There's a few things I'd want to know first. Does the wire smoke at the connection, but the cable stays cool?? (bad ground) Is the wire getting hot?? (short in starter) If the cable stays cool and you ensure the ground is taken care of next i'd be ruling things out. One guy thought it might have been the solenoid. Well, put your truck in neutral, turn the key to the on position (but don't start) and under the hood, bypass the solenoid with a screwdriver or a thick piece of cable by jumping the big wires. (that's your 12v from the batter to the starter, the little ones go to your starter switch). It sounds more to me like it's going to be a bad starter.
