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L18 8.1L swap resource thread

wheels87k5

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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.
 
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Larry

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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.
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
p-749-Howell_(5).jpg
 

wheels87k5

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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.
 

ashman

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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.
 

bigblock72

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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
p-749-Howell_(5).jpg

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.
 

SpeedlabDan

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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.
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.
 

NTXJIMMY

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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!!

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Kay86K5

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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
 

NTXJIMMY

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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
 

NTXJIMMY

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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
 

Larry

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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!!

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
46471789635_b5d3a5238f_c.jpg


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

Larry

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Good news for those looking for alternatives for the 12558927 driver’s side high mount A/C compressor and P/S pump bracket. As many have you have found by now, that bracket has become extinct from GM parts for a few years now and used brackets are getting harder and harder to find every day.

Well, necessity is the mother of all inventions! I’ve ran across a talented guy on one of the 8.1L Facebook groups that has created a nice fabricated bracket as an alternative to the 12558927 for use with the Saginaw Power Steering pumps and HT6 (or equitant) air compressors.

Now, some people have reservations about fabricated accessory brackets compared to cast pieces but given the parts availability situation, a fabricated bracket looks pretty appealing to me! I’d also like to add that in the big rig world fabricated brackets are very much the norm even still today. In my world, we use fabricated brackets on Cummins L9 engines in our IC Bus RE series rear engine school buses to mount huge air compressor for HVAC, air compressor for brakes, alternators big as water melons and we never see issues.

As a reminder this is what the 12558927 looks like
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Here is the Amos bracket…
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The next questions with will come to mind is the availability of the matching alternator bracket. As this moment, everything points to the fact GM is still stocking the 12559613 passengers side alternator bracket although Amos has plans to fabricate that bracket in the future as well (and possibly even alternative coolant crossover combinations). There is also the dual alternator bracket 12563070 that has been discontinued by GM although some people have stated a few of these brackets can still be found on dealers shelves from time to time.

Lastly, keep in mind the water pump and crank pulley still must be changed to match this bracket configuration if you’re using an engine from a pick up truck. Part numbers for the water pump and pulley are listed on post #9 on the first page of this thread. Both of those are readily available

If you’re interested in this bracket the contact to have one made is:

Amos Garcia
AmosPGarcia@gmail.com
520-490-0580
8.1l496vortec on Instagram
Amos Garcia on Facebook

:thumb:
 
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Kay86K5

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I saw this on facebook too. I’m planning on picking at least one of these up from him
 

Capt Ron

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I am once again a member of the 8.1 owners club! I picked up what appears to be a 2003 with a claimed 30k miles from a
Schwan's truck. While reading one of ktmoutfront's build threads he mentioned having an 8.1 and I knew he had a cross country move coming up so me being the kind guy that I am I offered to take it off of his hands to lighten the load while moving. After some thought he got back to me with a price and the rest is history. It is missing the injectors and fuel rails so I am on the hunt for those.
I really got to get better at taking pictures.

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ZooMad75

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I am once again a member of the 8.1 owners club! I picked up what appears to be an 2003 with a claimed 30k miles from a
Schwan's truck. While reading one of ktmoutfront's build threads he mentioned having an 8.1 and I knew he had a cross country move coming up so me being the kind guy that I am I offered to take it off of his hands to lighten the load while moving. After some thought he got back to me with a price and the rest is history. It is missing the injectors and fuel rails so I am on the hunt for those.
I really got to get better at taking pictures.

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Nice. It's got the right brackets too. Good pickup. We were probably running north at the same time this afternoon. I was going up 105 instead of I-25 though.
 
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