The purpose of this study is to investigate experimentally the characteristics of rotational, radial, and axial vibration for helical gears with different contact ratios. For this purpose, the gear box is specially designed and manufactured. Two helical gears with different face widths and reduction ratios are investigated. The gear vibration in each direction is measured by accelerometers attached to the gear body. Rotational vibration is the highest and radial vibration is the lowest in the gear frequencies. While the increase of rotational speed increases gear vibration, it does not always increase with torque. It is not also linearly related to the contact ratio. In addition, axial vibration is not proportional to rotational vibration.