Half-centuries from Faf du Plessis and Dean Elgar took the Proteas to 202-3 at lunch, with a 469-run lead over Australia on day four at the Wanderers.
With a 401-run lead at stumps on day three, it was puzzling that the Proteas never declared overnight as the overcast conditions would have suited their bowlers.
Bad light and a slight drizzle interrupted play 25 minutes into the first session, but 10 minutes later, the players walked back out to the middle.
There was no shift in mindset from Elgar, as the Proteas opener continued with his safe approach.
Du Plessis played the role of aggressor, but in the 32nd over, he bundled over in pain. The Proteas skipper took a blow to his right index finger, which he fractured during the India series, off the bowling of Pat Cummins. He received treatment and bravely soldiered on, knowing that he desperately needs a big score.
Du Plessis has struggled throughout the Australia series. His last seven innings scores have been 15, four, nine, two not out, five, 20 and nought, against a side that he averages 45.05 against.
However, he answered his critics by reaching his 18th half-century and fifth against Australia, to take the Proteas past the 150-run mark.
Elgar continued to frustrate supporters. He took 158 balls to reach 39 on day three and only managed his first run of day four after facing 25 balls in the first session and his first run in 70 deliveries. Fifteen balls later, Elgar reached his 12th half-century in 199 balls, having faced 180 dot balls.
The pair took South Africa to 202-3 at the lunch break, having stretched their lead to 469.
The highest successful run chase in history was when the West Indies chased down 418 against Australia in 2003 at the Antigua Recreation Ground in the West Indies.
Australia 221 (1st innings): Tim Paine 62, Usman Khawaja 53, Pat Cummins 50, Vernon Philander 3-30, Kagiso Rabada 3-53, Keshav Maharaj 3-92.
South Africa (2nd innings): Faf du Plessis 81*, Dean Elgar 59*, Pat Cummins 2-39, Nathan Lyon 1-67.
South Africa lead by 469
Photo: Sydney Seshibedi/Gallo Images