Speedometer

Discussion in 'Flat Fender Tech' started by jackdog, Dec 19, 2015.

  1. Dec 19, 2015
    jackdog

    jackdog Member

    Finger Lakes NY
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    Put a D20 t-case in my 51 CJ3A build and when I hooked up the speedometer cable it runs backward. Does the speedometer drive need to be swapped out. If so what replacement is correct. It is also a new speedometer could the problem be there? The t-case is turning clockwise but the speedo needs to turn counter clockwise.
     
  2. Dec 19, 2015
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

    cordele, Ga.
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    D-18 and D-20 turn the same direction for the speedo. If you look at the cable core at the D-20 it will be spinning clockwise but the other end where it screws to the speedo will be CCW. I don't see your problem..
     
  3. Dec 20, 2015
    jackdog

    jackdog Member

    Finger Lakes NY
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    When bench testing the new speedo head it works fine. Put it in the Jeep and the odometer goes backwards and the speed does not register even though the cable is turning the right way. Dug up an old speedo head and installed it and it worked. I am confused. I bought the speedo off ebay and I didn't notice that it was coming from India. Still doesn't explain why it works on the bench and not installed.
     
  4. Dec 20, 2015
    millennium falcon

    millennium falcon Member

    Central PA
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    That is strange.....I swapped my d-20 for a d-18 and my speedo hooked right up and worked great with no mods. I'm interested to see what you find out. Is it possible your only looking at it when you are going backwards? ;)
     
  5. Dec 21, 2015
    sterlclan

    sterlclan Member Sponsor

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    Gotta be the gremlin. Sure you are spinning it the right way on the bench? Seems unlikely that it would change just by being installed. Plus I didn't think odometers would spin backwards.
     
  6. Dec 22, 2015
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

    cordele, Ga.
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    The odometer part is gear driven and it doesn't care cc or ccw. If the speedometer didn't have the stop pin it also would read backwards. Spin the old speedo with your fingers in the direction that makes the needle jump then spin the new one the same direction. What did you find?
     
  7. Dec 23, 2015
    jackdog

    jackdog Member

    Finger Lakes NY
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    Figured it out. The new speedo must be geared high. Jacked up the back of the Jeep and in 3rd gear at higher rpms it went to 10mph. The old one read 40 at the same rpm. Not sure why the odometer was going backward it doesn't now. Maybe I imagined it?
     
  8. Dec 24, 2015
    sterlclan

    sterlclan Member Sponsor

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    if that is so why dont the miles go away in reverse?
     
  9. Dec 27, 2015
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

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    The older odometers would run backwards that is why used car dealers would put a drill and run the mileage back. The feds made the manufactures put a reversing lock on them to stop this but I don't remember the time frame this started. To answer your question sterlclan, I don't think you would notice in just a few hundred feet of backing up. I have a few speedometer heads so I will put a drill on one and see for sure if these jeep one's will indeed back up.
     
  10. Dec 28, 2015
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

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    Just tested 3 early cj5 speedometers and they all rolled backwards on the odometer.
     
  11. Jan 11, 2016
    sterlclan

    sterlclan Member Sponsor

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    well walt i stand corrected... ferris' buddy cameron didnt wait long enough i guess....
     
  12. Jan 12, 2016
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

    cordele, Ga.
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    Well that is the purpose of this forum and we live and learn. This forum is a mountain of info and knowledge from all members. Not all is jeep related which makes it so informative and interesting. The best part is that the members here freely give there time, advice, knowledge, and sometimes even parts, :) so it is a win win place to be.

    FROM A PROUD MEMBER
     

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