Jeep LS swap for the LJ

[RockChucker]

This is looking at the bottom up from the f body pan baffle.

 

[glockman]

This is looking at the bottom up from the f body pan baffle.

That's simple enough, even I might be able to do it. Thank you! The Mast pan seems to be a popular option.

I spent this morning at the junk yard, picking some parts.

My motor has a a return fuel rail, not sure what years don't in the suburbans. The jeeps in 05 and 06 are return less and the stock pump provides enough fuel pressure to run the LS (60ish). So I pulled an injector rail and crossover tube from and 05 truck to get the matching return less rail to tie into the Jeep without capping the return line and creating another potential leak point.

I also picked up an NP241C from a 91 chevy 1500. It's a 27 spline input with 32 spline output and is a manual shifted case. I will loose 4:1 and trade it for 2.7 to 1 but it bolts right to the 4L60E without an adapter and has a GM VSS in the tail housing. If I understand correctly, this should be able to send the proper signal to the GM PCM in both high and low range as the PCM has optional programming for low range from the factory and matches 2.7-1 ratio. All I need is to connect the T case range switch to the PCM to give it the signal, which I believe is ground on pin 16 of PCM connector C2 (green).

Using the 241OR case from my rubi requires a 23 spline output shaft be installed in the trans, an adapter and a VSS, normally installed in the adapter, on the trans output shaft. The adapter with VSS is $600 from Advanced and the labor to put the tail shaft in the trans is probably another $200. I plan to install a JB conversions SYE in my 241C case ($400) and sell my rubi case for north of a grand making this a much more cost effective option. Not sure if I'll regret trading to the higher 4 low gearing, time will tell. I will likely not sell it right away in case I decide it was a mistake.

 

[Gravy]

What have you got in the axles? If it's better than 4.10's I think you'll be alright with 2.72 and 37s. Jon Moore's 1500 Chev turned 315s nicely with 3.73s and your TJ is much lighter. I personally have no love for 4+ tcase gears as my only option. My green TJ has a 4.3 Atlas and it's not enough wheel speed for snow or sand unless I start in 2nd and row my way up to 4th or 5th.

It's surprising how much bigger the NV241C is than a NP/NV231J huh! I tried a 241 in my V8 YJ behind the 700R4 and ended up changing to a 23 spline output instead so I could run a 231J and I didn't have to beat the floor. Although I'm sure you'll be fine since your TJ already has a 241OR... And it's not a YJ

 

[glockman]

What have you got in the axles? If it's better than 4.10's I think you'll be alright with 2.72 and 37s. Jon Moore's 1500 Chev turned 315s nicely with 3.73s and your TJ is much lighter. I personally have no love for 4+ tcase gears as my only option. My green TJ has a 4.3 Atlas and it's not enough wheel speed for snow or sand unless I start in 2nd and row my way up to 4th or 5th.

It's surprising how much bigger the NV241C is than a NP/NV231J huh! I tried a 241 in my V8 YJ behind the 700R4 and ended up changing to a 23 spline output instead so I could run a 231J and I didn't have to beat the floor. Although I'm sure you'll be fine since your TJ already has a 241OR... And it's not a YJ

4.88 gears in the axles. I think it will be OK. I have always hated how the 42RLE combined with the 241OR shifts while in low range. It kicks down to 1rst at the worst time, then immediately jumps back to 2nd and you can't manually lock it into 2nd. It's one of the reasons I looked at the 241C in the first place.

Not related to the LS but I am going to be putting the LJ on a diet this year also. I need to get a "before" weight. It will be interesting to see if I end up lighter with the V8.

I also picked up a drivers side 86 XJ knuckle today to copy DAA's big brake swap. The Passenger knuckle was fighting me and I ran out of time.
Likely won't get the brakes done before the LS but moar powa should always come with moar brakes.

 

[Gravy]

Honestly WJ Akebono calipers are an easier swap with the JKS spacer. I've done two sets before. Makes for better steering.

