The United Auto Workers union yesterday rejected company appeals to renegotiate the union's current national contracts with General Motors and the Ford Motor Co.

But the union appeared to leave the door open for major contract changes when the current agreements expire next year. The union said it was willing "to start at an early date on preliminary work regarding the 1982 contract." Both GM and Ford are expected to seek economic concessions from the union similar to those the UAW gave the Chrysler Corp.

Using identical language in separate resolutions, the union's GM and Ford bargaining councils said the preliminary work on a new contract "would not include any discussion regarding. . . . reopening the current collective bargaining agreement."

Those union proposals will include demands for job and income guarantees, limitations on the number of nonunion employes the companies may hire, profit sharing and stock ownership for unionized employes, increased worker participation in corporate decision making, and an increased worker voice in the design, pricing and the quality of cars rolling off domestic assembly lines.

The union said there was no justification for reopening the three-year contract with the two companies, nor could a change in the agreement "accomplish what has to be done" to help the depressed domestic auto industry.

But the union also indicated some areas where it may seek major concessions next year from the two auto giants. Specifically, the union said it would demand representation on the corporate boards similar to the representation it now has on the board of the Chrysler Corp. and profit sharing at both companies. GM chairman Roger Smith has indicated he would be willing to consider a profit sharing program for UAW members if the union would abandon cost-of-living provisions in its contract.

GM and Ford spokesmen, reached yesterday in the Detroit area, declined immediate comment on the actions.

UAW President Douglas A. Fraser told a press conference following the council votes that the decisions accurately reflect union rank-and-file attitudes toward contract reopenings designed to yield economic concessions. He said approval by the appropriate council is needed to open contract talks with auto companies, and that the councils' stand means there will be no negotiations with Ford or GM on the current pact.

However, Fraser said he expects the next scheduled round of negotiations in 1982 to be "wide open," especially on the matter of concessions, which GM and Ford say they need to stay competitive here and abroad.

"You obviously have to consider political and economic realities," Fraser said.

Consideration of those realities yielded a near-bankrupt Chrysler $1,068 billion in UAW wage and benefits concessions in three separate contract reopeners since November 1979. Accordingly, GM and Ford officials have suggested through the media and informally in meetings with UAW leaders that they deserve similar dispensation.

But in their resolutions yesterday, the councils rejected that notion.