The leadership of American labor is going through the rites of generational torch-passing, and nowhere is the struggle causing more turmoil than among the 1.4 million members of the United Steelworkers, who will vote Tuesday to select a new president.

At stake is control of the AFL-CIO's largest union, and there are signs that the policies, politics and cohesion of the entire 14-million-member federation itself will be affected as power passes to younger leaders from those who rose out of the labor struggles of the 1930s.

The race to succeed retiring USW President I.W. Abel, 68, pits Edward Sadlowski, a 38-year-old insurgent and tough-talking advocate of a return to union militancy, against Lloyd McBride, 60, the candidate of the union's "official family" and proud protector of its reputation as contract pacesetter for labor.

For all practical purposes, it also pits Sadlowski, director since 1974 of the union's huge Chicago-Gary district, against most of the elders who dominate the AFL-CIO.

Abel, whom Sadlowski has made the focal point of his attack, is openly campaigning for McBride, a union staff member since 1940 and head of its St. Louis district. Federation president George Meany dropped all pretense of official neutrality last month in attacking "so-called limousine liberals" and other "outsiders" who dared "meddle" in union business on Sadowski's behalf.

Against this backdrop, Sadlowski has become something of a media celebrity, inspiring reams of colorful words about the brash young David taking aim at the stodgy old Goliath.

The romantic characterization is part of a problem that has caused McBride to hire a public relations firm, but it oversimplifies the case.

Sadlowski - "Oilcan Eddie" among friends - has been called charismatic, spiritual heir to the early labor heroes, burly, brawling, boyish, brainy and a good guy to belly up to the bar with. McBride usually comes out as paunchy, dull and balding.

McBride invites invidious comparisions by wearing grey business suits and color-coordinated ties, while Sadlowski goes around in open-necked shirts and leisure suits. McBride's friends in the union hierarchy lend support to Sadlowski's charges of machine bossism by wading in massively, not subtly, on McBride's behalf.

Sadlowski, who won his Chicago Gary office in a government-run election after the Labor Department found irregularities in the first vote, accuses the union leadership of undemocratic practices and an unduly cozy relationship with management to promote increased productivity. The Abel-McBride forces dismiss the charges as examples of rhetorical excess by Sadlowski.

His knock-the-bosses campaign is attracting financial support from liberal circles outside the union as well as tapping a rich vein of frustration and anti-establishment feeling among many steal workers.

One of his problems is that the steel contract is the envy of many other trade unionists, with hourly pay of roughly $8, cost of living increases, generous pension, medical and vacation provisions for up to 84 per cent of pay for two weeks during any energy-caused layoff.

And though the USW is not a model of union democracy, with the president wielding enormous appointive powers and its internal elections scarred by occasional fraud, even its critics concede that corruptions not an issue.

Indeed, the fact that it is one of the few large industrial unions to choose top officers by members' secret ballot rather than convention is one reason Sadlowski has a chance.

The impact of a Sadlowski victory on labor as a whole is unclear, although Meany's press releases, a threat by Abel to resign early if Sadlowski wins, and the continuing flurry of dire rhetoric from the Abel-McBride camp conjure up a vision of Armageddon.

One major result, some observers say, would be the loss to Meany of his strongest ally, who sits at his elbow at the AFL-CIO executive council table, in exchange for a rebel who has personally attacked him.

Some suggest Sadlowski's election would reinforce more liberal minority forces within union leadership ranks, especially if the United Auto Workers, which left the AFL-CIO in a policy clash with Meany nine years ago, returns to the fold, as it may do later this year. The federation's hawkish stand on foreign policy might be tempered, although most observers see less change in domestic policy, especially on the bread-and-butter economic issues that head labor's legislative agenda.

There would probably also be more ferment, more challenges to entrenched leadership patterns, some say. "There may be a lot of little Sadlowskis running around in other unions who would get ideas," said Clyde Summers, professor of labor law at the University of Pennsylvania.

Another result would probably be the demise of the steelworkers' highly publicized "no-strike" agreement of 1973. This was designed to end a boom-bust cycle in which the steel industry raced to stockpile output in advance of a strike, including buying abroad, and then laid off workers in slowdowns afterward. Unresolved disputes are now sent to arbitration.

