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Thread: LS Swap w/ Dakota Digital 8k pulse generator

  1. #1
    Tuner in Training BrandonHall10's Avatar
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    4x4 LS Swap w/ Dakota Digital SEN-01-4160 *SOLVED*

    *Solved*

    Here's the story: I have a 1984 K10. I swapped in a 2001 5.3/60e and kept the original '84 NP208 transfer case. I needed a simple way to generate VSS pulses for the PCM and also retain the original cable drive for the mechanical speedo. I chose the Dakota Digital SEN-01-4160 Pass-Through Speed Pulse Adaptor. Problem is, the DD pulse generator produces 8 pulses per speedo cable revolution (or 8000 pulses per mile). The PCM wants 40 pulses per output shaft revolution. Here's the math to solve the discrepancy.

    First, apply the 31? tire size (30.5 actual) and 2.73 axle ratio correction to all the shift tables using the "Gear/Tire Wizard." Leave the 40 pulse per trans rotation setting alone for now.


    Trans revolutions per mile:
    Tire size (30.5" diameter, OR 684 revolutions per mile) multiplied by the axle ratio (2.73), will result in 1867.32 drive shaft revolutions per mile. *Calculated by Gear/Tire Wizard*


    VSS P/Rev - Trans:
    8 pulses per rev (Dakota Digital output) DIVIDED by 1.9444 (35 driven / 18 drive) from the speedo gear output. Equals 4.11438 Pulses per trans revolution *Manually calculated*


    VSS Pulses per mile:
    1867.32 (drive shaft revolutions per mile) DIVIDED by 1.9444 (sensor revolutions per driveshaft revolution). Equals 960.358 sensor revolutions per mile. 960.358 (sensor revolutions per mile) times 8 (Dakota Digital pulses per revolution output) equals 7682.864 Pulses per mile. *Manually calculated*



    That's it. No welding reluctor rings to output shafts. No drilling speed sensors into adapter housings. Just a $50 pulse generator and 15 minutes to instal it. The numbers are specific to my application, but it's easy enough to plug in different values for another set up. Big thank you to Brendan at LT1Swap.com for walking me through this.

    Last edited by BrandonHall10; 06-30-2021 at 10:57 PM. Reason: Posted solution

  2. #2
    The Dakota Digital Help Desk could answer this question in a nanosecond and explain the mathematics. They were very helpful with my DD HDX set of gauges.

    Rick
    1970 Chevrolet El Camino LM7 5.3 liter mill and a 4L60E transmission.

  3. #3
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    When an LS conversion involves a vehicle that uses a cable driven speedometer, generating a useable VSS signal is optimal. There are two readily available means of generating a useable VSS signal to the PCM (computer) - a cable driven VSS generator or a GPS unit that outputs a pulsed VSS signal (Dakota Digital offers both of these options).

    The most common cable driven VSS pulse generators output 8000 pulses per mile (8K PPM), or 16K PPM. These lower PPM rate generators will sometimes cause issues with torque converter going into a fully locked state - excessive slip can sometimes be an issue. This potential phenomena seems to vary platform to platform, or OS to OS - there is no doubt a "hidden" diagnostic table somewhere within the calibration.

    A cable driven VSS pulse generator that outputs at least 40K PPM (some options can go as high as 128K PPM) will operate problem free for all applications, and is a better option.

    That said, you already have an 8K PPM VSS generator - so here is how to set it up. Once operational, monitor TC lockup and slip RPM to determine if your specific application is fully locking the TC - or if there is excessive slip occurring.

    Step 1 - make certain the speedometer cable drive has been properly calibrated for your gear and tire combination. GM cable drive speedometers require the cable to rotate 1000 times per mile. This calibration is achieved by ratio of the number of teeth on the speedometer drive gear (on the transmission output shaft or transfer case shaft), to the number of teeth on the speedometer driven gear (typically mounted to the transmission tailstock or to the transfer case).

    Step 2 - setup the parameters in the PCM software as pictured below. After entering these values, the PCM will accurately interpret the signal from an 8K PPM VSS pulse generator (as long as the speedometer cable is rotating at 1000 PPM). After these changes, you CANNOT use the software to automatically scale the transmission shift speeds - you must now do this MANUALLY - table by table.

    HPT Gen 3 PCM - 8000 PPM Speedometer settings.jpg
    Last edited by Jon S.; 12-08-2019 at 09:17 AM. Reason: typo

  4. #4
    Tuner in Training BrandonHall10's Avatar
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    Quote Originally Posted by B52bombardier1 View Post
    The Dakota Digital Help Desk could answer this question in a nanosecond and explain the mathematics. They were very helpful with my DD HDX set of gauges.

    Rick
    Hadn't even thought of contacting them. Just sent an email to their support desk. Thanks!