 

[LSdLJ]

Picked up a superior radiator with trans cooler that I may or may not run and 16" spall fan from a guy with a built LS LJ. It was good to see some different solutions to the swap issues.

View attachment 124252

He was running camaro cats off od Z06 manifolds with pre and post O2s right there. I will likely go this route. This is his setup.
View attachment 124253

I picked up the Z06 manifolds Saturday. The corvettea run egr's so I fabled up some block off plates.

View attachment 124254
Here is the cool thing about the vette manifolds. O2 bungs in the collectors.
View attachment 124255

Also got the block cleaned up and painted and dropped the heads off at the machine shop.
Next on the list is to figure out the last couple harness issues. I've got most of it sorted but need to figure out the A/C control wiring with two pcms.

C6 manifolds not Z06. C6's are the shorter than the Z06's in your pictures. Maybe Z06's will work, but they look long and might interfere with your upper link/driveshaft especially if using the Camaro cats right off the manifold, depending on where link/driveshaft sits. C6's shown in pic.

 

[zmotorsports]

4.88 gears in the axles. I think it will be OK. I have always hated how the 42RLE combined with the 241OR shifts while in low range. It kicks down to 1rst at the worst time, then immediately jumps back to 2nd and you can't manually lock it into 2nd. It's one of the reasons I looked at the 241C in the first place.

I think you will be fine with the 2.72 TC gearing. I had the 241OR in my 2011 JKUR and hated the short shifting when mated with the 42RLE as well. Unfortunately with a 6k pound Jeep even on flat terrain and tires aired down I had to be in 4 LO to keep the RPM's up into the usable power band. Ha, that's funny saying the little 3.8 liter even had a power band.

One thing you will more than likely experience is the fact that 4 LO won't be needed as often as it once was. Many trails I am able to run down them in 2 HI and only shift into 4 LO when climbing over an obstacle or in some instances slowing me when coming down a grade. In those situations such as in sand or soft terrain (snow as well) I prefer the 2.72:1 transfer case to the 4:1 as I can keep wheel speed up. One trail in particular that many may be familiar with is the first section leading up to Gemini Bridges and Metal Masher after leaving Hwy 191 in Moab. That first switchback section after leaving the pavement is quite steep and I used to have to be in 4 LO just to get up that grade and not overheat the engine or the transmission. The last two times we were in Moab this year I experimented and stayed in 2 HI and monitored engine and transmission temperatures and I was able to climb right up in 2 wheel-drive switching between 1st and 2nd gear with engine temps staying at or under 210-degrees and transmission temperatures staying under 165-degrees. It's like cheating.

When climbing over obstacles I thought I may miss that 4:1 but it turns out with so much more low end torque, a lower first gear in the transmission and my 4.56:1 gearing the 2.72:1 TC gearing is actually perfect for my application.

The researching phase and parts acquisition phase seem to be the most stressful. Once you move past that and enter the actual "installation" phase the fun begins, especially seeing the homework pay off.

Mike

 

[zmotorsports]

Also, on a side note, I did the same thing as you and sold my 241OR transfer case to someone with a Sport and wanted the 4:1 ratio. It sold quickly on ksl.com.

Mike

 

[Gravy]

Here the spacer.

WJ Steering Conversion Knuckle Flange Spacer | Jeep Wrangler TJ and LJ, Cherokee XJ and Comanche MJ

Properly install the WJ steering knuckle with a WJ Steering Conversion Knuckle Flange Spacer for your Jeep Wrangler TJ and LJ, Cherokee XJ and Comanche MJ

jksmfg.com

Better Brakes & Steering for Our TJ Wrangler - Four Wheeler

We add a combination of junkyard parts and aftermarket components from JKS and Skyjacker to upgrade our Wrangler steering and brakes.

www.fourwheeler.com

I like it because this swap gives you real crossover steering.

I've done 2 sets of these swaps about 11 years ago and the more desirable caliper on WJs (there are 2) are made by Akebono and really great. My current TJ has crossover like this and it is one hand steering even at 85mph.

