Dear George,
If he was a Coachman slave, chances are he was from the West Indies or Barbados. They originated from England to that area prior to the states.They mainly grew sugarcane in Barbados,then indigo and rice in Georgetown,SC.I have also read that some slaves were brought to West Indies from West Africa. They were also notoriousfor "willing" slaves to their heirs,thus I believe your ancestors would remain in the same family. Hope this can narrow your search.
Good Luck Jamie