The Teamsters union said last night that it has reached a tentative three-year contract settlement with two major trucking company groups and that it anticipates no strikes as it continues negotiations with hundreds of smaller firms.

The settlement was announced hours before the Teamsters' master freight contract expired.

But Teamster sources said that scores of regional trucking companies around the country are balking at the settlements accepted by the larger groups and that some of them could be hit with "selective strikes."

"No strikes are contemplated at this time," Teamster spokesman Duke Zeller said late yesterday. He said talks will continue with firms employing about 20,000 drivers not covered in the two larger settlements. About 200,000 are covered overall by the national Teamster contract.

Contract terms were not disclosed, but Teamster President Jackie Presser hailed the agreement. Presser said it contains "impressive wage increases and meaningful job-security protection."

The Teamsters have scheduled an effort beginning Wednesday in Chicago to persuade local officials and rank-and-file Teamsters to accept the pact. In 1983, the rank-and-file overwhelmingly rejected concessions Presser had backed.

Presser stressed that the agreement contains "no two-tier wage structures, as had been indicated by misinformed sources early on." He was referring to an industry demand for a permanent lower pay scale for new hires, substantially below the $13.26 hourly average.

But union and company sources confirmed yesterday that the agreement will start new workers at lower wages, gradually increasing their pay until they catch up to the veterans' pay scale after several years.

"It is a form of two-tier pay system, and Jackie's denial of it is a matter of semantics," said a spokesman for Teamsters for a Democratic Union, a dissident, Detroit-based union group.

The union has kept a tight lid on negotiations, largely because Presser and other officials feel that premature disclosure of some terms could fuel opposition to the contract, which will take about a month to approve by mail ballots. Presser's proposed 1983 concessions were defeated by an 85 percent vote.

"Double-breasting" -- the setting up of nonunion subsidiaries by union firms -- was a crucial issue in the 10 weeks of negotiations, and Presser's statement yesterday said new contract language contained "the biggest strides yet . . . in stopping double-breasting or diversion of freight" to nonunion firms.

The current contract contains language on this subject, but that has not deterred dozens of union firms from setting up nonunion subsidiaries through holding companies.

Arthur H. Bunte, president of Trucking Management Inc., which represents 35 of the largest firms employing a total of nearly 100,000 Teamsters, declined to comment on the new pact pending ratification by the union and Trucking Management members.

A second industry bargaining group, the Motor Carrier Labor Advisory Council in Chicago, also announced tentative acceptance of the same agreement, but a third trucking group, Regional Carriers Inc. of Kansas City, has not yet settled and is continuing negotiations.

The current negotiations were the most fragmented in the 20-year history of the national Teamster contract, with hundreds of struggling firms demanding separate terms.

Deregulation of trucking has allowed the growth of thousands of nonunion firms and has forced hundreds of unionized firms out of business.

More than 100,000 Teamsters have lost jobs since deregulation of the trucking industry, prompting intense concerns about job security.

Wages and benefits also were major issues in the talks because drivers have not had a raise since 1982 and pensions have been frozen for six years.

Presser said "new and innovative contract language" will help thwart "abuses" such as the growing use of temporary drivers who do not receive full union benefits.