4.8 Swap LJ

[Shank]

The major reason this project can start is I built a small garage. Plenty of CAD work to meet zoning requirements and fit my atv, mower, and travel trailer plus actually building it later I will be at the point this weekend that I can actually start disassembly. I already have a 5.3 core, 4L60E core, Holley motor mounts will be here tomorrow.

The first project will be reassemble my ATV and insulate the ceiling of my “shed” so I can half ass heat this. Hoping to at least have the fenders and grill off this weekend.

I have done extensive research into what will be required. The 4L60E basically gives you a few options (that I can afford). Run a complete 4L60E to NP231J adapter incorporating VSS in the adapter (clamp on reluctor, as most options are). This is the best way in my opinion but a $6-700 adapter seems wild). Another option is to use an 80’s NP231C front half and Jeep (or chevy) rear. You then use a factory GM 90’s Blazer adapter (this would be for an electronic shift tcase). Issue is you have to add VSS to this adapter or run the adapter on the SYE/tcase (if you run Jeep you have to covert signal to GM and program/wire for low range (ratio difference of 4 low)). This is the cheapest option. Final option is to run aftermarket 4L60E to 4 bolt then a factory GM 700R4 to NP231C with GM front half case.

I have to determine this basically this week.

I plan to pull the drivetrain as soon as I can (full time job thing gets in the way). Hoping by next weekend at the latest. I will then use my core engine and trans as mock up, figure out fitment, driveshafts, etc. I will then have to pull everything and send the 4L60E out for rebuild while I tear into the 5.3.

I will be ditching the Jeep ECM and going aftermarket (planning Marshall gauges with Autometer bezel). I plan to order an in stock new standalone harness and tune the ECM myself with EFILive (more like disable unnecessary factory stuff as I plan to run a bone stock 5.3).

Lot of work ahead but I probably need a project like this.

 

[Shank]

Had a reasonable work weekend between getting parts and two separate nephew’s parties.

Finished insulating the ceiling of the garage and replaced all the fuel lines on my atv.

I then picked up:
-JB Conversions super short SYE
-4L60E (sold to friend bought back)
-NP231C which also had the adapter for a 700R4 that I may need.

I pulled the fenders, grill, and transfer case today. I have almost everything I need disconnected and labeled (actually labeled a lot I don’t need just in case).

Week/weekend plan is:
-Remove engine/trans
-Fit/tack weld (don’t have 220 to garage yet) motor mounts
-Need to determine if AA 50-0405E will clock my tcase correctly and get it ASAP
-Determine what fasteners I need to mate LS driveline together
-Test fit (it AA comes in)

 

[Shank]

Brother stopped over so I couldn’t pass up the help moving the 5.3 into the Jeep garage and pulling the engine and transmission tonight. Plenty of mess to clean up.

 

[Shank]

Surely someone has gone through this and labeled what everything actually does already? I want to know what goes where before I start gutting my factory harness/ECM. I need to get rid of a lot since I will run aftermarket gauges.

 

[Rickyd]

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Surely someone has gone through this and labeled what everything actually does already? I want to know what goes where before I start gutting my factory harness/ECM. I need to get rid of a lot since I will run aftermarket gauges.

You are keeping your factory pdc correct? To me it makes sense to focus on the systems/circuits that will stay until you have what you need.lights,hvac,radio,fuel pump(?),etc. When you have identified everything you'll keep and how to energize their relays without the stock pcm it will be easy to strip stuff like o2 sensors and auto trans.

Using the ignition switch to activate a relay would be an easy way to have a switched ground supply in place of the pcm

 

[Shank]

You are keeping your factory pdc correct? To me it makes sense to focus on the systems/circuits that will stay until you have what you need.lights,hvac,radio,fuel pump(?),etc. When you have identified everything you'll keep and how to energize their relays without the stock pcm it will be easy to strip stuff like o2 sensors and auto trans.

Using the ignition switch to activate a relay would be an easy way to have a switched ground supply in place of the pcm

Yes I plan to keep factory PDC. I need to study up on wiring diagrams to determine what I am trying to accomplish, this will probably be the “hardest” part for me, but sure I’ll figure it out.

 

[Rickyd]

Yes I plan to keep factory PDC. I need to study up on wiring diagrams to determine what I am trying to accomplish, this will probably be the “hardest” part for me, but sure I’ll figure it out.

It's intimidating all together,but if you focus on one circuit at a time it gets much easier.

 

[NovakConversions]

Love it! If you get to northern Utah, let us know! Good luck with the rest of the swap!

 

[Shank]

It's intimidating all together,but if you focus on one circuit at a time it gets much easier.

That basic’s of EE course in college maybe isn’t treating me as well as I hoped. I’ll print the diagrams and study here soon. Good plan for one at a time. I honestly didn’t even know the PCM sent ground to relays for fuel pump. Assuming everything in the PDC is that way but will verify.

 

[Wildman]

That basic’s of EE course in college maybe isn’t treating me as well as I hoped. I’ll print the diagrams and study here soon. Good plan for one at a time. I honestly didn’t even know the PCM sent ground to relays for fuel pump. Assuming everything in the PDC is that way but will verify.

It uses grounds to control the injectors & the replays plus a whole bunch of other things.


