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What did you LS swap guys do for a working speedometer?

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

  • LS Control System kit; 4L60 / 4L80: The LS Control System harness is designed to plug into the output speed sensor of 4L60 and 4L80 transmissions, which have a 40-pulse output. (Chevrolet Performance)
  • LS Control System kit; 4L60/4L80 with CP Supermatic Connect and Cruise: The vehicle-speed input is optional, but it must be plugged in when using the CP Supermatic Connect and Cruise transmission control system. (Chevrolet Performance)

Confirm against the instructions for your exact parts before wiring. More: Tach and speedometer signals in our tuning guide.

Confidence: medium — sources disagree or are limited; check the sources below.

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Sources
  1. LS Engine Control System Instructions — Chevrolet Performance