Internal resistance is defined as the resistance between the molecules of the subject concerned with the study by the means of an external factor that is producing it. In the present work, the internal torsion resistance of shafts is figured out experimentally under an external force which results in deflection. Most of the shaft theories have based their analysis on bending moment, twisting moment or the combined between them. Nevertheless, the dynamic behavior of flexural-torsion coupled vibrations in the rotating shafts is affected by the internal resistance forces due to torsion. The deflected shafts shall be exposed to this resistance. These forces were not considered in any analysis before. The purpose of this work is to estimate the value of the internal torsion resistance in deflected shafts. With the aim of fulfilling this objective, an experimental rig has been constructed to verify the existence of the torsion resistance in deflected shafts and its variation with the rotation angle. As well as, to investigate the spectrum due to misalignment problem. It was found that the deflection in shafts creates resisting torque which is mainly responsible for the spectrum.