4 gauge wire is too small, 2 gauge is the absolute smallest and what is used for the winch power cables. However, I'd bump that up one gauge larger to compensate for the longer run's added electrical resistance. And it's not the alternator that provides the winch's big amperage it draws, it's the battery. No alternator made for Jeeps can put out more than maybe 30-40% than what a loaded winch can draw.
