On certain vehicles, process precision of the sleeve yoke, which is located at the joint of the rear propeller shaft and the transfer case, is not up to the standard. Because of this, the oil seal may not have sufficient sealing performance, and may cause oil leakage. If left unfixed, the sleeve yoke can become lack of lubricating, and the transfer output shaft or the sleeve yoke may get damaged due to resonance of the shaft in high speed travel. And also, the rear propeller shaft may come off, damaging the fuel tank and causing fuel leakage, and in the worst case, leading to fire.