4L80E Swap Transmission Wire Adapter Harness, VSS Connector

When you put a 4L80E behind an LS in a truck that left the factory with a 4L60E, the transmission bolts up long before the wiring does. The two units do not share a case connector layout, and the 4L80E needs its vehicle speed sensor run separately instead of picking it up the way the 4L60E harness expects. Most people solve that by cutting into the factory harness and butt-splicing, which is exactly the kind of repair that comes back as an intermittent shift complaint two years later. This adapter is the no-splice version of that job.

Part number WATRA30-18 from ICT Billet. It is an 18 inch adapter that sits between the factory transmission harness and the 4L80E case connector, plus a separate vehicle speed sensor connector for the 4L80E VSS. The pin locations are called out on the harness: at the ECU connector, red with a black stripe goes to pin 22 and dark blue with a white stripe goes to pin 23. It is assembled in Wichita, Kansas with USA made OEM grade TXL wire and OEM Delphi connectors, locks, seals and terminals, using the factory wire colors so the harness reads the same as the one it plugs into.

Fitment is GM vehicles originally equipped with an LS series 4L60E, which covers the common donor and swap combinations: LS1, LS6, LM7, LM4, L59, LQ4, LQ9, LR4, L33 and the 4.8 and 5.3 truck engines. Installation goes easier if you route and dress the transmission side wiring before the case goes up into the tunnel, since there is very little room to reach the connector once the trans is stabbed.

Wiring is only half of a 4L80E swap. The controller still has to be told it is driving a 4L80E, so plan on a transmission segment swap in the tune with HP Tuners or equivalent. The adapter gets every connection where it belongs so the tune is the only variable left.