4L60E Internal + External Wiring Harness | Drivetrain Resource The external wiring harness for a 4L60E will need to be spliced into the main wiring harness. It’s not that difficult to do, just make sure that you solder it in and cover it with heat shrink. GM 4L60E Transmission External Wire Harness 1993 and Up 4l60e transmission external wiring harness | eBay www›Search›4l60e transmission external wiring harnessSave 4l60e transmission external wiring harness to get e-mail alerts and updates on your eBay Feed. + Items in search results. 4l60E transmission external wire harness repair 20 pin Rostra 350-0083 41859VC. Brand New. $53. Guaranteed by Fri, Mar. 15. or Best Offer. Free Shipping.