basic questions about VSS

Discussion in '40- & 55-Series Tech' started by workingdog, Mar 11, 2017.

  1. workingdog

    workingdog

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    I need a VSS on my 2001-ish 6.0 Vortec in front of a NV4500. I was looking online and I've hard about two options which I am looking for more detail on.

    Some have talked about putting a device on the speedo output that will generate the appropriate signal for the ECM, but I can't find what they are talking about. But if I could find such a device, I assume it goes on the back of my xfer case where pictured IMG_2585.JPG IMG_2584.JPG .

    Some have talk about Jags that Run device that goes onto the unused output of the transfer case - also pictured. But it seems like a lot of work to get a VSS signal and I don't think I have enough room between the frame cross member and the xfer case to fit it.
     
  2. Rusty 72

    Rusty 72

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    You can install a VSS on your transfer case. Look like there is enough room. Another option is having a cable made and install the VSS under dash then another short cable from VSS to speedo.

    Dakota Digital make some very nice interface modules might try them also.
     
  3. sadam_husain

    sadam_husain

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    This is probably the vss that you're referring to that fits onto the back of the transfer, it does look like you don't have much clearance from the tube crossmember, I aren't running a vss on my 6.0 vortec it runs and idles fine and has never come close to thinking about stalling but would probably give me better fuel trim tables if I was running one

    Toyota V8 Conversion Parts for FJ40, VSS Reluctor Ring Kit Stealth Conversions
     
  4. workingdog

    workingdog

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    Yes, that's it. It looks too deep for the space I have. Plus, the speedo port would seem easier all around.

    I'm getting near stall coming to a stop. Otherwise it idles fine. I've been told it's the lack of a VSS. Idle is set at about 840 right now. This supposedly has a 'stage 2' cam in it, I don't know if that is aggravating the idle problem.
     
  5. workingdog

    workingdog

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    So, been reading some more, ordered a VSS from Dakota Digital - and now I'm not sure I need it. Someone on Mud says that you have to have the VSS to get the idle right when coming to stop, but the reading I did today indicated that the only thing the VSS is good for is Cruise and the auto tranny. Others says a VSS helps a lot with timing. Trying to figure out truth here.

    Is my dying when stopping due to no VSS or should I be looking at the idle control motor?
     
  6. SMG

    SMG SILVER Star

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    Interested in this as well, Hopefully someone that knows more about this will chime in.....
     
  7. Rusty 72

    Rusty 72

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    My experience, years ago I did a 3.1 mpfi swap from a Camaro into a S-10 2.8 TBI. Used a wiring harness and custom chip from Turbo City. They programed the VSS out. Had idle issues from day one. Sometimes it would not idle below 2500rpm other times it would die from so slow idle speed. They burnt several chips never got it fixed until a VSS was added.

    2nd no VSS swap, 1987 350 TBI into a 1947 Chevy car. Had chip burnt without VSS. Idle was real slow to point it would die if stopped for 30-45 seconds. The reason it died was it idled so rich it flooded it out. New stock chip and VSS was added. Ran fine after that. Turbo City burnt both chips and kept saying VSS is not needed. Every swap I did after that I kept the VSS. No problems with any of them.
     
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  8. workingdog

    workingdog

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    That is interesting. Thank you for sharing your experience. I've heard people with experience similar to yours. Then you hear people like Howell saying a VSS is not necessary. I've heard it's used for timing and defueling. Certainly, as the engines get newer, the odds of it being used grow. I'd love to find someone that actually knows. My VSS should show up in a few days and, if I can find the wires in the harness, I'll what it does.
     
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  9. sadam_husain

    sadam_husain

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    the need for a vss may be specific to what FI you are using, neither my lt1 or my lq4 have vss sensors and both of them have never has any sort of idle, hunting or stalling issues, the only thing I get is minor backfiring when decelerating down steep hills as it wont get a fuel shutoff decel signal
     
  10. Downey

    Downey

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    When Downey was trying to get the TBI conversion smog legal (never did) the engineers at the Federal Testing Lab gave me a list of all the things a VSS does, cripes, I wish I would have saved that list for this forum. As I recall the VSS works with the 02 Sensor to perform about 7 or 8 different functions. Included in the "idle functions" (everything below 2 mph) is fuel enrichment on starting, automatic choke functions, and 1st gear-low range idle functions when wheeling. Some of the others are auto tranny shifting, cruise control, burn-off of fuel upon deceleration, etc.. I honestly don't know how these issues are addressed in a reprogrammed ECU chip?????. My opinion is those who claim their vehicle operates properly without a VSS just don't know how smooth/drivability their rig should be ????
     
  11. workingdog

    workingdog

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    Thanks Downey - I believe all that - and I think the year makes a lot of difference, as cars got older I'm sure the VSS got more important. WFO got off the phone with Howell and they are emphatic that without an A/T, the VSS does nothing. There are no wires in any of their harnesses for VSS on cars with A/T.
     
  12. Downey

    Downey

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    We worked with Howell when developing the Landcruiser TBI conversion. We never achieved any drivability until we aborted all of the Howell programming and went to 100% stock Chevy S-10 programming with 100% of the sensors GM designed into the system.
     
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  13. pjohnson

    pjohnson SILVER Star

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    Which vss did you get? I am assuming the speedo cable output version. Will it fit the tcase speedo location?
     
  14. terrx

    terrx

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    Howell harnesses for pre-vortec and early vortec EFI using TBI & TPI included VSS and the ECM used it, as Downey mentioned. Just FYI.
     
  15. workingdog

    workingdog

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    So, I finally installed HP Tuner and have used it to solve a bucking, hesitation problem, but in working on my idle if found out the ECM relies on vehicle speed to determine Throttle Crack. So there at lease 2 tables with a manual transmission that use speed. And your throttle won't crack without them, meaning you'll die coming to stop lights.
     
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