L18 8.1L swap resource thread

Discussion in 'The Engine Bay' started by Larry, Jun 14, 2013.

  1. wheels87k5

    wheels87k5 24 Karat Premium Member GMOTM Winner

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    This is what I'm needing to find out. If what I have now will not work like needed, what do I need to do to correct it?

    Do I need to add something to the NP241 so that it will be in sync?

    Since my NP241 is the mechanical speedometer, will I need to convert it to electrical?

    Maybe it's best to put this in the Garage section.
     
    Last edited: Jan 15, 2019
  2. Larry

    Larry 1/2 ton status Premium Member GMOTM Winner Author

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    Sorry for the late bloom as my laptop threw a rod and I have been confined to watching from afar on my phone. It is my understanding the two speed sensors on a 4L80E are to measure turbine speed and slip or something like that. You would still need a speed sensor on the actual output of the transfercase to work correctly. Howell Engine Development sells a speed sensor that screws into the speedo cable port to gain a VSS signal. You're in good hands working with Team208 so you probably aught to get with him and get his imput on that question. I don't mess with automatics to be able to give good solid advise

    Not sure if something like this would work or not but I'd research this before digging into a VSS swap on your 241
    [​IMG]
     
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  3. wheels87k5

    wheels87k5 24 Karat Premium Member GMOTM Winner

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    OK...thanks for the input. I just sent Howell the question at hand.

    I also started a thread on this in the Garage.
     
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  4. ashman

    ashman It's not a bronco Premium Member GMOTM Winner

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    Dakota digital makes an adapter to get vss from a mechanical speedo as well. I used it for awhile and it worked great. Only like $30 too.
     
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  5. bigblock72

    bigblock72 Elmer's glue taste tester Premium Member GMOTM Winner

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    You don't need to have the VSS read at the transfer case, the output speed sensor in the trans will do everything that you need and you will be able to keep the original mechanical speedo. My Blazer has been this way (and most of the swaps I do) for many years with no problems, in fact I like having the converter lock up in low range 20 mph as it helps keep the trans cool. The only negative about not having the VSS in the t-case is the trans shifts a little slow when in low range, but it certainly isn't a deal killer, I'm just a little easier on the throttle.

    When using a 4l80-70-65-60e trans you must have a 40 pulse signal for the computer to be able to shift the trans properly. All of the speedo cable sensors are less than 8 pulse and work fine for a manual trans or old school automatic transmission.
     
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  6. SpeedlabDan

    SpeedlabDan Keepin it trashy never classy Premium Member GMOTM Winner

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    I agree I'd rather have the. Vss in the body of the trans not the tcase. For my Allison it would fix the low range issues especially having double low and come to think of it if I drop the rear shaft I would have no vss signal in front drive hi/low. Now if I cold just figure out where to put the vss in a 4wd trans.
     
  7. NTXJIMMY

    NTXJIMMY Now that's thinking with your dipstick JIMMY! Premium Member

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    Larry
    Great info! I appreciate all the support for this

    I recently purchased a ‘88 K30 Crew Cab and a workhorse 8.1 in the pics below

    I have a quick question and I might have skipped over it somewhere in the thread but here it goes

    When you swap the drive by wire to the 7.4 drive by cable throttle valve What brackets are you using for the throttle and cruise cables ?

    Thanks!!

    BC18097B-9A6A-4C86-A2D1-2FCDFB7BCCB8.jpeg

    53377725-6E45-4B3C-B70D-35C896F34CA0.jpeg

    658BE459-9F68-404A-8395-3326FD05C745.jpeg
     
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  8. Rick Capito

    Rick Capito Newbie Premium Member

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    I made my own . Welcome to the 8.1 club IMG_0927.jpg IMG_0926.jpg IMG_0926.jpg
     
  9. Kay86K5

    Kay86K5 1/2 ton status Premium Member GMOTM Winner

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    On my old 8.1 that I was using mech throttle on, I actually just picked up a throttle cable and throttle bracket from a 97 Tahoe with a vortec 5.7, and then modified the bracket just a tad, and bolted it to the same intake bolt as shown just above. Seemed to work just fine
     
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  10. Larry

    Larry 1/2 ton status Premium Member GMOTM Winner Author

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    Yeah, I just made cable brackets too. Don't have access to any pictures at the moment but can try to get some tomorrow
     
  11. NTXJIMMY

    NTXJIMMY Now that's thinking with your dipstick JIMMY! Premium Member

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    Thanks guys
    I think I have one or 2 of the 5.7 Vortec brackets laying around I will see what I can do with those

    Anybody have more pics I would greatfully appreciate them.

    I will start a build thread on this one as soon as I start on it and get done with my Jimmy.

    Right now gathering parts
     
  12. NTXJIMMY

    NTXJIMMY Now that's thinking with your dipstick JIMMY! Premium Member

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    Wondering if this would work

    Holley 20-147
    Summit sells it for $33
    Just wondering if it would work with the 8.1 due to the angle of the throttle valve


    E7BED1F2-38DF-4886-84A6-990CFC6D5C28.jpeg
     
  13. Larry

    Larry 1/2 ton status Premium Member GMOTM Winner Author

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    Both bueno... the 8.1 has a three bolt throttle body
     
  14. Rick Capito

    Rick Capito Newbie Premium Member

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    And as Larry said in his article you'll need a throttle body spacer at least I did.
     
  15. Larry

    Larry 1/2 ton status Premium Member GMOTM Winner Author

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    Back home finally. Here are some cable bracket pictures from mine.

    This one is the K10. Both trucks use a Lokar TC-1000LS1U throttle cable
    [​IMG]

    [​IMG]



    Suburban
    [​IMG]




    Exactly, mine needed the throttle body spacers in order to route the cable in the most direct and smooth fashion as possible. Others have commended on FB groups they were able to use the L29 TB without a spacer but I haven’t seen pictures or how they’re routing their cables. They must be routing them very low and around the fuel rail with a ton of curves and potential bind spots
     
  16. NTXJIMMY

    NTXJIMMY Now that's thinking with your dipstick JIMMY! Premium Member

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    Thank you guys for the info!
     
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