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Speedometer Fluctuation

Discussion in 'Early CJ5 and CJ6 Tech' started by Dale Boyd, Oct 18, 2019.

  1. Oct 18, 2019
    Dale Boyd

    Dale Boyd New Member

    Pekin, Indiana
    Jan 8, 2018
    So after getting everything put back together I took it on a test run to the nearest town for about a 30 mile round trip. It ran great and all of the gauges (except fuel) are working now. One odd thing I did notice is that on a level section of highway the speedometer needle is steady. When I get to a hill and give it some gas, the needle starts bouncing +/- 5 mph or so. Anyone have an idea why the speedometer might get squirrely when the engine is under a load?
  2. Oct 18, 2019

    Hellion Banned

    Eastern TN
    Dec 25, 2016
    Well, it's a totally mechanical linkage--a spinning flexible driveshaft in a sleeve from transmission to dashboard. I'd make sure it is well lubricated with a graphite lube and no kinks.
  3. Oct 18, 2019

    PeteL If it wasn't for physics, and law enforcement... 2021 Sponsor 2020 Sponsor

    Hills of NH
    Aug 3, 2003
    Worn or dry inner core on the cable. Possibly one end is slipping from wear or insufficient length, or a loose nut. Occasionally a too-long inner core will also cause needle jump.
  4. Oct 18, 2019

    timgr Eppur si muove. 2021 Sponsor 2020 Sponsor

    Medford Mass USA
    Aug 10, 2003
    When you accelerate or pull a hill or whatever, the motor and transmission strain more against their mounts. This could change the geometry of the cable path and make the cable core rub more inside its sheath. I'd check that your motor mounts and transmission mounts are in good condition. Removing the core from the cable is easy, and you could make sure the ends are tight and straight at each end, with smooth gradual bends. Lubrication is good too - what lube for the cable has come up several times before, and graphite powder is recommended.

    site:earlycj5.com graphite powder for speedometer cable - Bing
  5. Nov 9, 2019

    dieseljeeper New Member

    spanaway, wa
    Mar 7, 2017
    Your speedometer is driven by a cable from the transfer case to the speedometer. Id take a look at your motor and trans mount. It sounds like the engine is rocking over when you put it under a load letting the core rub the housing of the speedo cable

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