Really there is no earth cable, You have positive and negative, the one that goes to the vehicle chassis, is known as the ground, usually negative, the negative from the battery, would go to the chassis via a short length of cable, one fitting is the battery terminal, the other would be a bolt through an Eye, but for that thickness of cable to need changing, never heard of it, even if the fitting was damaged, put a new fitting on. What is the problem, you are trying to fix.
SD
November 2011