Rotation of wheelset(s) with small mass imbalance can induce relatively large carbody vibration and worsen ride comfort. Since the excitation force due to an imbalanced wheelset is transmitted from bogie to carbody through a traction link, the authors have developed a displacement-dependent rubber bush for traction links, which has a small gap between the rubber and the inner fixture to prevent this excitation. Unit testing of the rubber bushes to check their stiffness and durability, excitation tests using a full-scale test vehicle to verify the vibration isolation performance, and running stability testing with a bogie, have been carried out. A series of running tests on a commercial line were then conducted and the effectiveness of the displacement-dependent rubber bush was confirmed under actual service condition.