1996 GMC Sierra Trailer Wiring Junction Box 1996 GMC Sierra - Trailer Wiring Junction Box. This Spectro trailer wiring junction box provides a fast, easy way to connect the wires from the trailer connector to the wiring for either a 6 4.8/5(543)Category: Accessories And Parts 1996 GMC Trailer Wiring | etrailer Guaranteed fit 1996 GMC Trailer Wiring. Lowest price guaranteed. Thousands of customer trailer wiring reviews, expert tips and recommendation. Lowest price guaranteed, easy online ordering at etrailer or call 800-298-8924.