In the present paper, the fluid-dynamic forces and the moments acting on a rigid axisymmetric body, which is vibrating in coupled translational and rotational modes, are analyzed by considering turbulent skin friction. In order to test for the validity of the analysis, the stabilities of an axisymmetric body in the various tapered passages are examined theoretically and experimentally. When the flow rate of water is gradually increased, Reynolds number, frequencies and characteristics of the vibrations at stability boundary are measured in detail. In the cases of the divergent passages, the Reynolds number at dynamic instability boundaries caused by the coupled vibrations increase linearly with the increase in the natural frequencies and the slope of the increase is nearly constant independent of the tapered angles of the wall surfaces. Nondimensional critical frequencies are constant values independent of the natural frequencies. Good agreement was obtained, in general, between the theoretical values and experimental results