 

[glockman]

C6 manifolds not Z06. C6's are the shorter than the Z06's in your pictures. Maybe Z06's will work, but they look long and might interfere with your upper link/driveshaft especially if using the Camaro cats right off the manifold, depending on where link/driveshaft sits. C6's shown in pic.


View attachment 124331

Ya I found the difference yesterday. I'll have to see how they work. They are way shorter than the truck manifolds. After pricing Camaro Cat's (close to $200 a piece) I am considering some universal small cat's that I can tuck in however I need to.

I think you will be fine with the 2.72 TC gearing. I had the 241OR in my 2011 JKUR and hated the short shifting when mated with the 42RLE as well. Unfortunately with a 6k pound Jeep even on flat terrain and tires aired down I had to be in 4 LO to keep the RPM's up into the usable power band. Ha, that's funny saying the little 3.8 liter even had a power band.

One thing you will more than likely experience is the fact that 4 LO won't be needed as often as it once was. Many trails I am able to run down them in 2 HI and only shift into 4 LO when climbing over an obstacle or in some instances slowing me when coming down a grade. In those situations such as in sand or soft terrain (snow as well) I prefer the 2.72:1 transfer case to the 4:1 as I can keep wheel speed up. One trail in particular that many may be familiar with is the first section leading up to Gemini Bridges and Metal Masher after leaving Hwy 191 in Moab. That first switchback section after leaving the pavement is quite steep and I used to have to be in 4 LO just to get up that grade and not overheat the engine or the transmission. The last two times we were in Moab this year I experimented and stayed in 2 HI and monitored engine and transmission temperatures and I was able to climb right up in 2 wheel-drive switching between 1st and 2nd gear with engine temps staying at or under 210-degrees and transmission temperatures staying under 165-degrees. It's like cheating.

When climbing over obstacles I thought I may miss that 4:1 but it turns out with so much more low end torque, a lower first gear in the transmission and my 4.56:1 gearing the 2.72:1 TC gearing is actually perfect for my application.

The researching phase and parts acquisition phase seem to be the most stressful. Once you move past that and enter the actual "installation" phase the fun begins, especially seeing the homework pay off.

Mike

Great info. I really hate the 42RLE. Did I mention that yet?

Here the spacer.

WJ Steering Conversion Knuckle Flange Spacer | Jeep Wrangler TJ and LJ, Cherokee XJ and Comanche MJ

Properly install the WJ steering knuckle with a WJ Steering Conversion Knuckle Flange Spacer for your Jeep Wrangler TJ and LJ, Cherokee XJ and Comanche MJ

jksmfg.com

Better Brakes & Steering for Our TJ Wrangler - Four Wheeler

We add a combination of junkyard parts and aftermarket components from JKS and Skyjacker to upgrade our Wrangler steering and brakes.

www.fourwheeler.com

I like it because this swap gives you real crossover steering.

I've done 2 sets of these swaps about 11 years ago and the more desirable caliper on WJs (there are 2) are made by Akebono and really great. My current TJ has crossover like this and it is one hand steering even at 85mph.

I just replaced ALL of my Currie steering. I'm not really apt to replace it again. Carl laid the WJ stuff out really well and I have just not wanted to cut off all my factory stuff. It might seem strange but it works pretty well as is. DAA's upgrade requires way less fab work.
I will be more than happy to chat with you while you fab up a WJ steering for me now that you're injured

 

[DAA]

You do get bigger rotors with more swept area than WJ with the XJ knuckle/Mercedes rotor/WK2 caliper.

- DAA

 

[RockChucker]

Ya I found the difference yesterday. I'll have to see how they work. They are way shorter than the truck manifolds. After pricing Camaro Cat's (close to $200 a piece) I am considering some universal small cat's that I can tuck in however I need to.

If you are able to make OEM cats work, I would recommend going that way. When I did my exhaust, I used some small high flow magnaflow spun cats. They were compact and I was able to fit both of them by the trans (AX15 initially remember). After 1 year, I started getting cat inefficiency codes. They weren't working sufficiently anymore. Found that is pretty common. An OEM cat will work much better and last years. The up front cost might be higher, but lower overall in my opinion.

