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Thread: 411 swap, speedometer jumping

  1. #1
    Potential Tuner
    Join Date
    Jan 2018
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    4

    411 swap, speedometer jumping

    I have a 96 k1500, 5.7 automatic. I recently swapped it to a 411 ecm so that I could tune it. everything works great other than the speedometer. It works intermittently however it has gotten a lot worse over the past week or so. It will drop right to 0 which causes the transmission to downshift to 1st. I have checked a lot of the wiring and cant find any obvious issues. One clue that may or may not be related is the cruise control did not work before the computer swap, but it started working after the swap (when the speedometer decides to work). I have replaced the VSS, but I find it hard to believe that is it anyways considering this started right after the 411 swap. Has anybody ran into any problems like this when swapping ECM's? I am using a 02 express tune on the 411 as it is a 5.7 in the truck. any help would be appreciated. Thanks.
    Last edited by lukepop789; 03-31-2018 at 02:05 PM.

  2. #2
    Yours being a 4x4, the VSS is actually in the TRANSFER CASE. On some, or most?, t-cases there can be TWO different speed sensors fairly close to each other. First, I would verify that you have the correct wiring attached to the correct speed sensor. Then, if that checks out, and you are SURE that the VSS is good, I would replace the pigtail, or electrical connector, for the VSS. We have seen MANY problems with faulty VSS signals as a result of a faulty pigtail/connector.

    Good luck with your repair. Please post back and tell us what you finally figure out that fixes it so that anyone else searching the same/similar problem might find your post and save them a bunch of stress, and headaches.