Swapping a Vortec 6.0LQ4 in my 98

[98LimitedLQ4]

I hear you and I would have gotten a 5th gen T4R or a Tacoma if I had the space. Most trackdays should be 2 people and 2 people worth of stuff, but there are some where 2 more of the homies might want to go. Maybe I'll just set a cut off at 2 and be done with it. The last thing I need is some major accident.




Sidenote: Where's OP? I feel like I hijacked his thread but he isn't on here.

I’m just now getting caught up on the replies, I’m still waiting for the Novak mounts and headers to arrive and in the process of cleaning off the Explorer rear axle. The LQ4 will see plenty of abuse both on and off road and a turbo is in the works after it’s all installed and running. Nothing crazy maybe 8-12 pounds of boost. Looking to get a second block and build it all forged for when I add a window to this 6.0. I was told the 8.8 should hold up to 500+hp so I want to get to around there. So the recommendation is a D44 front?
Still have to figure out if I want to keep the Chevys NP electric t-case or swap in the NP242J. Hopefully the mounts get her this week and I can start the swap. I’m definitely keeping the 4L80E, so a 8lb sledge should massage the tunnel? I found a lead on DVB XJ hoods from some guy in AZ. And just going to rework the factory alt bracket to keep the accessory drive intact.

 

[98LimitedLQ4]

hasnt posted since his first post. :dunno:

im wrapping up my 5.3/4L80 swap in my colorado. one thing i wish i had looked into more was the use of the 6L80. i am seeing them more and more in offroad vehicles. gm has had great reliability with this trans in OE applications (not to be confused with the turd 8L80). i would have to look it up in CAD to comment on the width, but i know it is physically shorter than the 4L80, closer to the 4L60 length.

After a couple of days of checking back with no replies I joined a few FB groups so see about some advice, I apologize for the slow response time. The truck I bought was a salvaged truck with the LQ4,4L80e and NP? t-case. Since all 3 work great with 131k miles I would like to just swap in the whole complete assembly if possible.

 

[98LimitedLQ4]

That's great to know. I'm gonna aim for the 8.8. One from ECGS with disc brakes, 4.10 gearing, and a few other bits comes up to ~$2600 delivered. As for the front I'll have to think about that as well but it might wait until fall. I need this built and ready to go by mid/late may.

I pick up 2 used Explorer 8.8 rears with 4.10 and LSD disc brakes, off FB marketplace for $250 each, they will need the perches and shock mounts cut off and new ones welded on. This will be the easier of the rear swaps, the wife’s TJ is getting the 2nd one and will need a truss kit put on but they are pretty straightforward, and the new Miller Multimatic 220 will make short work of the welding.

 

[VAhasnoWAVES]

That's great to know. I'm gonna aim for the 8.8. One from ECGS with disc brakes, 4.10 gearing, and a few other bits comes up to ~$2600 delivered. As for the front I'll have to think about that as well but it might wait until fall. I need this built and ready to go by mid/late may.

ya... for that price id buy a JY axle and a welder. a really ice one. as said, couple shock mounts and spring perches, its pretty easy to do a rear swap. if you are against that idea just stick with an 8.25 swap if you dont already have one.

on the rare occasion that your using the thing in 4wd, just know you cant bounce it off the rev limiter.

 

[cdsurf]

ya... for that price id buy a JY axle and a welder. a really ice one. as said, couple shock mounts and spring perches, its pretty easy to do a rear swap. if you are against that idea just stick with an 8.25 swap if you dont already have one.

on the rare occasion that your using the thing in 4wd, just know you cant bounce it off the rev limiter.

I have the 8.25 in there. This is good news because it means that I can get by with the D30 front and 8.25 rear until next spring. Then I can get stupid and upgrade both. . . and maybe change my lift as well. :laugh:

 

[rockclimber]

I pick up 2 used Explorer 8.8 rears with 4.10 and LSD disc brakes, off FB marketplace for $250 each, they will need the perches and shock mounts cut off and new ones welded on. This will be the easier of the rear swaps, the wife’s TJ is getting the 2nd one and will need a truss kit put on but they are pretty straightforward, and the new Miller Multimatic 220 will make short work of the welding.

