Every Cadillac made in America used to roll down the assembly line past Dennis Foster and 5,000 fellow automobile workers at the aging General Motors assembly plant on Clark Street in Detroit's industrial west side.

But, like so much in the U.S. automobile industry, that has changed. GM has shifted much of its Cadillac production to a modern plant in New Jersey and to its new "robotized" plant at Lake Orion, 25 miles north of here. Another new GM plant known as "Poletown" in nearby Hamtramck will start making Cadillacs next year.

This means that the five-story Clark Street complex, parts of which date to 1902, almost certainly will be phased out. It also means that Foster, who carries the painful memory of a two-year layoff that forced his family onto welfare, is afraid of losing his job again, and with it the $40,000 brick house he calls "my longtime dream."

"Having something, like a job, and then just having it taken away, it hurts. Hurts bad," said Foster, a 32-year-old father of three. "I feel blessed to have my job back . . . . want to keep this job."

Fears such as Foster's are at the heart of the tense negotiations between GM and the United Auto Workers, whose demand for guaranteed job security for 464,000 workers at GM and Ford is the key issue in talks that are expected to end at midnight Friday in a new contract or a nationwide strike against GM.

Both sides portray the talks as the most crucial in the history of the 1.2 million-member union and the industry itself because of the intense pressure of foreign competition and the ever-quickening pace of technology. American industry and the labor movement are watching the Detroit showdown closely, because the patterns set here in wages, concessions and job security are expected to strongly influence labor-management relations in other key sectors.

Officials of UAW Local 22, representing nearly 9,000 Cadillac workers at three Detroit facilities, estimate that only half of them will get jobs at the highly automated Poletown facility, which is unofficially named for the Polish neighborhood from which 3,400 residents were uprooted in a controversial city-supported plan to make way for GM and new jobs.

The specter of job loss caused by automation and corporate reorganization at Cadillac mirrors the concerns of many of the 350,000 GM workers at 151 facilities in 26 states and 90 cities across the United States. The deep fears and anger are evident from the assembly lines to the union halls to the board rooms of Detroit.

Older auto workers worry about living on $935-a-month base pensions, and hope that GM will agree to sizable increases to encourage retirement and make way for younger workers. Middle-aged workers, particularly the "semi-skilled," worry that they will be rendered obsolete by computers, lasers and robots. Young workers are not a major factor because they were the first laid off in the 1979-1982 downturn and the industry has not been hiring recently.

Perhaps the strongest worry for the UAW members, who are paid $12.67 an hour, is the availability of cheaper labor overseas.

The Japanese control 17 percent of the American market -- with projections that their share will double in two years -- but GM, Ford and Chrysler themselves are increasingly turning to "global sourcing," the importation of parts or entire vehicles, not only from Japan, but also from South Korea, Brazil, Taiwan, Haiti, and northern Mexico. Auto workers in some of these places average about $4 a day in wages, according to the UAW.

The dilemma facing UAW President Owen Bieber is that his members are hungry for a job guarantee and a pay increase after a three-year freeze in base wages.

But the harder the push at the bargaining table, the more likely the Big Three car makers will be driven to further "outsourcing," dealing with nonunion and foreign suppliers, industry observers say. A UAW slogan portrays the impact of outsourcing: "When we export jobs, we import welfare" for jobless auto workers.

GM and Ford, enjoying record profits but wary of a downturn, say they must hold the line on labor costs if they are to compete against foreign auto makers for the rest of the century. The UAW, with a 40-year reputation for militance that won pace-setting gains at the bargaining table, is trying to regain clout after agreeing to an unprecedented $5 billion in concessions during the industry's slump.

Here in Detroit, as negotiations wound into the final week at GM's world headquarters, the betting on a strike was about even money.

The steep decline of the auto industry from 1979 to 1982 resulted in an estimated 250,000 layoffs and "givebacks" sought by then-struggling car makers. But the giant firms rebounded with profits of nearly $6 billion last year and paid record, six-figure bonuses to executives.

The rags-to-riches swing in industry fortunes has created a mix of fear and anger among the men and women who build cars, judging from dozens of interviews with workers, UAW officials and industry observers here.

There is fear of more unemployment (estimated at 24 percent among auto workers), but there also is deep anger -- deep enough, for many, to risk a costly strike -- because the now-profitable companies have "taken the money and run" by demanding concessions but refusing to give what the UAW sees as real rewards in return.

"We feel like we were lied to," said Pete Hoover, an auto worker since 1953 and now vice president of UAW's Cadillac Local 22. "The companies begged for concessions, took away pay raises and holidays. Then they raised the price of their cars and split the profits between their top executives and their stockholders. That really galls the guy who works in the pit."

What also galls many workers is the loss of the UAW's power, with its proud image as a "fighting union" that led sit-down strikes and bloody battles in the 1930s under then-President Walter P. Reuther. Those struggles against a union-resistant industry led to breakthroughs such as paid vacations, pensions, cost-of-living allowances and the highest wages of any major union.

But four decades later, Bieber and other UAW leaders face a more complex set of problems than simple employer resistance.

"It is now an industry that plays by international rules," said David E. Cole, director of the University of Michigan's Office for the Study of the Automotive Industry, which receives company and union funding.

Cole said the UAW's leadership is probably as knowledgeable and capable on international issues as the auto manufacturers'.

"They understand this industry, but they have the horrendous task of trying to develop a consensus among the labor movement" so union members will realize that some company demands may be crucial to the survival of the American auto industry, he said.

The UAW's continued emphasis on job security over wages irritates many members, a top union official acknowledged, asking not to be identified. "Bieber is trying to say, 'Look, it's a different world and we've got to adapt. We don't have a monopoly anymore.' But it's hard to say it without sounding like a sellout to the guy who makes $12 an hour and really wants more."

Local 22's Hoover, who has been a union official for 14 years, said the concessionary bargaining created a surge of antiunion sentiment. "It used to be 'us versus them,' the union against the company," he said. "But now, it's become 'us versus them and them,' like it's the auto worker against the company and the union."

Bargaining for job security is highly complex in a global and mobile industry, as the Cadillac example partially illustrates. The often-cited paragraph 96 of the GM-UAW contract, according to the union's interpretation, provides that when GM moves a job elsewhere, the worker is entitled to move with it. But it is not always that simple.

Last year, when GM opened the $500 million Orion plant, with 77 acres of production space under one roof, Cadillac workers were eager to transfer due to Clark Street's projected 50 percent cutback in production. Despite the lack of official announcement, Clark Street is nearing its end.

According to Hoover, although Orion produces the Cadillac DeVille, GM said the Cadillac workers did not have transfer rights, partly because Orion was producing a new front-wheel-drive DeVille different from the rear-wheel models produced at Clark Street. Instead, Orion was staffed mostly by Pontiac workers who lost their jobs in a 1982 plant-closing.

Now, with Poletown ready to open and workers unsure who will get the jobs, there is high anxiety on Clark Street, a decaying neighborhood of boarded storefronts and crumbling streets.

As Dennis Foster waited in the union hall last week for an unemployment check to cover a three-week summer shutdown, an old friend bid farewell by saying, "See you in Poletown, my man."

Foster responded, "I hope so, man. I really hope so."