4 Wire Trailer Wiring: Amazon This 8 foot 4-wire trailer wiring extension cable was just what the doctor ordered! It connected perfectly to my Motorhome's connector and to the connector on the front of my Jeep Liberty to allow me to have lighting on the Jeep while towing it behind the motorhome. Tips for Installing 4-Pin Trailer Wiring | AxleAddict Jan 18, 2019Buy a 4-pin wiring kit with wires at least twenty feet in length, so it's long enough for your trailer. The most common wire thickness for a trailer is 16 gauge, but I bought thicker wiring for added durability. Depending on the size of your trailer and the number of lights, you might want to check on the Internet for the recommended gauge for your specific trailer.Author: Matt G.