ABSTRACT In this work we apply the Shannon entropy based method to derive a diffusion or instability time in a triaxial model resembling an elliptical galaxy. We succeed in getting an accurate time-scale for diffusion using this novel technique after adopting a particular initial starting space, the one defined by the unperturbed integrals of the system. Comparisons with other standard techniques, such as a least-squares fit on the variance evolution of the integrals and the straight numerical integrations of the equations of motion, are included. The physical results provided in this effort reveal that the role of chaotic motion in triaxial galactic models is almost irrelevant in galactic time-scales, in agreement with previous qualitative approaches to this issue.