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Thread: Speedometer replacement

  1. #1
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    Speedometer replacement

    I have a Ferrari F40 with Fiero GT instrumentation. My speedometer is in Kilometers(Canadian import) and I would like to replace it with a real F40 speedometer. Other than the physical installation, what would be the procedure to hook it up to existing wires and the transmission? Thanks

  2. #2
    Senior Member Don's Avatar
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    The Fiero gauge cluster has a speedo buffer that takes the VSS signal from the transmission sender, buffers it to 4000 ppm and 2000 ppm and pushes it out to the other parts./

    The 2000 ppm line goes to the cruise control and the 4000 ppm wire goes to the speedo and the ECM. THESE HAVE to remain in the mix to have the Fiero run properly.

    I am going through the same thing right now.

    86-88 GT gauge clusters have the speedo buffer board you want but any other years or models will not have what you need. If your cluster is 86-88 GT then you are golden. Leave the speedo connector in place (don't cut any of the wires from the frame side of the connector) and take the cluster apart. Behind the speedo side of the cluster where the speedo connector connects to the cluster is the board you want.

    All you need to do is keep the board in the wiring inside the dash and take a wire from the 4000 ppm output (yellow wire on the connector) and put that to your after market speedo. Your after market speedo will need to be calibrated but that will part of the instructions.

    If you don't have that board..... You can get a buffer from an 85-89 Firebird from a wrecker (small yellow plastic box about the size of a pack of matches in the dash near the steering column) or go find another 86-88 GT Fiero cluster. No other way around it unless you buy an after market buffer package from Dakota Digital or other one.

    Once you get the gauge cluster apart, post a pic of the speedo buffer board and I will be able to tell you if you have the right one or not.

    Cheers
    Don
    308 Ferrari replica
    Prova Countach 5000QV

  3. #3
    Senior Member Don's Avatar
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    I have since updated my own build and should post here as well to get the info out for Fiero base owners.

    If you want to use the original ECM, you can use a later model VSS buffer and wore it into the Speedometer connector behind the dash.

    The link below explains the wiring needed and the vss buffer comes from GMs between 88- early 90's? Make sure the VSS buffer box looks like the one pictures below.

    Go to the bottom of the linked page for the wiring. Don't go with the actual placement of the wires in the images but go by the colours,. They may be in different positions depending on your year and vehicle configuration. Colour of the box may be different as well but the shape seems to stay constant.

    Electrical pg. B

    Also copied the images below in case that page goes away.

    Enjoy
    Don

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    Last edited by Don; 09-22-2014 at 05:09 PM.
    308 Ferrari replica
    Prova Countach 5000QV

  4. #4
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    Quote Originally Posted by luvatenor View Post
    [SIZE=4]

    ... I would like to replace it with a real F40 speedometer.
    Other than trying to find and pay for a speedo for a $2 million car, you're gonna need to find out what kind of signal it takes, i. e., how many pulse per mile (ppm) it needs to work.

  5. #5
    Senior Member MacGyver's Avatar
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    Quote Originally Posted by Don View Post
    I have since updated my own build and should post here as well to get the info out for Fiero base owners.

    If you want to use the original ECM, you can use a later model VSS buffer and wore it into the Speedometer connector behind the dash.

    The link below explains the wiring needed and the vss buffer comes from GMs between 88- early 90's? Make sure the VSS buffer box looks like the one pictures below.

    Go to the bottom of the linked page for the wiring. Don't go with the actual placement of the wires in the images but go by the colours,. They may be in different positions depending on your year and vehicle configuration. Colour of the box may be different as well but the shape seems to stay constant.

    Electrical pg. B

    Also copied the images below in case that page goes away.

    Enjoy
    Don

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    Don,

    I wish I had known you knew all this a year ago when I was working on my cluster. I know, I know, I didn't ask........... wright!

  6. #6
    Senior Member Don's Avatar
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    Didn't know all this a year ago either Sean.....

    It has been an interesting few weeks with this wiring crap..... I have learned more than I ever thought I would have to....��

    It is good info to have for the future though.

    Cheers
    Don
    308 Ferrari replica
    Prova Countach 5000QV

  7. #7
    Senior Member lurate's Avatar
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    Don,
    I read your post quite some time after I had begun the wiring process for Amida's 355 interior. Thus, your instruction to leave the wiring to the pod intact.....well. What I know I have is a yellow speedo wire and the old 88GT board from the speedometer. Would it be simpler for me to get the Universal Speedometer Signal Interface
    From Dakota Digital you reference or is there some easy wiring from here?
    Attached Images Attached Images  

  8. #8
    Senior Member Don's Avatar
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    Lurate

    you should b able to take the buffer card off the rest of the cluster. you only need the piece you are showing on top.

    you then just use the Speedo plug off the Fiero wiring harness and pull the Speedo wire off the wire the currently goes to the Fiero Speedo. mount the board somewhere safe up on the steering column area. Like Corson said in the thread, you have to find out what pulses the Speedo accepts. if it is 2000 or 4000, you are golden. if it needs something else then you will need to look at a digital Dakota etc. that has more outputs.

    keep us updated on how it goes for you.

    cheers
    Don
    308 Ferrari replica
    Prova Countach 5000QV

  9. #9
    Senior Member lurate's Avatar
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    unfortunately I'm afraid the speedo plug is long gone....

  10. #10
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    Luvatenor,
    If you can live with a much cheaper but undetectable VDO speedo with a paper Ferrari face, that speedo is fed by it's own GPS a there are no sender wires.

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