The Tribune Co., the Chicago-based communications conglomerate that owns the Chicago Tribune, the New York Daily News, a variety of broadcast properties and baseball's Chicago Cubs, filed plans with the Securities and Exchange Commission yesterday to make its stock widely available for the first time.

The company, which said it was splitting its 7,393 shares of closely held existing stock 4,800-for-one to make the offering possible, will offer the public 5.5 million shares--about 14 percent of the total--for a maximum price of $26 a share. No date for the offering was set.

The company said 3.4 million of the shares would come from the company treasury and 2.1 million would be made available by certain stockholders to reduce their holdings. The biggest shareholder in the Tribune Co. is a trust held by the family of former owner and publisher Robert R. McCormick, who built the Chicago Tribune into the powerful conservative voice of the Midwest in the middle of the century. The McCormick trust holds about 20 percent of the company's stock; after selling 576,000 shares in the public offering, its holding will be reduced to 16 percent.

The company said it would use the proceeds from the sale to reduce its corporate debt by $50 million and to fund the $21 million purchase of a New Orleans television station.

In making the offering, the Tribune Co. said the financial situation had improved dramatically at the New York Daily News, which had been losing money and which the company had put up for sale in late 1981. It said new union contracts, operating efficiencies and other factors would cut operating expenses by $50 million a year by 1985 and said the paper had had an operating profit of $6.3 million in the first half of this year after a $14 million loss in 1982. "

The Tribune Co. as a whole had first-half profit of $22.7 million on revenues of $758 million, according to the offering statement.

The Tribune Co.'s holdings include newspapers in Florida and California, TV stations in New York, Chicago and Denver, radio stations in New York and Chicago, paper mills and cable television operations in, among other places, Alexandria and Gaithersburg.