $316 million ($1.63) in the same 1981 quarter. Revenue rose 1 percent to $7.54 billion from $7.44 billion.

Gulf's profit for the first three quarters of 1982 tumbled 33 percent to $623 million ($3.41) from $930 million ($4.77) a year earlier. Revenue was virtually unchanged at an estimated $22.5 billion.

Eastern Airlines reported its deepest nine-month loss in history yesterday. And analysts said the airline was likely to suffer its worst year since it nearly collapsed in 1975.

The carrier lost $87.1 million during the first nine months of this year, the company reported. It also lost $32.8 million during the third quarter.

Eastern's third-quarter 1982 loss of $32.8 million ($1.52 per share), compares with a net loss of $38.7 million ($1.76) during the same period last year.

Eastern's nine-month operating loss of $12.4 million compared favorably to its $20.6-million operating loss during the same period last year.

But its nine-month 1982 net loss of $87.1 million far outstripped the 1981 net loss of $39.2 million.

Sears, Roebuck & Co. yesterday reported its third-quarter net earnings rose 29 percent to $166.7 million (48 cents a share) from year-ago levels.

Sears' revenues for the three months ended Sept. 30 totaled $7.51 billion, a 10 percent increase over the comparable 1981 period.

For the nine months, net income increased 27 percent to $401.8 million ($1.15), including net capital gains and other income of $30.9 million, compared with $115.2 million a year earlier. Nine-month revenues rose 9.4 percent from a year earlier to $21.15 billion.

Xerox Corp., citing the weak economy and competitive pressures that forced down prices, said yesterday its third-quarter profit tumbled 39 percent from a year earlier as revenue rose 3 percent.

In the latest quarter, profit fell to $99.1 million ($1.17 a share), from $63.1 million ($1.93) a year earlier. Revenue climbed to $2.13 billion from $2.08 billion.

For the first nine months, earnings were off 24 percent to $370 million ($.37) from $485.5 million ($5.75) in the comparable 1981 period. Nine-month revenue slipped to $6.24 billion from $6.28 billion.