John Tate has come a long way from shoveling asphalt and driving a garbage truck for the city of Knoxville, Tenn.

In fact, the 229-pound heavyweight boxer now is ensconced in a rented bungalow in this luxurious upper-middle class suburb of Johannesburg where blacks normally are banned from residing under South Africa's system of racial segregation.

But none of Bryanston's residents are complaining because under the canvas of a blue and white striped tent sent up on his backyard tennis court, Tate and his crew -- often to the music of "Cool and the Gang" throbbing from Tate's portable tape recorder -- are training for his heavyweight title bout Saturday against South Africa's "great white hope," Gerrie Coetzee.

This opportunity for Coetzee to replace Muhammad Ali as the World Boxing Association's heavyweight champion represents the South Africans' best chance so far to heal their wounded sports psyche, bruised and jarred by years of increasing isolation in international sports contacts because of domestic race policies.

Because it abrades the isolationist trend in sports, favored by foes of apartheid, the match, arranged by Bob Arum's Top Rank promotions, has generated a storm of controversy. Many black leaders in the States have harshyly criticized the fight and the Rev. Jesse Jackson, chairman of People United to Save Humanity (PUSH), tried in vain to get NBC-TV to cancel its contract to show the fight live.

The World Boxing Council refuses to rank South African boxers and it recognizes Larry Holmes as the world heavy weight champion. Tate, 24, ducks questions about the political implications of the fight.

"I'm not off into politics," he said in an interview in his tent. Asked about his views on South Africa, Tate replied, "They have their good points and they also have a lot of things that need to be corrected. But it's up to the people here to change (the situation)."

Tate, who left grade school early to become a migrant fruit picker, displays none of the panache, sophistication or self-confidence of the famous boxer he may succeed.

"I don't like to say how good I am, that's up to the people to say," remarked Tate, who has a ready laugh that creases his brow and crinkles his eyes.

When interviewers raised the subject of Soweto, the poverty-ridden all-black township across town from where he is living, Tate ventured that "the government needs to do some work there." He immediately turned to Irving Rudd, his diminutive, Brooklyn-born public relations man who sat at his elbow, and inquired, "That was okay to say, wasn't it?"

He was assured it was.

However, Tate was more adamant about other topics, such as Jesse Jackson, who "has his work to do and I've got mine. I get paid for boxing and he gets paid for talking." (Something Arum has said in the past.)

"I don't think he has a right to turn people against us for the work I'm doing . . . I've got to make a living," said Tate.

One night as he jogged in a Johannesburg street, two Afrikaner policemen stopped and asked him for his autograph. And after Tate beat white South African boxer Kallie Knoetze last June in an elimination title fight here, a black domestic servant asked a reporter, "Weren't you glad to see your 'home boy' beat Knoetze? We were." Blacks hate Knoetze because as a policeman he shot a teen-age black boy in the knee, crippling him. The government financially compensated the family in an out-of-court settlement.

But many politically sophisticated blacks view Tate's participation in this fight with disdain because he is helping South Africa break out of its sports isolation. Black South Africans "are going to support Coetzee," wrote a sportswriter in the black weekly, The Voice. "Not that they love him. They believe a traitor is worse than an enemy."

When Tate steps into the ring at Pretoria's Loftus Versfeld Stadium, that in a concession by the government and the rugby team that owns the stadium, that in a concession by the government and the rugby team that owns the stadium will be integrated from the fight date onward, he will bring with him a 21/2-year professional boxing record of 19 wins, 16 by knockouts, and no losses. For boxing aficionados, Tate is an example of how raw, untouched talent can be shaped by boxing "technocrats" into a skillful fighter now ranked No. 1 by the WBA and No.4 by the WBC.

Born Jan. 29, 1955, in Marion City, Ark., Tate was the second of seven children. Much of his childhood was spent without a father since his parents separated and the family then moved to West Memphis, Ark.

His interest in the ring followed several teen-age fights in the streets, the last one leaving him with 27 stitches in his shoulder after his opponent slashed him with a knife and a broken Coke bottle. Tate recounts how "a neighbor said that if I liked fighting that much why didn't I try boxing. So I did."

After some training in West Memphis' Police Athletic League gym, Tate traveled to Memphis, where he worked out in an old movie house and began an amateur record that finally included more than 90 fights. More than 60 were won by knockouts and only nine were lost. In March, 1975, he was a runner-up in the national Golden Gloves tournament, where his present manager, Jerry (Ace) Miller saw him.

Miller bought him a one-way ticket to Knoxville, where he worked days as a truck driver and nights preparing his 6-foot-4 frame in Miller's gym for the 1976 Olympics. Tate boxed his way to a bronze medal in Montreal. He was stopped by Cuba's Teofilo Stevenson, who is regarded as the world's premier amateur heavyweight.

Arum saw Tate's performance at the Olympics and in March, 1977, set him on his professional way with a contract, eventually wheeling and dealing Tate into the Knoetze bout. He won it in eight rounds and thus qualified for next week's championship fight. Arum's contract with Tate extends to three title defenses should ytate beat Coetzee, Arum said. Tate will earn about $500,000 for the fight.