Speedometer Reading to Slow

Electrical and Ignition

  1. 69RRBeepBeep

    69RRBeepBeep Member

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    We just installed a refurbished original factory instrument cluster and now that new speedometer is reading 10 MPH slow. When you first start you must get to 20 to read 10 and it continues to read 10 MPH off throughout the speed band. Has anyone seen this before?

    UPDATE - We validated the gearing is correct today, for a 3.91 with an overall tire size of 26 we needed a 2538940(Orange), which is what we have. We are still having the problem and checked to see if there was any bind in the cable, nothing seems hard when we checked it. Lastly it is coupled to a 4 speed manual.
     
    Last edited: Jan 19, 2019
  2. Russ69Runner

    Russ69Runner Well-Known Member

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    Is it an automatic trans. or manual. Manual call summit and they have the rite gear for it. Or brewers if you know the gearing in the rear end and tire height. Hope this will help. Russ. :thumbsup2:
     
  3. dmartin

    dmartin Well-Known Member

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    Drive faster! Check to see if you have it in the right notch as far as the tranny gear drive and make sure you have the right color
     
  4. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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  5. 69RRBeepBeep

    69RRBeepBeep Member

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    Thanks for all of this. Something I left off, we have not changed out the rear end (3.91) nor the tires at this point and it is a 4 speed manual. The only thing new is the instrument cluster, we pulled out the old one, place in it a new refurbished cluster, hooked everything up and check to ensure the speedometer cable wasn't bound in any way and took it out for a test drive. When we did that is when we noticed a 10 mile an hour difference. Today we took off the cable and found it to have a 2538940(Orange) gear, which is exactly correct based upon the specs provided by 69hemibeep (thanks BTW). Not sure what dmartin is saying about the tranny gear, can you explain? Thanks for all the help so far.
     
  6. Basketcase

    Basketcase Keeper of the Green

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    the gear for the speedometer that goes inside the transmission, that the end of the speedo cable goes to. In Ohio we don't worry about correct speedometers. The Governor has these really polite men to let us know how fast we drive.....

    34416255090_8afba178a2_b.jpg
     
  7. droptop

    droptop Well-Known Member

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    Sounds like the "refurbished" gauge cluster is the issue.
     
  8. Russ69Runner

    Russ69Runner Well-Known Member

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    Yep use to keep the green stamps in the glove box from these guy's. They just loved loud pipe's. :lol:
     
  9. Russ69Runner

    Russ69Runner Well-Known Member

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    So Call Brewer's. They would have the rite gear for the transmission. Who did you get the Speedo from. They may have to make a change for you. Also what did this speedo come out of. Was it a runner or something else.
     
  10. quikbird

    quikbird Well-Known Member

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    Remember the speedo works by having a magnet attached that actually spins the needle could be a problem anywhere in that system
     
  11. Russ69Runner

    Russ69Runner Well-Known Member

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    Yes had an MPH meter on a tractor and all that had fallen apart the worm gear drive was gone. Of course it was made of plastic. May have to send it to a shop to calibrate it or check the mechanism in side. Still think the gear at the transmission is wrong.
     
    dmartin likes this.
  12. dmartin

    dmartin Well-Known Member

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    Yeah
    the orange gear you were mentioning is what I’m talking about
     
  13. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    I had my Valiant speedometer repaired at Redline in California, did the measurments and put the 33 tooth gear in and it was 5 off all the way up in speed which I thought odd. So I went to a 32 tooth which is supposed to be about 3mph difference, no change. Got me scratching my head so I'm going to call them today.
     
  14. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    Ok mine is 5mph off at any speed so they said look at the needle when stopped it should be on zero not above or below if so it needs adjusted. If all that is good and the speedo is 10mph off regardless of actual speed there is a metal plate on the back that can be moved up or down to adjust it. I believe he said up makes it faster. If it gets worse with speed its the gear in the transmission.
     
  15. Dibbons

    Dibbons Member

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    When I purchased my '72 Satellite Sebring Plus, the orginal 318 and Torqueflite had been removed from the vehicle. I changed the gaskets in the motor and replaced it in the vehicle, had the automatic transmission rebuilt by a local shop and replaced it in the car. Never touched the original 8 1/4 rear end with 2.76 tag on the cover plate. Of course, when purchased, I could not drive the vehicle with the drive-train on the garage floor of the previous owner so I did not have a clue about the condition of the speedo or other gauges at that time.

    I had Redline restore the gauges, mainly to convert the ammeter to a volt meter. Now with everything back together, the speedo is reading way too high.

    There is absolutely no reason to believe that the installed vehicle speedo pinion gear would not match all of the drive-train which is still in "as manufactured" original configuration. Tires are 215/70-R14 which is about right for factory tire height.

    I am very interested on any follow-up that 69hemibeep has to offer. I really would like the speedometer to display an accurate reading, if you know what I mean. Thank you.
     
    Last edited: Feb 1, 2019
  16. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    My plate is full right now so it will be awhile before I get to it. I do have an extra cluster I can look at today and see if it makes sence
     
  17. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    I took the extra cluster apart and I don't see any metal part that would slide for adjustment!
     
  18. Dibbons

    Dibbons Member

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    I have an extra cluster for 71-74 BBody Rallye dash and an extra speedometer for that. Looking at the extra speedometer (which is loose in the box right now) I don't see any way to adjust the speedometer one way or another.

    The needle has a small, weak return spring and there is the aluminum drum and a pair of arms that spin around the drum. No slots or any kind of way to calibrate the speedo that I could find. The mystery continues. The answer must lie in the inner sanctum of some Guru up on the mountain tops.
     

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