VSS for ECM and Spedometer

Discussion in 'Technical' started by leeinphx, Nov 23, 2022.

  1. leeinphx

    leeinphx Member

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    I parted out a 92 t-bird for the 5.0 engine. I used the VSS signal generator from that vehicle that goes in where the spedo gear is on my C-4. It is wired to the ECM (using an aftermarket engine wire kit). I just ordered a gauge package (New Vintage ~ Performance Series 2) that also uses the VSS signal. Does any one know if I can wire these in parallel at the VSS sensor to feed both, or am I going to have to find a way to get the speed signal out of the ECM or install a second VSS signal generator somehow?

    Thanks for any input or suggestions - Lee
     
  2. bmcdaniel

    bmcdaniel Senile Member

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    I'm betting it would drive both, the ECM and gauge probably both have high impedance inputs. How many wires come out of the signal generator?
     
  3. leeinphx

    leeinphx Member

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    There are two wires coming out of the VSS at the Tranny.

    Worst case, I just wire them in and can change it up if it doesn't work out. In reading another ford forum more related to the donor vintage, they believe the ECM mainly uses the VSS signal to manage idle as you come to a stop, so that is not a critical input to the ECM. Some report running without that input with no negative affect and at least one has just spliced it in, so it looks like I'll not have to worry about it for now, I can make it work out.

    It will be interesting to see what New Vintage says in their instructions, not much online as far as resources from them. I will be doing the dash conversion to the dual gauges and will try to capture the wiring issues in a write up if there is anything quirky.
     
    Last edited: Nov 25, 2022
  4. bmcdaniel

    bmcdaniel Senile Member

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    Two wires, it's probably just a magnet spinning past a coil of wire. I still think it will work. Some people splice into them to attach cruise controls without issues.
     
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  5. Krazy Comet

    Krazy Comet Tom

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    AODE, 4R70W & other electronic trans will not shift without speed sensor input. My Aerostar quit shifting, that was problem. Still ran fine.

    I seem to remember early speed densety systems only used it for speedo & cruise control(separate module) operation. By late '80s Lincoln's cruise had been integrated into ECM.

    Straying, after reconnected the cruise control on my '88 T-Bird with 4cyl to 5.0 conversion, it'd engage with a real vengeance. Researching, I found modules for half motors and 5.0 were different. Pulled one from '86 LSC that donated engine and found there was adjustment inside that affected veracity of acceleration. Modules were same but calibrated for specific HP/weight vehicles.

    Here's sensor output on scope spun with drill. Dunno why it's rotated 90* but you get idea.

    speedsensoroutput_zps71ivhur7.jpg
     
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  6. leeinphx

    leeinphx Member

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    Thanks to both of you for the feedback.

    I have a C4 in it now and may put in an AOD, saving my AODE for another project. So no worries there. The key concern I really had is that the pulse is not degraded by receiving at more than one source, but have not seen that as an issue with the research that I've been able to find on the internets (for what its worth) and what you have both mentioned in your replies.

    Cruise (saved from the donated '92 cougar) may go back on this engine someday, so will deal with that at the time, for now, looks like I'm good to go. Certainly don't want to get into any deeper issues by going with potentially incompatible parts, hence saving everything I could off the donor.
     
  7. 71Mavrk

    71Mavrk Member

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    The Dunn Rite harness I purchased did not have any wiring for the VSS. When I got with my tuner, there were some areas he could not tune as well without the VSS input. Off hand, I cannot recall what they were, but I think they were idle related. I added the circuit in.

    Micah
     
  8. Mavaholic

    Mavaholic Growing older but not up!

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    I know my Speedhut speedometer gauge uses a VSS signal and also has a VSS output wire for cruise control. So it should work.
     

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