If you haven't thought of this yet, you should do your drivetrain swap and any suspension height mods before you weld the perches so you can set the pinion angle correctly

you can tack them in and snug up the ubolts so you can roll it around while you're working on it.

 

[98LimitedLQ4]

If you haven't thought of this yet, you should do your drivetrain swap and any suspension height mods before you weld the perches so you can set the pinion angle correctly

you can tack them in and snug up the ubolts so you can roll it around while you're working on it.

Yeah definitely putting the driveline in prior to the 8.8 going in. I just spoke to the sales team at Novak today, headers are getting shipped tomorrow and the LS swap mounts are next door getting zinc coated so hopefully by next weekend it will all be here and I can start swapping in the motor and trans. After talking with them I may just stick with the 242J for now but he shed some insight if I wanted to go 241c and what wiring I would have to do to the VSS’s. Awesome company to deal with so far.

 

[clydefrog]

What state are you in? I am in CA and the emissions are a pain with motor swaps but def doable. See my build in my sig.

I have been running a D30 and 8.8 since 2014 with my LS swap and 33"s. I have run most of Moab and the Rubicon without any issues, running tru-tracs. Plan on doing a long arm kit to have better clearance with the exhaust. PM me for any other info, i have over 30k miles on my build and pretty much know all the ins and outs and i am extremely well versed on smog.

Modifying your tank is easy, i did a write up on it with pics (see my build)

 

[98LimitedLQ4]

What state are you in? I am in CA and the emissions are a pain with motor swaps but def doable. See my build in my sig.

I have been running a D30 and 8.8 since 2014 with my LS swap and 33"s. I have run most of Moab and the Rubicon without any issues, running tru-tracs. Plan on doing a long arm kit to have better clearance with the exhaust. PM me for any other info, i have over 30k miles on my build and pretty much know all the ins and outs and i am extremely well versed on smog.

Modifying your tank is easy, i did a write up on it with pics (see my build)

I live in Maryland so I will tag this Historic and not have any issues with Emissions or inspections, I would like to delete the EGR and cats and tune out the rear 02 sensors since I don’t need any of that extra stuff. My biggest issue will be tackling the wiring and retaining the factory 98 XJ gauges. I found a trimmed standalone harness from HPI for $319 but don’t know if that is what I need. Novak said I can send in my GM harness and for about $800 they will trim it to work with the LQ4 that I have. Unless it’s a straight plug and play to the Jeep, I’m not convinced that will be money well spent. I appreciate any help or advice you can give. Thanks

 

[VAhasnoWAVES]

I live in Maryland so I will tag this Historic and not have any issues with Emissions or inspections, I would like to delete the EGR and cats and tune out the rear 02 sensors since I don’t need any of that extra stuff. My biggest issue will be tackling the wiring and retaining the factory 98 XJ gauges. I found a trimmed standalone harness from HPI for $319 but don’t know if that is what I need. Novak said I can send in my GM harness and for about $800 they will trim it to work with the LQ4 that I have. Unless it’s a straight plug and play to the Jeep, I’m not convinced that will be money well spent. I appreciate any help or advice you can give. Thanks

turning off VATs, O2s, EGR, etc is very simple with hp tuners. i picked up a refurbed computer with the basic requirements to run the suite for like... $100. youll spend $300 for the MPVI, $100 in credits, another $250 for the pro package if you so choose. but its fun to play with. and i use it to read DTCs all the time.

ultimately youll want someone to tune it once its in the vehicle. so it may be cheaper in the long run to reach out to a tuner to see if they will turn what you dont want, then once you get it running you bring it to them for a dyno or street tuning session. might also be worthwhile welding in bungs for wide band O2s when you are doing the exhaust so they tuner can utilize them. preferably one for each bank, but one after the Y will also suffice.

its worth considering what ECM you intend to use. the truck stuff is big and bulky, but works. i opted for an E40 ECU and a separate TCM for packaging, but that required loading up a start up tune to get things started.

when it comes to harnesses... if you are going to do it yourself, do what you will. LS1 tech is a good resource for figuring things out. but i would rather pay for a new built harness than a thinned down stock harness. a 20 year old harness is likely dry and brittle. a stand alone harness will leave you with 6 wires or so to hook up gauges after plugging it all in, doesnt sound like what you want.

now... getting the factory gauges to work gets complicated, or expensive. you pick. a lot of guys end up just stuffing aftermarket gauges in the factory bezel and being done with it. the issue is getting the GM can bus to talk to the jeep BCM. there is a company that had their LS powered liberty at LS Fest doing passes down the strip. not that it was much of a street vehicle, but they were there to highlight their module they had created to get the GM PCM to talk to the the BCM of other various OEMs.







good news is your not the first one to LS swap a cherokee. plenty of info out there. do some reading, come up with a plan, start getting your feet wet. but keep in mind specific questions get much better answers than generic, "how do i do it?" questions.

