Crankshaft torsional dampers are increasingly being used for the gasoline engines of compact cars as well as for ordinary high speed diesel and gasoline engines. Recently, so-called bending dampers are sometimes attached to the torsional dampers to reduce the bending and axial vibrations.To investigate the influence of such crankshaft torsional and bending dampers on the crankshaft vibrations, we first designed three kinds of dampers, each for the reduction of the crankshaft vibration, in the torsional, axial, and radial directions. Next, we developed two kinds of dampers for the simultaneous reduction in the torsional and axial modes, and in the torsional and radial direction modes. We measured the three-dimensional vibrations for both the dampers and the crankshaft, under engine operating conditions,A four-cylinder in-line diesel engine (4 - ϕ 115 x 110) was used for the experiments. In the series of experiments, we found that, in some cases, only by attaching one simple torsional damper, significant reduction of the axial and bending vibrations could be obtained together with the reduction of torsional vibrations.The effectiveness of the axial dampers and the bending dampers (i.e. radial dampers) was investigated carefully. The coupling behavior of the torsional, axial, and bending vibrations was also investigated for the dampers and the crankshaft.