An improved tractor-trailer communications and tracking system retrofitting assembly, comprising an insulated wire, a flexible wire sleeve, a sealed fuse box, a male connector and a female connector is disclosed. The insulated wire has a length sufficient to at least span the distance between the rear portion of a tractor cab or sleeper box and the power line carrier filter. A first end of the insulated wire terminates in first and second wire segments of roughly equal length. The end portion of the first wire segment has a two-way female connector electrically attached thereto and the second wire segment has a two-way male connector electrically attached thereto. A third wire segment is electrically attached to the female two-way connector at a first end and to the male two-way connector at a second end.