Weird speedometer issues

Mopar Interiors

  1. indirect_connection

    indirect_connection Well-Known Member

    Messages:
    170
    Likes Received:
    110
    Joined:
    Jun 25, 2018
    Location:
    Memphis, TN
    Local Time:
    12:51 PM
    When I first got my car I checked the speedo with a GPS app and found it to be pretty accurate.

    Shortly after replacing the engine and rebuilding the trans, the speedometer needle started jumping all around. I pulled the cable out of the back of the speedometer and squirted it with silicone spray lube.

    The jumping needle is now an occasional problem, but the rest of the time the speedometer reads steady, but much faster than actual speed. Last weekend I was reading 100mph on the interstate, when I was only going about 70.

    I'm looking to replace the cable, but I can't see how a bad cable could make the speedometer read TOO FAST? Did the bouncing needle kill the speedometer?
     
  2. Scody21

    Scody21 Just send it

    Messages:
    1,793
    Likes Received:
    2093
    Joined:
    Jul 17, 2019
    Location:
    Southwest Washington Coast
    Local Time:
    10:51 AM
    Check the Speedo drive gear in the trans.
     
    • Agree Agree x 3
    • Professor Fate

      Professor Fate Push the button, Max...

      Messages:
      3,541
      Likes Received:
      5169
      Joined:
      Jan 13, 2020
      Location:
      Wisconsin
      Local Time:
      12:51 PM
      ^^This- make sure you clocked the speedo drive correctly when you reinstalled it after the rebuild. If not clocked correctly, it could be "jumping teeth".
       
      • Agree Agree x 3
      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

        Messages:
        54,673
        Likes Received:
        24602
        Joined:
        Oct 14, 2010
        Location:
        Idaho
        Local Time:
        10:51 AM
        All good thoughts, couple more. DO NOT lube the cable with silicone. Use a light grease. Also, make sure the cable jacket is not (for lack of better word) "stressed" --in other words that the jacket "lays" sort of naturally, and of course that it is routed correctly and anchored. "Frays" on the cable or in the jacket can cause problems which only get worse
         
        • Agree Agree x 2
        • Murray

          Murray FABO Gold Member FABO Gold Member

          Messages:
          2,906
          Likes Received:
          2151
          Joined:
          Apr 19, 2010
          Location:
          San Jose, California
          Local Time:
          10:51 AM
          Cables go bad and exhibit some of the problems you are seeing. Check for cable "wrapping".
           
        • 65 Cuda 340

          65 Cuda 340 FABO Gold Member FABO Gold Member

          Messages:
          955
          Likes Received:
          1369
          Joined:
          Dec 27, 2019
          Location:
          Tallahassee Florida
          Local Time:
          1:51 PM
          There is a special speedometer cable lubricant.

          What do you use to lubricate a noisy speedometer cable?

          It should not get into the speedometer head itself, which takes a different lubricant. I can't remember what I used, but the needle is moved magnetically, it is not mechanically geared to the cable as the odometer is.

          Edit: Just checked the factory manual. It says to remove the cable from the housing, and, after lubing the cable, wipe the top foot clean so it doesn't get into the speedometer head, as that can damage it.

          Manual doesn't say anything about lubing the speedometer head (that I could find in a quick look), so I'm guessing Ma Mopar didn't anticipate we'd still be running these things 50-60 years later. Been a while since I lubed a speedo head (and they can get very noisy), but I think maybe I used 3-in-one oil. FWIW
           
          Last edited: Apr 27, 2022
        • 65 Cuda 340

          65 Cuda 340 FABO Gold Member FABO Gold Member

          Messages:
          955
          Likes Received:
          1369
          Joined:
          Dec 27, 2019
          Location:
          Tallahassee Florida
          Local Time:
          1:51 PM
          Note the numbers on the gear housing - clamp it so that the small number slot that corresponds to your gear teeth is at the top.

          Edit: every time I rely on memory I make a mistake. The small number slot should be at the 6 o'clock position, not at the 12 noon position.

          s-l1600.jpg
           
          Last edited: Apr 27, 2022
          • Agree Agree x 1
          • Pentastarnut

            Pentastarnut 67' Barracuda

            Messages:
            1,526
            Likes Received:
            164
            Joined:
            Mar 12, 2010
            Location:
            Abita Springs, LA
            Local Time:
            12:51 PM
            My 67 was doing the exact same thing and also leaking a few drops of trans fluid nightly from the cable housing. I removed and cleaned the housing, changed the seal and O ring and once back together the speedo has been smooth and steady.
             
          • indirect_connection

            indirect_connection Well-Known Member

            Messages:
            170
            Likes Received:
            110
            Joined:
            Jun 25, 2018
            Location:
            Memphis, TN
            Local Time:
            12:51 PM
            I remember clocking the housing when I built the trans using the info in the factory service manual. I no longer remember what color/number of teeth are on the gear though. I'll check the cable routing, I might have repositioned it when I installed the cable for the shifter.
            I'll also try to clean and lube the cable.
            I would just go ahead and buy a replacement cable, but reading through a lot of threads and online reviews saying that the cables listed to fit our cars are incorrect.
             
          1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
            By continuing to use this site, you are consenting to our use of cookies.