Doesn't matters which ever car you drive: be it manual or automatic, transmission fluid plays a significant role in maintaining the transmission and running the engine smoothly. If in case you do not maintain the level of transmission fluid or do not change the transmission fluid regulalry, the gear box is badly affected by it. It spoils the smoothness of the engine and the transmission becomes too hard that its difficult to change the gear from one to another. It also makes grinding noise in the car.