    Quote Originally Posted by Jon S. View Post
    When an LS conversion involves a vehicle that uses a cable driven speedometer, generating a useable VSS signal is optimal. There are two readily available means of generating a useable VSS signal to the PCM (computer) - a cable driven VSS generator or a GPS unit that outputs a pulsed VSS signal (Dakota Digital offers both of these options).

    The most common cable driven VSS pulse generators output 8000 pulses per mile (8K PPM), or 16K PPM. These lower PPM rate generators will sometimes cause issues with torque converter going into a fully locked state - excessive slip can sometimes be an issue. This potential phenomena seems to vary platform to platform, or OS to OS - there is no doubt a "hidden" diagnostic table somewhere within the calibration.

    A cable driven VSS pulse generator that outputs at least 40K PPM (some options can go as high as 128K PPM) will operate problem free for all applications, and is a better option.

    That said, you already have an 8K PPM VSS generator - so here is how to set it up. Once operational, monitor TC lockup and slip RPM to determine if your specific application is fully locking the TC - or if there is excessive slip occurring.

    Step 1 - make certain the speedometer cable drive has been properly calibrated for your gear and tire combination. GM cable drive speedometers require the cable to rotate 1000 times per mile. This calibration is achieved by ratio of the number of teeth on the speedometer drive gear (on the transmission output shaft or transfer case shaft), to the number of teeth on the speedometer driven gear (typically mounted to the transmission tailstock or to the transfer case).

    Step 2 - setup the parameters in the PCM software as pictured below. After entering these values, the PCM will accurately interpret the signal from an 8K PPM VSS pulse generator (as long as the speedometer cable is rotating at 1000 PPM). After these changes, you CANNOT use the software to automatically scale the transmission shift speeds - you must now do this MANUALLY - table by table.

    HPT Gen 3 PCM - 8000 PPM Speedometer settings.jpg
    I'll give this a shot next. Thanks for the reply!

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    Quote Originally Posted by BrandonHall10 View Post
    Hadn't even thought of contacting them. Just sent an email to their support desk. Thanks!



    I'll give this a shot next. Thanks for the reply!
    A bit of an old thread, but I have a 6.0L with a 4L80E and an NP208 with the 8k pulse generator. My PCM keeps thinking the transmission is slipping and tripping 0730 fault code. Did you ever figure out your issue? Been trying to figure this out for months on my rig...

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    I have done something similar once before. I can?t remember which sensor I used, whether it was a DD, intellitronix or some combination of oem parts. But I do remember calibrating the speedo gears as close as possible and then playing with hptuners for like a week. When I get home, I can upload the tune of that would be helpful. However, I was using a gen 4 electrical/computer system

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    Tuner in Training BrandonHall10's Avatar
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    Quote Originally Posted by SilverBullet6.0 View Post
    When I get home, I can upload the tune of that would be helpful. However, I was using a gen 4 electrical/computer system
    Sorry. Just now getting back into this after a long hiatus. Yes please share your tune file. Maybe I could glean something from doing a compare.

  8. #8
    Senior Tuner TheMechanic's Avatar
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    Are you trying to fix a speedo problem? Or is it a transmission problem?

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    I'm only replying to this to help someone else in the future as I came across this when I realized I was having this same issue after a test drive. Maybe it was just me, but what fixed my issue with the speedo being off was changing the Sensor VVS Pulses Per Mile to 128,000, which is what my Dakota sensor was set to output (128)....BOOM calibration on dash showed 60mph like it was supposed to during test.

  10. #10
    Tuner in Training BrandonHall10's Avatar
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    4x4 LS Swap w/ Dakota Digital SEN-01-4160 *SOLVED*

    Solved. Updated original post.
    Last edited by BrandonHall10; 06-30-2021 at 11:01 PM.

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    Quote Originally Posted by pilotXC View Post
    A bit of an old thread, but I have a 6.0L with a 4L80E and an NP208 with the 8k pulse generator. My PCM keeps thinking the transmission is slipping and tripping 0730 fault code. Did you ever figure out your issue? Been trying to figure this out for months on my rig...
    Has anyone figured this out? I have the same issue and am new to hptuners just got my 6.0 4l80 swap going in my blazer using the Dakota 8kvss and have the 0730 code also

  12. #12
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    I know this is an old post, but sir.....you are a godsend. A lot of DD VSS information out there is sketchy at best. I tripped over your post, followed your math to the letter......and it worked perfectly the first time out. GPS on my phone was in lockstep with the VSS signal. Because of the angle the VSS sits at coming off the SYE in my Jeep I can't reconnect the speedo cable until I get a 90 degree adaptor, but my OBD gauge shows speed so it's no big deal. Idle issues, DFCO and the exhaust popping on decel issues are all fixed. THANK YOU AGAIN!!!

    speedotab.png
    20230925_110400.jpg