Speedometer conversion

WINST10WINST10 Posts: 24Member
Hi everybody!  I have a '51 Pacemaker sedan and I've been having some problems with my speedometer.  The speedo did not work when I bought the car and I've spent quite a bit of time messing around with it.  I tested the head unit by spinning the input shaft with my fingers and also connected it to a cordless drill.  The needle will move when I do this so I believe the head unit is okay. 

I replaced the speedo cable and the pinion gear.  The speedometer worked for a short distance (less than one mile), then stopped working completely.  I believe there may be a problem with the gear inside the transmission that drives the pinion gear.

I am considering giving up on the stock setup and converting the speedometer to a GPS controlled unit.  I would like to use a GPS unit with a mechanical output to drive the stock speedometer.  I found some information about a unit called the Speedbox.  Does anyone have any experience with this unit or something similar?  Thanks for your help!  


  • railknightrailknight Posts: 460Expert Adviser
    You probably did this, but just in case, don't overlook lubricating the speedometer cable with a graphite grease or what worked for me, Lock-Ease graphite oil.  Made a difference when my Super Wasp speedometer gave up completely.  Took the cable completely out, cleaned it and coated it with Lock-Ease and that brought the speedometer back to life with no more issues.  Also, for 1948-54 models there's an oil hole and wick to lubricate the speedometer pointer in the back of the instrument.  Make sure you oil that with a few drops of or equivalent to S.A.E. 10 oil.   
  • GlowplugGlowplug Posts: 2,231Expert Adviser
    No experience with speedbox.  All of my Stepdown speedometers are sketchy at best!  I use my iPhone speedometer app when cruising on my own.   The GPS enabled app is spot on as far as speed is concerned!  The cost of that SpeedBox thing would be bucks for other necessary Hudson things for me.   Good luck finding a solution.    
  • bob wardbob ward Posts: 1,301Senior Contributor
    QUOTE "I believe there may be a problem with the gear inside the transmission that drives the pinion gear."

    To check if this the case disconnect the cable from the back of the speedo, have a passenger hold the loose end, go for a drive and check that the inner cable rotates. If its not rotating its not unknown for the inner cable to break.
  • Jon BJon B Posts: 7,329Administrator
    edited August 2
    If the inner cable is not broken, there is another possibility:  for whatever reason, the inner cable is not quite long enough, and the square metal fitting (that is staked to the upper end of the inner cable) barely engages the square hole in the shaft of the speedometer.  Maybe, when you first replace the cable, enough of that upper fitting  engaged the hole in the shaft, and the speedo worked for awhile.  But gradually, gravity pulled the cable down within its sheathing, and its top fitting pulled out of the square hole in the speedo shaft.  And your speedo stopped working.

    Have you pulled the inner cable out of the sheathing and examined it?  If kinked, it needs to be replaced.  Also examine that top fitting.  Has the squared fitting been worn into a round shape?  If so, even if it engages the speedo shaft hole, the connection isn't positive.

    You can buy a new inner cable and cut it to the correct length, then stake the top fitting in place.  Lube and re-insert in the sheathing.

    Here's an instruction sheet on installing cut-to-fit cables (it shows Ford but it's similar construction to Hudsons and others).   https://static.speedwaymotors.com/pdf/LokarFordPDF.pdf  Actually, the cable kit will probably have detailed instructions as to how you can cut the inner cable to the exact size to avoid having the same problem again.  The critical thing is to get the upper fitting precisely located, so that it penetrates just enough of the hole in the speedo shaft, that it won't pull out.

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