 

[98LimitedLQ4]

turning off VATs, O2s, EGR, etc is very simple with hp tuners. i picked up a refurbed computer with the basic requirements to run the suite for like... $100. youll spend $300 for the MPVI, $100 in credits, another $250 for the pro package if you so choose. but its fun to play with. and i use it to read DTCs all the time.

ultimately youll want someone to tune it once its in the vehicle. so it may be cheaper in the long run to reach out to a tuner to see if they will turn what you dont want, then once you get it running you bring it to them for a dyno or street tuning session. might also be worthwhile welding in bungs for wide band O2s when you are doing the exhaust so they tuner can utilize them. preferably one for each bank, but one after the Y will also suffice.

its worth considering what ECM you intend to use. the truck stuff is big and bulky, but works. i opted for an E40 ECU and a separate TCM for packaging, but that required loading up a start up tune to get things started.

when it comes to harnesses... if you are going to do it yourself, do what you will. LS1 tech is a good resource for figuring things out. but i would rather pay for a new built harness than a thinned down stock harness. a 20 year old harness is likely dry and brittle. a stand alone harness will leave you with 6 wires or so to hook up gauges after plugging it all in, doesnt sound like what you want.

now... getting the factory gauges to work gets complicated, or expensive. you pick. a lot of guys end up just stuffing aftermarket gauges in the factory bezel and being done with it. the issue is getting the GM can bus to talk to the jeep BCM. there is a company that had their LS powered liberty at LS Fest doing passes down the strip. not that it was much of a street vehicle, but they were there to highlight their module they had created to get the GM PCM to talk to the the BCM of other various OEMs.







good news is your not the first one to LS swap a cherokee. plenty of info out there. do some reading, come up with a plan, start getting your feet wet. but keep in mind specific questions get much better answers than generic, "how do i do it?" questions.

I’m hoping to reuse the trucks ECU and TCM since I already have them at my disposal, also they are currently working and the truck runs with everything still in place.
A stand-alone harness would be great, I guess the better question I should have asked was, can I piggy back the Jeep ECU to work the gauges and such and tie it into the GM’s ECU?
Finding a tuner to tune on this is kind of a mystery right now, the local LS tuner/dyno shop doesn’t want to touch this when it’s complete.
Definitely will add some 02 bungs when making the new exhaust.
And looking into a atlas 2 speed to get power to the rears.

 

[VAhasnoWAVES]

I’m hoping to reuse the trucks ECU and TCM since I already have them at my disposal, also they are currently working and the truck runs with everything still in place.
A stand-alone harness would be great, I guess the better question I should have asked was, can I piggy back the Jeep ECU to work the gauges and such and tie it into the GM’s ECU?
Finding a tuner to tune on this is kind of a mystery right now, the local LS tuner/dyno shop doesn’t want to touch this when it’s complete.
Definitely will add some 02 bungs when making the new exhaust.
And looking into a atlas 2 speed to get power to the rears.

i think dakota digital is who you want to talk to about this.

 

[Rockwood]

I’m hoping to reuse the trucks ECU and TCM since I already have them at my disposal, also they are currently working and the truck runs with everything still in place.
A stand-alone harness would be great, I guess the better question I should have asked was, can I piggy back the Jeep ECU to work the gauges and such and tie it into the GM’s ECU?
Finding a tuner to tune on this is kind of a mystery right now, the local LS tuner/dyno shop doesn’t want to touch this when it’s complete.
Definitely will add some 02 bungs when making the new exhaust.
And looking into a atlas 2 speed to get power to the rears.

Stock gauges just use the stock computer and install its sensors onto the GM engine. You'll need an adapter for the speedo to work.

