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Thread: Speedometer problem

  1. #1
    Join Date
    Aug 2015
    Location
    Portlandia, Oregon USA
    Posts
    202

    Default Speedometer problem

    My factory SW 503-C speedometer has sat still for over 3 years and now that the ambulance is driving again, it reads about 15-20 MPH lower than the speed I'm traveling. The cable is new NOS that I pulled the center out and cleaned with solvent to remove all the gummy lube and then I re-lubed with speedometer cable lube before I installed it. The speed seems to be more off the faster I go.
    I'm basing this assessment on both GPS and generally knowing the speed of the traffic around me on roads I'm familiar with.

    I can't find anything on here about being able to service or open up that speedometer. Anyone have any recommendations in this area or had this same problem?

    I also just posted a "wanted ad" for a good used speedometer in the classified section of the zone. Please let me know if you can help me out either way.

    Cheers,
    Bryce
    1969 M725 ambulance

  2. #2

    Default

    Quote Originally Posted by brycer1968 View Post
    My factory SW 503-C speedometer has sat still for over 3 years and now that the ambulance is driving again, it reads about 15-20 MPH lower than the speed I'm traveling. The cable is new NOS that I pulled the center out and cleaned with solvent to remove all the gummy lube and then I re-lubed with speedometer cable lube before I installed it. The speed seems to be more off the faster I go.
    I'm basing this assessment on both GPS and generally knowing the speed of the traffic around me on roads I'm familiar with.

    I can't find anything on here about being able to service or open up that speedometer. Anyone have any recommendations in this area or had this same problem?

    I also just posted a "wanted ad" for a good used speedometer in the classified section of the zone. Please let me know if you can help me out either way.

    Cheers,
    Bryce
    That's exactly how mine works: farther off the faster I go, and it was made worse by the Superlugs I got, which are taller than NDCC's.

    I remember a place called North Hollywood Speedometer from my Fiat/Abarth days-- maybe they're still in business & can help you out.

  3. #3
    Join Date
    Aug 2015
    Location
    Portlandia, Oregon USA
    Posts
    202

    Default feeling a little sheepish now

    I thought about my speedometer problem a little more and it dawned on my this weekend that the speedometer error I am seeing is consistent with the amount of gearing change I introduced into the drivetrain when I re-geared my axles from 5.87 to 4.56 gears. Mystery solved and sorry to have wasted anyones time.

    Cheers,
    Bryce
    1969 M725 ambulance

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