In order to overcome the difficulty to properly evaluate the errors resulted from the idealized joint constraint model which is used to simulate the hinge function of joint bearings when performing multibody system dynamic analysis, an effort was presented to quantitate the errors through observation of the changes that the idealized joint constraint model was replaced by a type of more accurate revolute joint model.The dynamic analysis of the luffing process of a gantry crane fourbar linkage arm system was taken as the example to demonstrate the application of the developed models for comparison. Two main joints in the mechanism were provisionally treated as sliding bearing with clearance and the developed revolute models which were different from the idealized joint constraint model included a general vector model, a continuous hybrid contact model and an improved Columb friction model. The effects of joint clearance, contact deformation and friction were comprehensively taken into account in the new model and the system dynamic responses with these two joint models in the same typical working conditions were obtained and compared. The comparison clearly reveals some limits of the idealized joint constraint model, which may provide essential assistance for engineering machinery designers to reasonably use the idealized joint constraint model.