Sadlowski has made a major issue of the agreement, charging it gives away the union's best bargaining chip and should have been submitted to a rank-and-file vote - a step he also advocates for contract ratification instead of the present system of approval by elected representatives.

McBride says the agreement produced the best contract the union ever had, including a 35 per cent incease over three years along with a $150 one-time bonus and guaranteed improvements for the next contract. But he says he, too, would scrap it if the contract to be negotiated this year goes to arbitration.

The election comes at a time of transition for the Whole American labor movement, when George Meany's generation is relinquishing power - generally but not always to trusted leutenants. There has always been change, probaby more than people realize because of the dominance of the durable Meany, but the pace is quickening.

Meany himself, at age 82, will be stepping down soon, probably to be succeeded by secretary-treasurer Lane Kirkland, a 54-year-old former sailor from South Carolina who is not expected to wield the personal clout that Meany has in his 25 years as federation president.

In the 1.4-million-member United Auto Workers, a smooth transition is expected between retiring president Leonard Woodcock and his successor, Douglas Fraser, both in their 60s and both proteges of the late UAW President Walter Reuther. But, significantly, age restrictions decree that they will be the last of the Reuther generation to lead the nation's second largest union.

The International Association of Machinists is expected to get a new, more liberal president in William Winpisinger; presidency of the dissention-wracked, reformer-led United Mine Workers is at stake in an election later this year; transitions are under way among operating engineers, textile workers and other unions.

One telling fact is that at least eight of the 35 members of the AFL-CIO's executive council will not be back next year, most of them victims of age. By next year, only two members will be served for more than eight years.

"It's more of a generational change than an ideological change," said a close observer, "but when you put it all together with Meany's departure, the return of the UAW, the Sadlowski challenge regardless of who wins, you create a different climate. Some ways of doing things are bound to change."

Sadlowski is generally regarded as a long shot, at least in labor circles, although predictions are risky for elections in the steelworkers union - a giant conglomerate of 5,400 U.S. and Canadian locals embracing steel, aluminum, container, chemical and construction industries as well as grocery stores, cemeteries and even mushroom farms.

Basic steel workers, who are expected to give Sadlowski his strongest support, constitute only about one-third of the members but often rally strongly behind insurgencies.

Challenges are nothing new in the steelworkers. Abel himself ousted President David J. McDonald on a charge of "tuxedo unionism" in 1965, although that was more of an internal struggle within the existing leadership than an insurgent's attack on the establishment.

Just as Sadlowski cites McBride's support from other union officials as an example of undemocratic practices, Abel and McBride charged that "outside" forces backing Sadlowski - Washington lawyer Joseph L. Rauh, retired UAW official Victor Reuther (brother of Walter) and economist John Kenneth Galbraith, among others - have their own ulterior political motives.

Said Rauh: "Abel never minded outsiders till Sadlowski got 'em all." Rauh said he contributed to Abel's 1965 race for USW president and Abel cashed the check. Society as a whole does have a stake in the election. Rauh contends, arguing that if Abel hadn't backed Meany in supporting the Vietnam war in the 1960s, the Johnson administration wouldn't have had the political backing to escalate the war.

"The war," retorts a leading USW official, "is over."

With each side expected to spend at least $300,000 on the campaign, financing has become a key issue.

McBride accused Sadlowski of getting most of his money from outside the union, including employers. Sadlowski denies this and says well-paid union officials (Abel is paid $75,000 a year, about average for presidents of a big union; Sadlowski himself gets $35,000) and the union's 850 staff members are financing McBride's campaign.

Although the votes will be counted and reported within 10 days of Tuesday's voting, it may be a longtime before the election is decided if the vote is close. Sadlowski's troops, remembering the voting irregularities in his district election, are poised to spot fraud and can be expected to challenge anything questionable if he loses narrowly. The Labor Department is providing some assistance but not direct surpervision of the balloting.

Moreover, negotiations for a new contract are scheduled to being later this month. They might have to be delayed, or be conducted while the leadership, and its stand on the crucial "no-strike" provision, is still in doubt.

"That," said a USW official, "would be a helluva way to have to negotiate a contract."