This study is stated that the initial contact pressure by the bolt tightening force is important for the prevention of the leakage in the sealant connection. The maintenance of the initial contact pressure will be able to prevent the leakage of between the front retainer and T/M case for using the sealant and this paper is mentioned the leakage case and discuss the improved case using the parameter study for the contact pressure. The most important factor to maintain the initial contact pressure is the distance between bolts and the second order is the width of face between the bolted distance and next order is the tighten torque. The method to examine the leakage on the driven condition was introduced in this study. The method is the distance between contact parts.