Teamsters union President Jackie Presser, seeking acceptance of his tentative three-year national trucking agreement, made a sales pitch to 600 union officials yesterday in Chicago amid signs of members' growing opposition to proposed concessions for major companies.

The contract provides wage increases averaging 3.5 to 4 percent yearly and improves pension and health coverage, but it eliminates additional cost-of-living allowances and cuts pay substantially for new hires and for part-timers, according to union and industry sources.

"We think this is a really good contract that satisfies our members on the three main areas they were concerned with: health, welfare and pension benefits; job security, and wages," said Teamsters spokesman Duke Zeller.

Zeller said he was "not aware of any concessions" affecting current drivers among the 200,000 covered by the National Master Freight Agreement.

But a spokesman for Teamsters for a Democratic Union (TDU) in Detroit said many drivers fear that the lower pay rates for new drivers and for part-time or "casual" workers will result in increasing use of these lower-wage employes and will eventually cost thousands of jobs.

"These terms also increase the competitive advantage to the larger carriers, and that will drive smaller carriers out of business, and cost us more jobs," said Rick Smith, a spokesman for TDU, a union reform group. "This will be a very hot issue as more locals learn about it."

An industry source said the contract contains safeguards intended to prevent laying off full-timers to hire lower-wage replacements.

"Double-breasting" -- the creation of nonunion subsidiaries by union firms -- is a major job-security concern for the Teamsters, but it was not known what new protections, if any, the agreement contains.

Voting on the contract will be conducted by mail balloting expected to take about a month.

Presser, who is handling his first nationwide trucking contract as head of the 1.9-million-member union, lost by an overwhelming margin when he proposed midterm contract concessions in 1983.

The Teamsters distributed a nine-page financial summary of the new contract yesterday, but were not able to give copies to the 600 local officials in Chicago "because there was no way it could have been printed and prepared in time," Zeller said.

A TDU official said that conducting the Chicago meeting without distributing the proposed contract "is undemocratic and conveys the sense that there is something hidden in the contract that can not stand the scrutiny of an educated membership."

He said TDU might challenge the process in court.

Veteran Teamsters earn about $13.50 hourly and would receive increases to about $15 by the third year of the contract.

New drivers would start at about $9.50, although their pay would rise to equal the veterans' scale by 1988.

Part-timers would be paid $11 to $12 but receive no benefits.

More than 100,000 Teamsters have lost jobs since the federal government deregulated trucking in 1980, fostering the growth of thousands of lower-cost nonunion operators. Hundreds of unionized firms with total revenues of more than $3 billion were put out of business by competition from these new operators and from railroads.

The contract has been tentatively approved by the two largest industry bargaining groups, Trucking Management Inc. and the Motor Carriers Labor Advisory Council. But hundreds of smaller firms, many saying they will be driven out of business by higher costs, are balking at the master agreement.

Zeller said no strikes are contemplated until the union sees how many firms agree to the terms of the master contract.