General Motors Corp. and Ford Motor Co. probably will have to rely on local labor contracts with the United Auto Workers union for productivity gains needed to offset the cost of their national agreements with the union, industry analysts and officials said yesterday.

The national contracts -- one ratified at GM and the other tentatively approved at Ford over the weekend -- are relatively modest economic packages compared with some past UAW settlements, the analysts said. But they said that the agreements are still too expensive to reduce the production-cost gap between U.S. and Japanese auto makers.

As a result, the national pacts will have to be paid for with productivity increases. Traditionally, U.S. auto companies have used local labor negotiations to make those kinds of gains, industry officials said.

"What the companies have done in their national agreements is to force the issue of productivity at the local level, much more than they have done in the past" in national contracts with the UAW, said Gary Glaser, an analyst with New York-based Sanford C. Bernstein Inc.

In their contracts, both GM and Ford retained the right to use less-expensive non-UAW sources -- foreign and domestic -- for parts and for completely "built-up" vehicles.

Glaser said that the companies bought that right by agreeing to give 350,000 UAW-represented workers at GM and 114,000 union members at Ford total average pay increases of nearly $12,000 over the next three years.

That translates to about a 2.25 percent first-year increase plus a cost-of-living allowance and a one-time lump-sum payment of about $180. If the cost of living rises 5 percent next year, as most economists predict, the value of the first-year settlement would be approximately 7 percent. Nationally, labor costs this year are averaging about 4 percent.

By retaining "outsourcing" rights, the companies "have the flexibility to do what they will have to do" to remain competitive "if they don't get work-rule and other changes at the local level," Glaser said.

"The focus now clearly will have to be on productivity to recapture the costs of the contracts and to avoid raising car prices," said Harvey Heinbach, an analyst with Merrill Lynch in New York.

But Heinbach said he believes that GM and Ford will get those gains in the local talks without too much trouble. Both management and labor seem aware of what can be lost if the domestic auto industry fails to improve its competitive position, particularly with the Japanese, Heinbach said.

Japanese auto makers are producing cars $1,500 to $2,000 cheaper than comparable models produced by domestic auto companies whose workers are represented by the UAW.

And Japanese manufacturers such as Honda and Nissan -- which are producing cars and trucks in the United States at nonunion plants -- also have a cost advantage over their union-represented domestic rivals, the analysts said.

During negotiations with the UAW in the last three months, both GM and Ford officials said that they would have to negotiate contracts that met their own corporate interests. The implication was that there would be no pattern bargaining -- one company establishing the settlement pattern for the other -- as so often has been the case in the past.

"Of course they said that. But it was all rhetoric," said one analyst, who requested anonymity. That analyst said that the two companies protected their own interests by agreeing to a kind of buy-out pattern -- that is, they were willing to pay higher wages and other benefits in return for the freedom to pursue productivity gains.

GM, the larger and richer of the two companies, set the pattern. "Ford would have liked to have gone its own way, but Ford just didnt't have that kind of leverage," Heinbach said.

"The UAW wanted to return to pattern bargaining" -- which was interrupted during the last recession -- "and the UAW obviously prevailed in its negotiations with Ford," Heinbach said.

But David Healy, an analyst with New York-based Drexel Burnham Lambert, said that Ford probably could afford its agreement -- assuming ratification and subsequent favorable work-rule changes at the local level. (Failure to ratify could lead to a costly strike, which the now-prosperous Ford can ill afford, the analysts say.)

"Ford and GM have similar production cost and pricing structures, and both are making money," Healy said. "I think they can afford similar contracts."

Healy said he doubts that the two agreements will affect wage rates in other industries. "I don't even think that they will have much effect on the auto-related industries," he added.

The auto employment shakeout of the last recession has eroded the influence of the UAW. And the contracts with Ford and GM are designed more to halt that job erosion than they are to set national industrial wage patterns, Healy said.

He said that it is in that light that the UAW is seeking to reopen its current contract with Chrysler Corp. At GM and Ford, the union won novel job-protection measures, such as a job bank to retrain auto workers laid off through automation and other causes.

GM's job bank will cost $1 billion. Ford's will cost $300 million.

The UAW also got Ford to promise that it will continue a moratorium on the closing domestic plants. The plant-closing moratorium was not approved at GM.

For their part, Chrysler Corp. officials yesterday quoted Chrysler Chairman Lee A. Iacocca as saying "a deal is a deal" -- meaning that Chrysler intends to continue its current UAW contract, due to expire Oct. 15, 1985.

"But if the union comes to us" with a reopening proposal, "we would listen to them. Besides, there may be some things that we would like for them to do for us," a Chrysler spokesman said yesterday.