Two-time US Open champion DeChambeau carded a six under-par 65 for a tournament total of 14 under-par, two shots ahead of David Puig (64) and home favourite Brandon Grace (66).
It was another low-scoring round on the Jack Nicklaus-designed par 71 course, where there are expected to be more than 100,000 spectators during the four days, as DeChambeau carded an eagle and seven birdies, but also a double bogey on the par-four 12th.
Southern Guards (34 under-par), made up of the South African quartet of Louis Oosthuizen, Dean Burmester, Grace and Charl Schwartzel and roared on by the home crowd, led the team competition after the first round, but were toppled from the top by Torque, who have a combined score of 36 under-par.