 

[Skruffy]

I did a similar swap. LS3 with a 6l80 using Novak mounts. No problem at all with the tunnel clearance. The engine and transmission are actually shorter than the 4.0 with the auto transmission so you will likely need to change your driveshafts.
I have TJ rubicon axles and haven’t broken them, yet.
Gauges were an ass pain but are definitely doable. I spent about half of my time sorting out the wiring and gauges during my swap. The Novak tach emulator worked for me but is very sensitive to voltage during startup. If your battery isn’t totally full it may not function until it has had a minute to charge, then restart the engine. That has been the case for me anyway. I really wanted to retain the stock interior so was a bit picky with this portion, down to the ac switching.
Search supercharged la3 crammed in an XJ on naxja and you can see the whole process that I followed.
The LS is an amazing engine for the XJ and you will be happy when finished. I have somewhere around 500% more horsepower and 75% better fuel economy. You would crazy not to swap the engines given the chance!

 

[cdsurf]

I did a similar swap. LS3 with a 6l80 using Novak mounts. No problem at all with the tunnel clearance. The engine and transmission are actually shorter than the 4.0 with the auto transmission so you will likely need to change your driveshafts.
I have TJ rubicon axles and haven’t broken them, yet.
Gauges were an ass pain but are definitely doable. I spent about half of my time sorting out the wiring and gauges during my swap. The Novak tach emulator worked for me but is very sensitive to voltage during startup. If your battery isn’t totally full it may not function until it has had a minute to charge, then restart the engine. That has been the case for me anyway. I really wanted to retain the stock interior so was a bit picky with this portion, down to the ac switching.
Search supercharged la3 crammed in an XJ on naxja and you can see the whole process that I followed.
The LS is an amazing engine for the XJ and you will be happy when finished. I have somewhere around 500% more horsepower and 75% better fuel economy. You would crazy not to swap the engines given the chance!

Was the AC switching fairly straightforward?

 

[Skruffy]

Was the AC switching fairly straightforward?

It was the only thing that got the best of me. The Jeep ecu knows when the hvac is set to ac. It then writes a pin to ground that allows current to flow to the high and low pressure sensors. If they are satisfied that current makes its way back to the ecu, the ecu then sends current to the ac clutch relay and it engages. The problem I had is that the Novak harness needs the same two circuits. I hijacked the hi/low pressure circuit from the XJ and wired into the Novak harness, this is pretty straightforward. The problem then comes from the ac switch on the dash. The actual physical switch itself is this crazy pneumatic/electric amalgamation so tapping into it there potentially could cause other systems to not work. The other problem is that even if you did the Jeep uses a ground to complete the circuit and the GM uses +12v. So even if you did wire in unless you put in a special relay it wouldn’t work.
So I put a simple 12v button on my dash that feeds the GM ecu 12v when I want the ac on. I didn’t want to do this but was desperate to get everything back together.
The unexpected result was that if the Jeep ac dial was switched to on after 18 seconds the odometer would read no bus. This gremlin took me a while to sort out. Ultimately I took a fused (1 amp) 12v source and fed it to the now unused ac switch sense that satisfies the Jeep ecu and prevents the no bus error.
I have no doubt that there is a way of doing without the added dash switch but I just couldn’t dedicate any more time to figuring it out.

 

[cdsurf]

It was the only thing that got the best of me. The Jeep ecu knows when the hvac is set to ac. It then writes a pin to ground that allows current to flow to the high and low pressure sensors. If they are satisfied that current makes its way back to the ecu, the ecu then sends current to the ac clutch relay and it engages. The problem I had is that the Novak harness needs the same two circuits. I hijacked the hi/low pressure circuit from the XJ and wired into the Novak harness, this is pretty straightforward. The problem then comes from the ac switch on the dash. The actual physical switch itself is this crazy pneumatic/electric amalgamation so tapping into it there potentially could cause other systems to not work. The other problem is that even if you did the Jeep uses a ground to complete the circuit and the GM uses +12v. So even if you did wire in unless you put in a special relay it wouldn’t work.
So I put a simple 12v button on my dash that feeds the GM ecu 12v when I want the ac on. I didn’t want to do this but was desperate to get everything back together.
The unexpected result was that if the Jeep ac dial was switched to on after 18 seconds the odometer would read no bus. This gremlin took me a while to sort out. Ultimately I took a fused (1 amp) 12v source and fed it to the now unused ac switch sense that satisfies the Jeep ecu and prevents the no bus error.
I have no doubt that there is a way of doing without the added dash switch but I just couldn’t dedicate any more time to figuring it out.

