A systematic method of design modification to reduce the influence of the impact in the planar four bar mechanism is developed. For this purpose, an indirect method is used with the objective function selected to be a linear sum $\sum^q_{i=1}Max\mid{\frac{\dot{\gamma}/R}\mid_i$ which is from the Earles and Wucriterion for ever joint with clearance. One coil spring is attached to joint without complete revolution to reduce the undesiable dynamic effects due to clearances at the joints. The design variables are the stiffness of the coil spring and the pre-loading angle. Numerical examples of an offset slide crank mechanism and four bar mechanism considered. To check the suitablity of the object function, the initial and modified mechanisms are compared using the analysis of clearance mechanism to see the difference of dynamic effects due to contact loss and found that the objective function selected is also a good one even for this multi joint clearance problems as well as for the single joint clearance problems.
