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Re-wire dash

Discussion in 'The Garage' started by bear76, Feb 15, 2007.

  1. bear76

    bear76 1/2 ton status

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    I have decided to re-wire my dash, the whole truck really. I will be ordering the 18 circuit painless kit soon to do this.

    My question revolves around the gauges. I am thinking about going to all elec. gauges rather than a mix of elec. and mech. This way I can keep everthing (wires) bundled together and neat looking. Right now I have a mech speedo how could I change over to a elec speedo? Is there a module of some-sort that would plug into the transfercase where the gear is and just run a wire up to the dash? Is this what the vss does on the newer trucks?

    Thanks.
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Just get an inline 4000 pulse per mile signal generator, and hook its output straight to the speedometer :)

    Factory they use a 40 tooth reluctor ring (40 pulses per driveshaft revolution) which is fed to a DRAC (Digital Ratio something Converter or something similar) that converts the signal to a 2000 pulse per mile, 4000 pulse per mile and a 40.something pulse per mile signal for the ABS if so equipped.
     
  3. bear76

    bear76 1/2 ton status

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    Where would I find such a thing? Also, is it adjustable to differnt gear ratios or is that the function of the speedometer?
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    jagsthatrun.com has a 4000 pulse per mile inline VSS that bolts onto your transfercase where the stock speedo cable is right now. It has an output for a speedo cable, but you could probally just cover that with a pop bottle lid or something similar to keep the output from getting dirty.

    You can find the VSS / DRAC stuff from any truck from TBI truck from 90 up to 95 / 96 before the Vortec 350 appeared. You'll find the electronic speedos in the 90 - 91 K5s, burbs and crewcabs.

    As far as adjusting the gear ratios go, if you go wiht the inline VSS, you'd just change your speedo gears like normal, with the toner ring VSS, you have to install some DIP switches on the DRAC, then flip the switches around to get it to output the correct signals. There is a ton of info on how to modify the DRAC, and what position to put the switches into at www.fullsizechevy.com
     
  5. bear76

    bear76 1/2 ton status

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    Would this be the same if I were going to use an aftermarket speedo?
     
  6. sandawgk5

    sandawgk5 3/4 ton status

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    Yes, If you have a computer it also wants a VSS signal so you would have to find the pin and splice that line to get its vss signal from the VSS rather than the one that is internal to the speedo.

    My truck is mechanical speedo but inside the speedometer is a mirror and light. The mirror spins with the input cable and reflects the light. The number of light pulses is input into a digital to analog converter and fed to the computer so it has a speed input to for calcs for tps/tcc and other things.

    I too am interested as I am looking at putting a stak behind a 465 and might put a 90-91 speedo in place of my mechanical.

    Ira
     
  7. bear76

    bear76 1/2 ton status

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    Mine currently is a mech. speedo. But I'm going to re-wire everything and figured I'd keep it all elec.
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    And yes, you'd need to do the same thing if you were to switch over to a aftermarket electric gauge like an autometer or something :)
     
  9. bear76

    bear76 1/2 ton status

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    Maybe I'm having a hard time understaning things today.

    The vss from the jag place will slide/bolt right in. I run a wire from there (TC) to my speedo. At that point do I just find an aftermarket elec. speedo and hook-up the wire? Or do I need a brain (darc?) to calibrate it? BTW, I don't know what a darc is.
     
  10. mulletman671

    mulletman671 Registered Member

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    If you get an autometer speedo and their sender all you need to run is power and ground to the sender and a signal wire from the sender to the speedo. Then you just program the speedo to your gear ratio/tire size by driving two miles.... quick and easy
     
  11. bear76

    bear76 1/2 ton status

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    Mulletman RULES.
     
  12. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Yep, if you go with the jags that run route, you will not need a DRAC, just hook the speed sensor wire on the speedometer straight to the output from the VSS. Work for either stock, or aftermarket speedometers, assuming they use a 4000 pulse per mile signal. And yes, as the mulletman mentioned, some aftermarket speedometers come with their own sending units to bolt onto the transfer cases's speedo cable outputs :)

    The only time you'd need a DRAC is if you put a toner ring into your transfer case, and need to convert the 40 pulse per driveshaft revolution signal over to something your speedometer can use.
     
  13. NEK5

    NEK5 3/4 ton status Premium Member

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    Since this thread was on topic of using aftermarket elec. speedos, I`m going to bring it back TTT.

    I`m using an 89 harness, but instead of the VSS buffer found on an 89 cluster, I`m using the DRAC that is in my 90 cluster, because I`m usign the NP241 w/ elec. speedo, also from my 90. Are there any aftermarket speedometer (electric) that will work with just the speedo wire coming off the DRAC, and not an aftermarket sender?

    Basically I`m asking, if I can replace the stock speedo, with an aftermarket by connecting the wire that went to the stock speedo, to the aftermarket one.

    TIA!
     
  14. Izzy

    Izzy 1/2 ton status

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    Sweet

    ;)Subscribed... I am in the process of rebuilding my truck and have ordered nothing but Electric autometer gauges.. The post about the Elctro speedo with the thing that hooks up is gonna help since I got the sending unit also... Thanks for the post.... :D
     

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