Mitsubishi Pajero 91

Hello, I am new to this forum and I present myself, I am Manuel Espinoza and my consultation is the following I have a Mitsubishi Pajero year 91 automatic, and I realized that when walking on the road only four marches enter and the fifth no, the problem is that the engine is expended too much and the expenditure of diesel is demolished, someone could help me in this problem, thank you.

The only solve is to lower the box and make a conflict maintenance with the appropriate master-kit will look good for the problem is that it is expensive