Torsional frequency calculation

Hello

I am trying to calculate the torsional vibration frequency of a part with a certain torsional moment. In this case, a 60mm steel axle, 100mm long with a mechanism behind equivalent to a moment of inertia of 38kg.m-2. I don't really know how to go about it. I know how to do frequency analysis, but here it gives me the frequency in bending, but not in torsion.

Thank you for your help