We used Hyperchem to perform molecular mechanics on trans-1,2-dimethylcyclohexane in the less stable conformation, with both groups axial. The result the two methyl groups moved from 180° (in a constrained structure) to 160°, and the strain energy decreased. My working hypothesis is that the reduction in 1,3-diaxial strain was greater than the increase in strain between the two methyl groups. However, I am not sure how one would falsify or to verify this hypothesis. One might use a tert-butyl group to lock the conformation of the cyclohexane ring with two methyl groups forced to be axial, and then one would obtain a crystal structure. Thoughts?