Leonard Woodcock has never fit the stereotype of the cigar-chomping, back-slapping labor boss—and not just because he doesn't smoke. In 44 years as a trade unionist he has picked up only two nicknames: "The Professor," for his methodical intellect, and "The Undertaker," for his reserve. Though he is a formidable negotiator, he has never been known as the blithest of spirits. "Let me put it this way," says an associate. "He's not the person you'd choose to sit next to on a long flight to the Coast."

But credentials as a traveling companion are not required for the trip to Peking, and that is where Woodcock seems headed.

President of the 1.4 million-member United Automobile Workers for seven years, Woodcock, 66, passed his union's mandatory retirement age in February. He will step down this week at the UAW's triennial convention in Los Angeles, after which he is the odds-on favorite to be named U.S. envoy to the People's Republic of China. (In the absence of formal diplomatic relations between the U.S. and China, the post carries the rank of ambassador without the title.)

Though he lacks the training and experience of an old China hand, Woodcock is a master of delicate bargaining. Earlier this year President Carter appointed him head of a special commission to Vietnam and Laos seeking information on missing U.S. servicemen. The UAW chief performed with distinction (Hanoi returned the bodies of 11 American airmen and hinted at further cooperation), and the President clearly took notice.

Born in Providence, R.I., Woodcock was the son of a British master machinist who found himself in Germany at the outbreak of World War I and was interned until the fighting ended. Young Leonard and his mother waited out the war in England, where he received his early schooling. The Woodcocks were eventually reunited and made their way back to the U.S.—to Detroit—where Leonard enrolled in what is now Wayne State University. The Depression cut short his student days and sent him to work in a machine shop at 35 cents an hour, 84 hours a week.

Joining a forerunner of the UAW in 1933, he began a long, gradual climb through the ranks. He became first assistant to the UAW president in 1946, a vice-president in 1955 and head negotiator vis-à-vis General Motors in 1958. When the legendary Walter Reuther died in a plane crash in 1970, Woodcock succeeded to the UAW presidency.

A socialist in his younger days, he has maintained his union's traditional commitment not only to bread-and-butter issues but also to broad social reforms. He gets high marks even from adversaries in the auto companies. "He has a temper and a cutting wit," says a GM official, "but he never loses control of himself."

Among the most private of public men, Woodcock has lived alone since he and his wife, Loula, separated in 1963. She lives in California. Their three children (two daughters and a son) are grown, and Woodcock's home is a book-cluttered, 22nd-floor bachelor apartment in downtown Detroit. Some acquaintances find him aloof (no one calls him "Len" or "Lenny") but not rigid. Once a hawk on Vietnam, he changed his mind after heated disagreements with his daughters. "They were so right and I was so wrong," he later confessed ruefully.

Despite a period of deep political estrangement, Woodcock's oldest daughter believes her father is an excellent choice for envoy to China. "He is a self-contained person, and I'm sure he could handle the loneliness of the job," says Mrs. Leslie Tentler, 32, a teacher of labor history at the University of Michigan. "He has values and he's not afraid to be forthright. That's what I respect him for the most. It was the best kind of parenting he could give."