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Question: How does a Speedometer cable work?

Discussion in 'The Hokey Ass Message Board' started by plan9, Apr 28, 2004.

  1. plan9
    Joined: Jun 3, 2003
    Posts: 4,082

    plan9
    Member

    I was reading a bit of my manual, and couldnt find any info on how this piece operates..

    Anyone care to explain its workings?

    also... found this program on the net. kinda interesting..

    http://www.bgsoflex.com/speedo1.html

    thankee
     
  2. old beet
    Joined: Sep 25, 2002
    Posts: 5,750

    old beet
    Member

    Just a flexible drive shaft............OLDBEET
     
  3. The cable has square ends on it, one plugs into a gear on
    the transmission the other into the back of the spedometer.

    The spedometer interprets RPM to MPH and moves a needle.

    The cable itself is just a shielded cable, like a choke or
    throttle cable, only difference is the inside piece turns.
    TZ
     
  4. Flexicoker
    Joined: Apr 17, 2004
    Posts: 1,416

    Flexicoker
    Member

    do you just need to know how the cable works? or how the speedo itself works? cause at the speedo end of the cable is an aluminun disk that spins with the cable, close to this disk but not touching is a magnet which is attached to the needle, as the aluminum disk spins it creates a magnetic feild which inturn moves the magnet which moves the needle, and there is a light return spring to provide some resistance and bring the needle back to zero. hope that made sense, and hope that's what you were asking.

    -Eric
     
  5. plan9
    Joined: Jun 3, 2003
    Posts: 4,082

    plan9
    Member

    cool thanks for the breakdown...

    now... for the truth..

    i unscrewed the speedo cable out of the housing, and pulled on the dash a bit... it slid out!

    iam an ignoramus... sweet jesus, save me... did i brokted it? or does it just hook in, and screw back on? [​IMG]

    dash is 57 ford.
     
  6. Smokin Joe
    Joined: Mar 19, 2002
    Posts: 3,770

    Smokin Joe
    Member

    Just push the center cable back in and twist it around till you feel it slide into the tranny gear. Sometimes it won't quite line up and you'll need to undo the tranny end of the housing to get the cable in, but usually it'll line up no problem. Then screw the housing back on the guage. The center cable is just like they said, square on both ends. No biggy. [​IMG]

    P.S. Lube the cable with dry graphite, not oil. Oil will attract dust and gum it up eventually.
     
  7. Satinblack
    Joined: Jan 1, 2004
    Posts: 970

    Satinblack
    Member

    Yeah do what he said, this is a joke right??? [​IMG]
     
  8. plan9
    Joined: Jun 3, 2003
    Posts: 4,082

    plan9
    Member

    [ QUOTE ]
    Yeah do what he said, this is a joke right??? [​IMG]

    [/ QUOTE ]

    NO JOKE.. ive never had to reinstall a speedo cable.

    didnt think i broke it, but i might as well make sure so i dont have to beat my head against the wall when the thing isnt working.
     
  9. daign
    Joined: May 21, 2002
    Posts: 520

    daign
    Member
    from socal

    Not to hijack, but how do you adjust these suckers. I'm off about 20mph too fast.

    Gears wear out?

    -Dane
     
  10. plan9
    Joined: Jun 3, 2003
    Posts: 4,082

    plan9
    Member

  11. old beet
    Joined: Sep 25, 2002
    Posts: 5,750

    old beet
    Member

    daign, might try a new gear with more teeth......OLDBEET
     
  12. Smokin Joe
    Joined: Mar 19, 2002
    Posts: 3,770

    Smokin Joe
    Member

    20 MPH too fast at what speed? Actually, they'll be off a percentage of the speed. Mine's 10% off so if it says 30 it's really doing 33, reading 70 is actually 77, etc. In most cases there's a pair of gears in the tranny tail shaft. One on the cable and one in the tail shaft in a turbo 350 for example. Your local tranny shop should have a chart to show what gears work together right. You may have to switch 1 or both gears.
     
  13. daign
    Joined: May 21, 2002
    Posts: 520

    daign
    Member
    from socal

    I'm goin 90mph on the speedo when really doing about 70mph. So at 30mph I should really be doing 24. That seems about right. I'll have to go play with one of them speedtrap lightup signs that show my speed and swing by the shop. Not sure if its that bad of a thing though. [​IMG]

    Thanks Joe.
     
  14. Mutt
    Joined: Feb 6, 2003
    Posts: 3,219

    Mutt
    Member

    When you go to the speedo shop they'll put your car on rollers connected to a calibrated speedometer. Then they'll tell you to bring it to 60mph or so on your speedo. If the difference between your speedometer and theirs can be corrected with transmission gears they'll install them. If not, they make up an adapter that goes between the cable and transmission to bring it in spec. Make sure that you have the tires you plan on running on the car, because different size tires will change the calibration.

    Mutt
     
  15. thirtytwo
    Joined: Dec 19, 2003
    Posts: 2,636

    thirtytwo
    Member

    daign-c9
    dont you guys write for car magazines???

    this is like high school auto shop 101 [​IMG]

     
  16. plan9
    Joined: Jun 3, 2003
    Posts: 4,082

    plan9
    Member

    [ QUOTE ]
    daign-c9
    dont you guys write for car magazines???

    this is like high school auto shop 101 [​IMG]



    [/ QUOTE ]

    hey DUMBASS... i didnt go to high school... so your point IS MOOT..

    YOUR PROFILE READS:
    " 32 pieces all over, not one car worth a shit "

    I think YOU need autoshop 101... hahaha






     

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