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VSS sensor

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Cavalry, Feb 26, 2001.

  1. Cavalry

    Cavalry 1/2 ton status

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    I am planning a EFI conversion. I am going to go with a GM setup but probably mid 90's EFI. I will need a VSS for it to work properly, I located one in the junkyard off a 88K5. Can I use the 88 VSS on say a 94 ECM? I know the 88's VSS location is in the speedo head but where exactly? Can I just swap the sensor in or do I have to swap heads. I know there are also trans mounted VSS avail, where do I get one?

    Luke
    84 K5
    [​IMG]
     
  2. MudRebel350

    MudRebel350 1/2 ton status

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    Im pretty sure u have to use the computer and vss from whatever efi setup u r using becasue only that computer knows how much fuel to meter and so on. I dont think it can be from the 88 K5. But if someone proves me wrong then, I'd be very surprised.

    JD
    former owner of an 88 Jimmy and 2 87 K5's
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    VSS is an input for speedometer cable revolutions per mile. It reads a little tag on the speedometer cable via light reflection. Thats 1000RPM per mile. GM used the 1000rpm/mile measurement from 1981-1987 at least, no reason to change later on. The VSS, in conjunction with the ECM, controls lockup of the torque converter, but its not the only input for lockup. The VSS also handles cruise control, but that is seperate of the ECM on our (1981-91 K5's) trucks. I can't imagine the VSS is a problem, since many people running mid 80's cars, which use the SAME VSS as our trucks, do the EFI swap with no complaints about the VSS. Sorry I can't say yes or no, but my unqualifed answer is you can probably use the olderVSS with the newer system.
    BTW, the VSS lead bolts to the back of the speedo head. Easy to see, 1/4" or smaller screw holds it on.
    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  4. realsquash

    realsquash 1/2 ton status

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    I can't recall what speed your VSS is, but mine turned out to be 4000 ppm. If it's a 94, it's prolly a 4000ppm, but I can't be sure. What ECM and what are the numbers on the "chip" of the 94's ECM??? I can tell you exactly for sure what u need.

    Squash
    <A target="_blank" HREF=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</A>
     
  5. Cavalry

    Cavalry 1/2 ton status

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    I already have a sensor in my rig for the cruise (little hall effect deal) where does the EFI VSS go? Later model VSS uses electronic speedo's not cable so how would I hook it up?

    Luke
    84 K5
    [​IMG]
     
  6. K5 NUTT

    K5 NUTT 1/2 ton status

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    All pre 87 K5's without TBI have no vss. I am doin the TBI swap currently. Just ordered my harness from Howell....and a 2 pulse speed generator for vehicle speed input to the ecm...it runs $85. You install it at the transfer case..and then your speedo cable connects to it. I'm going to run the a stock 88K5 ecm i have in the garage..its a 7747 ecm....mid 90's ran a different ecm i believe which changes things a bit as the ecm is faster. I would call Howell and get the low down before attempting to gather parts...so you get what you need the first time. I still have to by the late model Dist...sensors and finish building my TBI unit itself..the new GM 350 injectors cost me $124 a pop at the good guy price..ouch...but worth it when this is all done!

    Azblazer

    1979 K5
    1976 K5 Chalet
    1972 K10 Suburban
     
  7. pcorssmit

    pcorssmit 1/2 ton status

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    Good luck with your TBI swap, however early '80's trucks used the optical VSS for the cruise control. My '83 had one, but I had to swap the box out for one out of a car (got it from a '84 caprice w/ cruise and feedback carb).

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes, cars and trucks carbed, got the VSS to control tranny lockup. My '83 truck had it, and I can guarantee all US 1981-1988 A/G bodies (RWD montes, cutlass, malibu, etc) used the VSS, and they were all carbed, minus the TR and TM.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  9. Cavalry

    Cavalry 1/2 ton status

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    OK so if I snag a VSS out of another GM can I hook it up to my speedo? Or should I snag a 88 K5 cluster with the VSS? Is it inline on the cable or does it work off part of the speedo? I want to retain my cruise control so how does that work in. I would prefer to use all GM parts and no aftermarket. Sorry if I'm being so dense about all this, I dont think I have ever even seen a GM VSS.

    Luke
    84 K5
    [​IMG]
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    As long as your truck is about an '82-whenever, yes, it will work, since the speedo "head" will have the provisions for the VSS. Basically a slot for the VSS light emitting end, and the screw that retains it.

    The VSS bolts to the back of the speedo head. From there, the wires travel to a small box (the "buffer") which in most cases is like a light green or yellow color. From there, it should split, and feed the cruise control box, again probably depending on year, and the ECM.

    One other option I just remembered, was an electric speedo from a later K5, Suburban, etc. I wouldn't think they woul dhave botherd to go electric, but my dad, who knows what he is doing, or so he likes to think, SWEARS that just the other day he was going to pull a speedo because it had trip odometer, and he discovered it was electric driven, not cable. If he was going to pull the speedo, it must not have been much different looking than what ours look like, and he is pretty sure it was a '91. if anyone has a service manual for that year Blazer, Suburban,etc, proof of that may be in there. GM may even still sell the speedo's from the 91's. if the part number is different from say a 1985K5, then that might confirm the electric speedo drive..either that or someone here might know conclusively!

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  11. K5 NUTT

    K5 NUTT 1/2 ton status

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    If you read the book on TPI/TBI swaps by www.jagsthatrun.com....they show and aftermarket vss installed at the cruise control box...this is not a good place to put an aftermarket vss as the cables bounce around quite a bit on the older rigs..so it will have to be mounted inline with the existing cable coming out of the xfer case. The signal generated for the cruise box is not sufficient enough for the ecm...and since pre 87 K5's never had a vss you will have to run the Howell unit to make the tbi function correctly. The nice thing about the Howell harness is that you can run a stock 87 to 90 K5 ecm and utilize the factory cal pak and prom...no extra cost for custom chip. I don't have the late model R/V manual for the info on the cluster...i guess its time to call and order one from Helm. (K5-Suburbans-crew cabs 88-91- hold overs from new body style are the R/V series..not the C/K)

    Azblazer

    1979 K5
    1976 K5 Chalet
    1972 K10 Suburban
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Why are you saying pre '87 never had VSS? They did, and it was every year they had a 700-R4 installed.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  13. mattman

    mattman 1/2 ton status

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    I believe starting with 1990 R/V, the speedometer went electric driven by the VSS, no longer by the cable. My '90 Jimmy only has the VSS cable coming from either the tranny or t-case for speed.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    It would definitely make sense on an electric speedo truck to intetgrate the VSS, so that would be a nice setup probably!!

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     

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