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Late model VSS on an Early model TBI?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fortcollinsram, Feb 18, 2003.

  1. fortcollinsram

    fortcollinsram 1/2 ton status

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    Okay, I am sick of my SES light screaming at me all the time...and I am doing away with the stock gauges in favor of an AutoMeter setup...I would like to get an electric speedo from Auto meter. Well, can I install a late model "toner ring" in my 205 and use a late model VSS to run my electric speedo from AutoMeter AND to send a signal to my ECM? Will the signal my ECM gets form the VSS on the 205 be the same as the signal it currently gets from the buffer behind the mech. speedo? I just need a way to get a VSS signal and a signal for a aftermarket speedo off the t-case...any ideas? Thanks...

    Chris
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, the NP241 toner ring setup will work, (at least out of the 90-91 K5's,etc) but at some point they changed the "pulse" of the VSS. You need a 2 pulse setup, which the 241 stuff from '90-91 is.
     
  3. u2slow

    u2slow 1/2 ton status

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    What are the different pulse versions? I know for a fact a '91 NP241 (stock sensor) will work with a '98 Vortec ECM
     
  4. fortcollinsram

    fortcollinsram 1/2 ton status

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    So you think I can use the 241 toner ring to send a signal to the VSS which, in turn, will run BOTH my speedo and send a signal to the ECM? Didn't Steve Fox have a similar setup when he installed is doubler?Does the toner ring just slide onto the the tailshaft of the 205 and replace the mech. speedo drving gear? What about stealing a toner ring/VSS from a later model Dodge? Is that the same pulse style as I need? Thanks for the help gang...

    Chris
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Check out http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html

    They have a few options there, but dunno what would work for you since you want to run both. I would certainly think the speedo maker could recommend something.

    Do a search for the 241/205 toner ring setup, it's not *that* expensive.

    I tried that dodge idea, but NO ONE seems to know anything about it, and I'm not going to buy a dodge shop manual just to find that info out. Personally I like that idea the best.

    Just because it's on the internet doesn't mean it's true, but the jags that run site doesn't agree with the statement that later VSS will work with your 2 pulse setup. However, I don't own a 1998 C/K truck so I can confirm nor deny it myself, nor have *I* tried it myself. With GM doing away with 2 pulse in the early 90's, even on a truck I don't see them sticking with 2 pulse that long.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html is all I have to work with. It doesn't agree with your statement, but thats also a web page and not necesarily fact as I know it.

    Curious, since that was a swap (right? 241 with Vortec?) how was it setup? No trouble codes/wiring harness hacking at all, and the ECM has been "scanned" to see if VSS input is equal to actual road speed?
     
  7. HarryH3

    HarryH3 1 ton status Author

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    As long as the VSS input sees a signal of some type, it probably won't set the check engine light. However, this doesn't mean that the computer is getting valid data, just that is getting some data. /forums/images/graemlins/shocked.gif So this would make it seem like it's working properly... /forums/images/graemlins/wink.gif
     
  8. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    You can install the 241 toner ring in the 205 but it will have to be machined down just a tad and a new access point made in the tailshaft so the VSS sensor can thread into that and read the tonner ring. Donovan can do all that for you, his number is 303-423-6152, he is in Wheat Ridge. /forums/images/graemlins/thumb.gif
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Thats my assumption, but short of checking ECM vehicle speed and comparing it to a chase vehicle speed, I don't see how anyone would ever know.

    Unless the ECM said you were doing 80 when you were doing 10, or vice versa, which would be obvious. (which I'd kind of imagine would happen if you more than double the pulses)

    Economy could also be an indicator, either what you "believe" you are getting ends up as really high or really low, outside the ranges of probability.

    I'm just skeptical because the two pulse VSS came out so early (I think '80 for CA cars) and was gone by the early 90's in cars. I don't see GM carrying it on in the trucks much longer than that, especially as competitive as the light truck market is, along with how huge the power difference was on the Vortec truck compared to the previous TBI ones. (meaning leaps in technology, not just a step)
     
  10. fortcollinsram

    fortcollinsram 1/2 ton status

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    Thanks Steve...I will give him a ring....I will probably hold off on it until I get Spickler's tranny and t-case...that way I can take to case in for him to machine and work his magic...

    Another thing for all you guru's...I was poking around AllDataDIY.com and noticed that the trucks that have the electric speedo first send the signal through a buffer, or DRAC...How much are these deals from GM? I guess it is a must since, it converts the AC signal to DC so the ECM understands it...Thanks gang

    Chris
     
  11. jmd

    jmd Registered Member

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    "a '91 NP241 (stock sensor) will work with a '98 Vortec ECM "

    That's kinda like saying a Painless TPI harness "works" eh?

    The signal is a difference wave, and the pulses are quite different in number.

    Just because it doesn't set a code doesn't mean it's working properly.

    Matthew
     
  12. u2slow

    u2slow 1/2 ton status

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    Fair enough... /forums/images/graemlins/wink.gif

    It didn't throw a code, drove well, and the speedo registered bang-on. Are the two pulse types much different? Does it make any "real" difference to the ECM?
     
  13. u2slow

    u2slow 1/2 ton status

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    The NP241 in question here was sourced from behind a 4L80E in a '91 Suburban. It got mated to the '98 4L80E. JTR's info might be off a little... after all, they don't account for TBI applications that use no VSS at all.

    This is the truck it all went into. Drove great! Too bad he didn't have any $$$$ left over for suspension /forums/images/graemlins/rolleyes.gif
    87 K30 w/Vortec 454
     
  14. jmd

    jmd Registered Member

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    Wasn't the VSS TBI hearsay at this point in time, due to a possibly incomplete wiring diag? No verified examples had been found?

    [ QUOTE ]
    It didn't throw a code, drove well, and the speedo registered bang-on. Are the two pulse types much different? Does it make any "real" difference to the ECM?

    [/ QUOTE ]

    The two pulse types are uninterchangable, and they're greatly different in #.

    Was the P/N switch grounded perchance? That would cause it to throw no VSS codes, yet "run" but not "run right."

    Matthew
     

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