Before removing the terminal from the starter stud look carefully make sure that it's not rusted or corroded or frozen onto the stud. The starter stud is in the direct path of any water from the front tire. So in some cases the stud will have gotten wet and there is the possibility of corrosion or rust problems. If you see that there is rust or corrosion that might have frozen the nut onto the stud, you need to take the proper steps to free it rather than just crank on it with a wrench. Use something like liquid wrench or some other releasing agent to free the nut before trying to remove it.