By using the quasiclassical trajectory method, changes of normal and local mode vibrational excitation energies with time are investigated for XH 4 (X=C, Si, Ge) molecules. The results demonstrate that in a CH 4 molecule the coupling between C--H stretching vibration and H--C--H bending vibration is relatively large so that the energy transfer is fast; while in SiH 4 or GeH 4 molecules this coupling is relatively small and thus an obvious energy relaxation is observed. This implies that there exists approximate local mode vibrations for certain vibrational excitation states.