I have a small disc mower (4disc) that i bought second hand and i was told to put gear oil in it at the start of each year which i duly did, it does say Do not overfill where you put in the gear oil but i had no way of telling what level it was at so i filled it until i thought it was safe to use mowing. I am now noticing oil leak ing from the gear casing and i am wondering did i over fill it and busted some seals or something or is that a possibilty.