Pushing back the Social Security retirement age from 65 to 68 by the year 2000, as a House subcommittee proposed to do last week, would occur so far in the future that its impact on workers and employers is unclear, according to a survey of personnel specialists and pension analysts.

"If Congress were to vote the change effective tomorrow, there would be a traumatic impact on workers and their expectations and morale, as well as a whole lot of adjusting on the part of companies who anticipate most of their workers will retire at age 65 or earlier," said the personnel director of a major U.S. utility.

"But because the change occurs so gradually and far in the future, there will be a slow adaption on the part of both. What those adaptions will be is not totally predictable today, although clearly the average worker will retire later," he said.

Nevertheless, experts identified a number of likely results of a shift in the retirement age to 68, including:

Difficulties in advancing younger workers as older employes stay on the job longer.

Increased suffering for many workers who retire, often early, because of ill health or because they cannot find an adequate job.

Reduced pension costs for private employers, who will not have to pay benefits as long. That savings will be offset somewhat by the higher costs associated with employing older workers, such as bigger insurance premiums.

The subcommittee action, which is a far cry from full congressional approval and presidential signature, was taken to help ensure that the Social Security system does not go bankrupt in the early part of the 21st century. It does not speak to the system's expected rocky performance over the next few years. Other congressional actions must deal with that.

By 2010, the earliest of the babies born in the years immediately following World War II will be nearing retirement age. Within a decade after 2010, the by-then aged members of the baby boom of the 1940s and 1950s would threaten to swamp the retirement system if some changes are not made.

There would be too many individuals receiving Social Security benefits relative to the number of workers paying taxes into the system. The House subcommittee action is an attempt both to keep individuals paying taxes longer and drawing benefits for a shorter period.

Employers worry that a later retirement age will make it harder to move younger employes up in the ranks. That could affect both employe morale and productivity. "Workers who expect to get Joe's job when he retires at 65 will find they have to wait until Joe is 68," said one personnel chief.

However, he said, because the retirement-age increase will be phased in over 10 years (between 1990 and 2000, under the subcommittee bill, the age would slide from 65 to 68) worker expectations will change slowly. "It may or may not be a problem," he said.

Joseph Famularo, senior vice president for personnel relations at McGraw-Hill Inc. said that while promotion bottlenecks might be a problem in some traditional industries, they will not be in many others. "Jobs have a way of changing so much," especially in newer industries like data processing, said Famularo, that there is much less "waiting in line" than in the past. Furthermore, he said, there used to be few jobs at the top but in recent years there has been a tremendous shift into higher level jobs.

Whether productivity will be affected depends on worker performance. "What's the difference between 65 and 68?" asked Don Harrington, director of benefit planning for American Telephone and Telegraph Co. "I don't know in terms of job performance? There's some concern. If it is true generally (that job performance suffers between 65 and 68), it hurts you. But if it's not true, it doesn't make much difference."

In many industries, such as steel and autos, where the private pensions are so attractive, the current Social Security retirement age seems to have little bearing on the decision to leave the work force. In these industries, for example, workers retire, on average, before the age of 60.

Even in industries where pension benefits are not so good, workers are deciding to retire before 65. Larry Smedley, associate director of the Social Security department of the AFL-CIO, said that 60 percent of all workers retire before the age of 65. The subcommittee bill would still permit workers to retire at age 62, but the retiree could collect only 64 percent of the benefits that would be available at age 68. At age 65 under the bill, the worker would be eligible for 80 percent.

The workers that would be hurt most, Smedley said, are those in industries that have "less adequate or no private-pension protection" yet still have to retire. He said surveys have shown that 50 percent of workers who retire before the age of 65 today do so for reasons of ill health, or because they cannot find an adequate job.

"Those people exist, there is no doubt. But they can be taken care of in other ways, rather than through a system that permits open-ended yearly retirement," said one top corporate official.

Smedley said the many union-negotiated pension plans that have their early retirement provisions keyed to a Social Security payout will be hit, too, if Social Security benefits available at age 62 are sharply reduced. "These plans have to fund themselves 30 years in advance," Smedley said.

He said there will be many collective bargaining problems with such a change.

Private pension plans, most of which pay benefits designed to be coupled with Social Security payouts, may incur lower costs if workers, on average, push back their retirement ages, according to John Feldtmose, vice president of the benefit consulting firm, Johnson & Higgins.

If a worker retires at age 65, the benefits are paid out for an average of 15 to 17 years, Feldtmose said. If the age moves back to 68, three years will be knocked off. That could save companies as much as 25 percent.

However, he noted, if workers are on the job longer there will be higher employment costs. In addition, most private pension plans do not give employes more pension credits if they work beyond age 65 (under current law, non-executive workers cannot be forced to retire until the age of 70). If the Social Security retirement age is pushed back to 68, companies probably will give pension credits until 68, he said.

Even with those off-setting higher costs, Feldtmose said, companies should save about 10 to 12 percent of their pension costs.

The one group that will not be affected much by a change in the age at which retirees are eligible for full Social Security benefits is the executive. "Social Security benefits to him are unimportant," according to Bob Callan, a partner in the executive recruiting firm McFeely Wackerle Associates.

Executives are the one group that, under federal law, can be forced to retire at age 65, and at many companies 65 is the mandatory retirement age for executives.