4L60E to 4L80E swap on a 4x4 truck — complete checklist?

Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.

• Some 4WD 4L80Es lack the output tone ring; in those applications the Quick 4 can use the transfer-case-mounted speed sensor instead, and the manual says to inspect through the sensor opening when tone-ring presence is uncertain. (US Shift)
• In some 4x4 transmissions the output speed sensor may be missing or nonfunctional because the tone ring is absent; the Quick 1 manual says to use a transfer-case speed sensor instead or install a 40-pulse tone ring. (US Shift)
• For 1999-2007 Gen III truck/LS-style harnesses, the 4L60E-to-4L80E conversion guide moves the transmission-connector brown wire from cavity U to cavity S, and repurposes the removed white wire (cavity S) and tan/black wire (cavity T) for the 4L80E input-speed sensor. (Uploads)

Confirm against the instructions for your exact parts before wiring. More: Transmission control in our tuning guide.