All of this is one of the reasons I & others suggest a Magnum for the 97-02 & Hemi for the 03-06 rigs & then if you're going to do the LS you do like @Apparition is planning to do & that is to remove most of the stock electrical.

Reading the Jeep FSM schematics is harder than others. You can get wiring diagrams from AllData offers better ones on some vehicles.

 

[XCRN]

View attachment 590310View attachment 590311

Surely someone has gone through this and labeled what everything actually does already? I want to know what goes where before I start gutting my factory harness/ECM. I need to get rid of a lot since I will run aftermarket gauges.

If you are ditching factory gauges, you pretty much don't need any of the factory 4.0 engine harness. I run factory gauges and the Jeep harness and PCM is pretty much only for the gauges and I used it to control the fan for AC purposes only, but that can be run other ways too. My fuel pump, PCM power and cooling fan is controlled by a standalone harness PDC and I left the starter wiring alone except for adding a ring terminal at the end of the wire.

 

[Rickyd]

It uses grounds to control the injectors & the replays plus a whole bunch of other things.


All of this is one of the reasons I & others suggest a Magnum for the 97-02 & Hemi for the 03-06 rigs & then if you're going to do the LS you do like @Apparition is planning to do & that is to remove most of the stock electrical.

Reading the Jeep FSM schematics is harder than others. You can get wiring diagrams from AllData offers better ones on some vehicles.

I wouldn't toss most of the electrical,just consolidate needed pcm triggered grounds onto an ignition triggered relay.I'd ditch the ASD crap and then decide which circuits I can trigger with a ground and which with a positive. By tapping into the PDC relays to power the body and fuel pump it should come out looking clean.

Basically cut off the head and leave the body. Then find simple ways to turn on the heart etc without needing to totally rewire. That way schematics are still useful.

Thankfully the engine harness will just be b+,b- and switched b+. Depending on what he buys it will control the fuel pump circuit and a few other things as well.

 

[Shank]

I wouldn't toss most of the electrical,just consolidate needed pcm triggered grounds onto an ignition triggered relay.I'd ditch the ASD crap and then decide which circuits I can trigger with a ground and which with a positive. By tapping into the PDC relays to power the body and fuel pump it should come out looking clean.

Basically cut off the head and leave the body. Then find simple ways to turn on the heart etc without needing to totally rewire. That way schematics are still useful.

Thankfully the engine harness will just be b+,b- and switched b+. Depending on what he buys it will control the fuel pump circuit and a few other things as well.

Any suggestions on harnesses? I don’t think I have the time to strip a GM one.

 

[Rickyd]

Any suggestions on harnesses? I don’t think I have the time to strip a GM one.

No,sorry. I converted stock harnesses the couple times I've done these swaps on older rigs.

From what I gather,getting the AC to work can be a challenge. I'd research getting the LS pcm to control the AC somehow. A toggle? The harness and tune I'd get would hopefully support that

 

[Wildman]

Any suggestions on harnesses? I don’t think I have the time to strip a GM one.

There are some LS forums and websites that had a lot of information a few years ago but I honestly never followed them much since I wasn't doing a LS swap. I just remember seeing them pop up.

 

[Shank]

I am pretty stupid when it comes to this, but once I figure one out I’m betting I’ll be fine.

So based off what I’ve read K31 (C8 on relay) is ground. What I am failing to know is how I would know this is a switched ground from PCM besides there is no other ground shown to Fuel Pump Relay. C8 is fused power from inside panel, C10 is battery power, C9 is sending power to pump.

 

[Fluxor]

Maybe a dumb question, I know there are a ton of variables. Does no one make a LS to TJ wire harness? Get X year range LS and use Y harness for basic integration.

 

[NovakConversions]

Any suggestions on harnesses? I don’t think I have the time to strip a GM one.

Maybe a dumb question, I know there are a ton of variables. Does no one make a LS to TJ wire harness? Get X year range LS and use Y harness for basic integration.

We offer a service where you send in the OEM harness from the donor LS and we rework it as well as the LS PCM and send them back ready to integrate into the Jeep. We build it so that the GM PCM communicates with the Jeep PCM, through our module, where needed to retain function of the Jeep gauges and reduce having to go through all the labor or reworking the Jeep harness. With our harness, you end up with 4-6 wires that need to be hard wired into the Jeep or pinned into the Jeep PCM connector, depending upon application.

 

[Shank]

I

We offer a service where you send in the OEM harness from the donor LS and we rework it as well as the LS PCM and send them back ready to integrate into the Jeep. We build it so that the GM PCM communicates with the Jeep PCM, through our module, where needed to retain function of the Jeep gauges and reduce having to go through all the labor or reworking the Jeep harness. With our harness, you end up with 4-6 wires that need to be hard wired into the Jeep or pinned into the Jeep PCM connector, depending upon application.

I have considered this option, I just have had desire to ditch the jeep PCM as they are a known problem area.

 

[Rickyd]

View attachment 590442


I am pretty stupid when it comes to this, but once I figure one out I’m betting I’ll be fine.

So based off what I’ve read K31 (C8 on relay) is ground. What I am failing to know is how I would know this is a switched ground from PCM besides there is no other ground shown to Fuel Pump Relay. C8 is fused power from inside panel, C10 is battery power, C9 is sending power to pump.

If a ground like that goes to the pcm on the actuating side of the relay you can be sure the pcm is switching it. Otherwise it would have no way to function.