The effects of uniaxial stress applied along different crystallographic directions to a cubic system exhibiting the Dynamic Jahn-Teller effect have been studied. E.P.R. measurements were made at 9 Ghz at liquid helium temperatures. Experimental data were obtained as a function of the orientation of the magnetic field and the magnitude and direction of the stress. The observed spectra can be explained by the effective Hamiltonian formulation of Ham and extended by Herrington, Estle and Boatner. The effective Hamiltonian has been further extended to account for the superhyperfine (S. H. F.) interaction with the eight nearest fluorines. Good resolution has been obtained for the S. H. F. interaction in the large stress limit and a method for the determination of the S. H. F, parameters has been proposed.