Relaxation calculations using natural bond orbitals are carried out for the Puali exchange steric repulsion changes associated with ethane internal rotation using sufficiently extended Dunning correlation-consistent and Gaussian orbitals,so that interpretations are not basis set dependent. These calculations show that the total exchange repulsion is strongly dependent on the C-C bond lengthening that accompanies rotation. The effect of this relaxation is that the total exchange repulsion favors the eclipsed conformer by similar to 6 kcal/mol, far greater than previous estimates obtained without skeletal relaxation. The source of the skeletal flexing dependence stems from the strong dependence of the orthogonalization-induced-energy-shift of the sigma(CH) NBO and carbon core orbitals on RC-C. Strong basis set dependence is found for the pairwise repulsions. Extended basis set calculations attribute an antibarrier energy change to anti/syn repulsions and a barrier-forming one to gauche repulsions. These senses are opposite to the barrier-forming anti/syn CH pairwise interactions found in previous ethane steric considerations.