Question
My tree has bark that is black about 15ft up the trunk. There are multiple woodpecker holes and ants in the holes and on the bark. The leaves look normal.  I checked oak trees nearby and no others have black bark. This tree was slightly damaged during a hurricane a couple years back. It took over a year for leaves to grow back completely. Don't want to leave it if a disease will cause it to break easily in wind as we are fairly close to the gulf.

Answer
The presence of woodpecker holes could indicate that insects have moved into the tissue of your tree. The ants are most likely attracted to the 'honeydew' or sap that these holes have exposed. Insects and other pathogens(fungus, bacteria) are attracted to stressed or decaying plant material, which leads me to believe the black you're seeing could indicate the presence of a fungus. The damage this tree faced could have made a direct entry-way for pathogens to move in and infect your Oak. It sounds as though this tree is under intense stress since it took it that long to re-leaf. The inside tissue of this tree is most likely decaying and I would advise removing the tree if it is close to any buildings.