Gear Problem

when on motion after about few kilometer the movement of d vehicle is not smooth then when the gear change it usually make a solid noise as if two iron hit each other.Also want to know the appriopriate place to change the automatic gear oil. In the derch board where u have the all the mitters, there is a place written FUEL DOOR pls what is the meanning. I also notice the vehicle consume excess fuel And the expert here could not solve the problem. Can i also get the mannual