A new model for the vibronic problem of the luminescence of 3d3 impurity ions in the cubic environment is proposed. The approach developed is based on the numerical quantum-mechanical solution of the dynamic pseudo-Jahn-Teller vibronic problem for the excited states. The spin-orbit splitting of the 4T2 term, and its mixing with 2E, as well as the vibronic interaction with the full-symmetric (A1g) local mode, are taken into account, resulting in the (Γ8+Γ8′+Γ8″) ⊗a1 vibronic problem, and the Γ6⊗ a1 and Γ7⊗a1 adiabatic problems. The effective dipole moment operator is built with due regard for a weak odd-parity trigonal crystal-field component. The vibronic wave-functions are used for the calculation of the band shape of the luminescence in the R line and U band, as well as for the evaluation of the temperature dependence of the lifetime decay emission of Cr3+ ions in CdIn2S4:Cr single crystals. The proposed model provides a very good explanation of the experimental data.