Interlock mechanism have found multiple uses in the shift system of a manual transmission. It can either be used to block every other rail from moving other then the active shifting rail or it can be used to bring all rails in neutral positions. As a designer the aim is to make systems more compact and efficient in its functionality. This desire to have a compact shift system results in the design of an interlock ball mechanism which allows the use of a single shift finger for two different rails. To validate this design a 5 speed manual transaxle was used, in which the 5th rail and the reverse rail are combined in a single shift finger. Between the rails a single 8mm interlock ball is used to transmit the shifting force to the rails from the shift finger.After a complete analysis of the profile for every degree of gradient the model was manufactured for testing on bench setup established for shifting tests. Various tests were performed and the system was tested and validated. Thus this system helps the designer to make the use of single shift finger for movement on two different rails without the use of a detent mechanism to centralize the rails. This system makes the shift mechanism cheaper, more compact and effective.