Speedometer problem

1971 - 1974 Mopars

  1. Robert Schaad

    Robert Schaad Well-Known Member

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    Started driving my 72 From 7/11 the other night and speedometer started reading about 60 when I was driving about 35. I have already replaced a lot of things as a normal replacement objective. I then jumped on the Freeway and the 120 speedometer went crazy, pegging out, jumping from 80 to above 120. Pulled over and removed the speedometer cable so as not to destroy gauge. Ordered new Speedometer cable. Just another thing I wanted to replace any ways. Replaced, and did not help. Here is the funny point. My car came with a 150 speedometer gauge and when restoring it, I had a 120 that was in a little better condition and put it in. That 120 looked better but was going bad. I put the 150 back in now and works great. Also put new LED dash lights in while replacing Speedometer. Gives a great new look over the old ones.
     
  2. Nacho-RT74

    Nacho-RT74 FBBO Gold Member FBBO Gold Member

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    Speedo is gone... If you check on back of speedo face, will find a coil spring which is the needle return spring. This spring is tensioned by a lever hold by a teflon bushing which also keeps the needle shaft in place. The teflon bushing keeps some pressure over the lever which is also a spring by itself being melted into the speedo housing to keep the pressure over the tension lever. This section is the one what cracks on bushing and gets loosen the return spring.

    It is fixable without dissasemble, but tricky


    7FBC854E-64F1-4891-BAB4-C086620FC662.jpeg
     
    Last edited: Jul 10, 2020
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    • Nacho-RT74

      Nacho-RT74 FBBO Gold Member FBBO Gold Member

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      Here is the fix with epoxy on back. I had to keep the bushing in place with a fork and rubber bands throught the shaft while the epoxy was curing to make the pressure over the tensioner spring lever


      IMG_0474.JPG

      BUT I fixed ( fixed two actually but one of them was also broken into the input shaft assembly ) because it was a km speedo REALLY hard to find. Being in USA the best would be replace it for a good one

      This is the other one I could fix. Note the high beam indicator is an horizontal slot underneath the 120 mark, not the vertical slot like the previous pic which would be in place of the 120 mark

      la-foto-1.jpg

      Then recalibrate it using a drill. 1000 RPMs equals to 60 mph. Made maths to km and using a 550 RPMs drill ( the 1000 RPMs I have doesn't have reverse speed to make spin the speedo correctly )

      With a chrono just checked after 5 minutes running the reading would be the correct one between speedometer and distance

      This was made maybe 30 times to be sure, adjusting more or less the lever tensioner spring to give a more accurate speed reading according with the total distance on a 5 minutes run ( couldn’t more time because the drill got hot )

      843E6EE7-CD0F-4621-8970-7CC0AE29AB55.jpeg 352FEB35-F3DA-4F43-91CC-F1E749189D05.jpeg 64B6942D-44F0-4739-A020-5D69B671E689.jpeg

      Then also attached a decal on red line for better look

      93EFE0EE-BB98-46D8-A178-E3E4A57F47A5.jpeg
       
      Last edited: Jul 10, 2020
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      • 493 Mike

        493 Mike FBBO Gold Member FBBO Gold Member

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        Nice repair! You have to think outside the box due to your location. I salute you sir!
        Mike
         
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        • Nacho-RT74

          Nacho-RT74 FBBO Gold Member FBBO Gold Member

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          Well I must say all Chargers in Venezuela got actually standard cluster. Just in 74 some Coronets called locally Special Editions ( made to replace the New Yorker which on 73 was the last year being assemblied locally ) which are extremelly rare got Rallye clusters, of course in Km along with lot of luxury options. It took me 8 years to get one cluster from one of these being parted out. Two years later found the second one. Just was interested on the speedo because I already had Rallye cluster on my car bought on eBay.

          so, that’s the reason I had to fix these.

          two or three years later I became an extra 150 Miles speedo a friend sent me from USA for free ( it was stuck at the input shaft but could get it spin free ) with a healthy bushing into kilo speedo interchanging the odometer gears and the face. Rest is the same including calibration ( 150 miles is 240 km ) so that’s the one I will use when reassembling my car and storaged the one fixed on a box. Will also storage the 150 miles still on my car.

          Being outside USA spare parts at hands is a must.
           
          Last edited: Jul 10, 2020
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          • Paul_G

            Paul_G Well-Known Member

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            Nice job Nacho.
             
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            • Ron H

              Ron H FBBO Gold Member FBBO Gold Member

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              Yeah Nacho is a genius. He guided me through some wiring for my console with nice-detailed info like he provided in this post.
               
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