The No. 75 SunEnergy1 Racing Mercedes-AMG GT3 Evo of Jules Gounon led the Repco Bathurst 12 Hour with three hours to go, although the leaders have yet to make a scheduled stop compared to the No. 912 Manthey EMA Porsche 911 GT3 R.
Gounon held a 0.5-second advantage over the No. 77 Craft-Bamboo Racing Mercedes-AMG of Maxi Goetz, with the No. 130 GruppeM Racing Mercedes-AMG of Felipe Fraga in third.
It came after Matt Campbell came in for a routine stop from the lead with three hours and 14 minutes to go after building up a 13-second lead over Gounon.
Campbell charged back to the lead through a second downpour when the leaders pitted to change back on to wet weather tires after a brief spell on slicks.
The Australian lost the lead after receiving a drive-through penalty for having too short of a pit stop, which was initially attempted to be served with a drive-through while under a safety car.
He was later forced to serve the penalty under green flag conditions.
There was drama for the No. 888 Triple Eight Race Engineering Mercedes-AMG of Mikael Grenier, who spun and pitted with apparent damage to the floor of the car.