I want to cry while reading this. :laugh:


I know it's the part that will get me too, especially since I want to go the route of no Jeep PCM. I would love to do some custom hybrid controller based off diagrams I have for the Jeep HVAC controls but it looks like it would be a nightmare.



So far what I've figured out from the XJ's C3 connector:

• P1 DB/OR wire - A/C Comp. Clutch Relay Control [Output]
• P2 DB/PK wire - Rad Fan Relay Control [Output]

• P13 TN wire - Rad Fan Req [Input]
• P22 DB/WT wire - A/C Switch Sense [Input]
• P23 LG wire - A/C Select Input [Input]

From what you're saying, I'm thinking that:

• P22 was the HI/LO pressure circuit you fed directly to the GM PCM
• P23 was what you had to use a manual switch to replicate for GM PCM/ wired as constant ON for the Jeep PCM
• P13 unused and left for GM's PCM to manage

I may have 22 & 23 switched because my diagram looks like it has a typo but does this seem right to you?

 

[Skruffy]

I want to cry while reading this. :laugh:


I know it's the part that will get me too, especially since I want to go the route of no Jeep PCM. I would love to do some custom hybrid controller based off diagrams I have for the Jeep HVAC controls but it looks like it would be a nightmare.



So far what I've figured out from the XJ's C3 connector:

• P1 DB/OR wire - A/C Comp. Clutch Relay Control [Output]
• P2 DB/PK wire - Rad Fan Relay Control [Output]

• P13 TN wire - Rad Fan Req [Input]
• P22 DB/WT wire - A/C Switch Sense [Input]
• P23 LG wire - A/C Select Input [Input]

From what you're saying, I'm thinking that:

• P22 was the HI/LO pressure circuit you fed directly to the GM PCM
• P23 was what you had to use a manual switch to replicate for GM PCM/ wired as constant ON for the Jeep PCM
• P13 unused and left for GM's PCM to manage

I may have 22 & 23 switched because my diagram looks like it has a typo but does this seem right to you?

Close
P1 and P2 get replaced by the GM harness so no need to worry about them.
P13 is also covered by the GM harness

P22 DB/WT is the one that is satisfied with the constant 12v.
I bypassed p23 because the Jeep effectively uses that as a ground. You will find that it is always 12v regardless of your Hvac switch position. Instead this is the wire that I ran from a 12v source to my dash switch then to the GM harness.
The only good thing about it this way other than it works is that it also acts as a fan request. Push that button and cooling fans come on.
With this set up any time you push it your ac clutch will engage regardless of the XJ Hvac switch position. Not ideal, and not the cleanest but it works.

 

[cdsurf]

Close
P1 and P2 get replaced by the GM harness so no need to worry about them.
P13 is also covered by the GM harness

P22 DB/WT is the one that is satisfied with the constant 12v.
I bypassed p23 because the Jeep effectively uses that as a ground. You will find that it is always 12v regardless of your Hvac switch position. Instead this is the wire that I ran from a 12v source to my dash switch then to the GM harness.
The only good thing about it this way other than it works is that it also acts as a fan request. Push that button and cooling fans come on.
With this set up any time you push it your ac clutch will engage regardless of the XJ Hvac switch position. Not ideal, and not the cleanest but it works.

Interesting. I've thought about it and there may be a solution for pre 2003 PCM's. Cut the LG wire associated with the Jeep's P23 and have it interrupted by a relay's coil pins, then have the relay's switch pins complete a circuit using a 12V source in my case and going to the A/C request wire on the GM ECU. I'm thinking it would be VERY different for you with an E38/E40 ecu since they use serial data.

 

[Skruffy]

I don’t know much about XJs that are older than mine but avoiding the serial CANBUS system is a good way to stay out of trouble. I think your relay plan will work and it will be super satisfying to not need to add a circuit like I did.

Give it a shot!