One of the stars of ''Another 48 HRS.'' talks about getting into the psyche of the characters he plays on screen

As Jack Cates, an unmade bed of a cop, Nick Nolte looks right at home in Another 48 HRS. But compared to the dangerous, and frequently dazzling, career moves he has made in recent years, returning to the role he created eight years earlier was a departure for the hardworking 48-year-old actor.

”It’s an action picture. You get the sh– knocked out of you,” he says. ”Everything gets banged around. I think (Gene) Hackman said the best thing about action-picture acting. You have to be careful how deeply you get into the character, because action pictures, whether or not they’re based on reality, they’re not real. If you’ve worked yourself too deeply into the reality of the character, you’re not going to be able to shoot the gun fifteen times.”

Still, given his notorious penchant for detailed character work — for Down and Out in Beverly Hills he lived as a bum, for Farewell to the King he hid out in the jungle — Nolte could not resist developing a rationale for his cop character’s fanatical pursuit of a drug dealer. While waiting for filming to begin, Nolte recalls that he ”dug through the history of the law in America. Before there was an established police force, problems were dealt with by dueling and whoever won the duel was right. So there’s a tad of Jack Cates, the duelist. The one who walks away is right.”

Director Walter Hill appraises the distance his friend Nolte has traveled between 48 HRS. and its sequel. ”We all have a better idea of who Nick is now than we did in, say, 1982. He’s evolved into a kind of character lead. He’s a formidable actor to be reckoned with.”

With the exception of the waterlogged The Deep (1977), made soon after his breakthrough performance as the boxer-brother in the 1976 TV miniseries Rich Man, Poor Man, Nolte has always shied away from pretty-boy roles. But it wasn’t until he began rooting about in the garbage cans of the rich and famous in 1986’s Down and Out in Beverly Hills that he threw off all the restraints of the heroic, sometimes antiheroic, leading man for grizzlier, more unpredictable parts.

Since then, he’s been working virtually nonstop, playing a put-upon bank robber in Three Fugitives, an obsessive SoHo artist in New York Stories, a World War II deserter gone native in Farewell to the King, a driven private investigator in Everybody Wins, and, most daringly, a brutish New York City cop, the very embodiment of clannish racism and irredeemable evil, in Q&A, this year’s first full-fledged Oscar-caliber performance.

Nolte himself describes the transformation he’s undergone in recent years as a matter of getting back to basics. ”I finally drummed into my head that I really had to get back to the way I’d operated when I was in theater, why I was in this whole acting thing to begin with,” he says. ”It was always to get to the stories that I felt I wanted to tell.”

In the case of Q&A, he explains, he was fascinated ”by the whole subject of racism and ethnic loyalty. I think it’s a part of this country’s makeup. I was very pleased with the film.” For his next project, the film adaptation of Pat Conroy’s novel The Prince of Tides, he was attracted to the character of Tom Wingo, a Southern high-school football coach, because he’s ”a man who has to deal with the women in his life.”

Speaking recently from Beaufort, S. C., where he’s currently rehearsing Tides under Barbra Streisand’s direction, Nolte adds, ”There’s a period in an actor’s life where he’s influenced by the studios, the public, the critics and begins to think he’s got to make decisions based on other things than his insides. So I just returned to the insides, and because I did that I’m going nonstop.”