 

[glockman]

If you are able to make OEM cats work, I would recommend going that way. When I did my exhaust, I used some small high flow magnaflow spun cats. They were compact and I was able to fit both of them by the trans (AX15 initially remember). After 1 year, I started getting cat inefficiency codes. They weren't working sufficiently anymore. Found that is pretty common. An OEM cat will work much better and last years. The up front cost might be higher, but lower overall in my opinion.

I'll have to see if I can find a better source for the OEM cat's. I only looked briefly and had some sticker shock. Thanks for the info.

 

[glockman]

I picked up a 2005 corvette oil pan that has baffles from the factory. Better yet, I got it for $50 with pickup and windage tray. Not sure what dipstiick will work with this combo. I also picket up the smaller corvette manifolds from the same guy.



Oil pan is on so I installed the no return fuel rail. Only used the drivers side rail and crossover tube to get ride of the return but the fuel rail doesn't quit sit flush. I think it's just a tab thickness, injectora are fully seated.

This is the passenger side with the original rail


With progress stopped waiting for heads from the machine shop, I started tackling the snake.

 

[XJEEPER]

Honestly WJ Akebono calipers are an easier swap with the JKS spacer. I've done two sets before. Makes for better steering.

Words of truth. I did the WJ knuckle swap on my XJ about 9 yrs ago and also moved the steering linkage OTK. Zero regrets and it brakes and steers awesome.

 

[glockman]

Got most of the harness stripped and re-loomed. There are a couple issues I still have to clarify but all the excess sensors and wires have been removed and the stubs are all laid out. A couple of notes for those interested.

My harness is an 03 or 04 (not 100% sure) and was complete with all wires still connected to the engine and the power stubs still on the C2 power block from the GM under hood fuse block.

In an LS swap, there is the C2 power block, the two PCM connectors (C1 and C2, blue and green in my case) and the other end of every wire goes to a plug that connects to a sensor. You basically start at the PCM and power block and pull the unneeded wires out and trace them back to the sensor that is being removed, ie A/C signals, coolant level, oil level.

I am attempting to use all the emissions equipment (evap purge soleniods) and all 4 O2 sensors. Other than these two issues, I mostly followed the video on the LT1SWAP youtube channel. I would recommend you watch them all at least 3 times if you are thinking about doing this. The video really does make it super simple for a gen 3 swap. Granted I'm not finished and it isn't running yet.

I'll detail a couple of the hiccups I've had. Most of them are caused by forgetting that this is a stand alone 4 wire harness. There are many circuits in the Jeep that will replace items in the GM harness. I kept getting side tracked and trying to figure out how they would need to be ran.

For instance, all the starter wires are removed from the GM harness, except one. I will use the jeep wire from the ignition switch to fire the jeep starter relay that will have one wire from the LS harness connected directly to the solenoid on the starter. There are several wires in the PCM that are related to starting, you need none of them, only the purple wire from the C2 power distribution block on the LS harness, connected to your jeep starting relay.

Basically, you need a couple 12v constants, a couple ignition switched 12v and ground. The rest is gauges, fans and 4WD. Remember, the LS will run on its own aside from those few wires. Here are some other notes that might help someone else in the future.

I am using pin 16 from the green (C2) connector to tell the PCM I'm in Low range to correct shift points for gearing through the factory GM 4wd table. This is should work since I am using a GM transfer case with 2.71 :1 low. I'll try to find an OEM mate to the plug on the T-case. It's a two wire plug which I assume is one signal and one ground that are tied together when in low range. This is a main source of debate on the 5.3 swap threads. Where to put the VSS and which one to use, Jeep or GM. I hope my plan works.

My harness has the new style transmission range selector connector. I am using pins 4,5,6,7,8 to tell the PCM what gear the trans is in. These are Transmission range signals A, B, C, Grnd and P (parity). Pin 10 will be used to power the reverse lights and pins 11 and 12 are tied together to ignition power. I had to look for a while to find this. I pulled the other wires from the transmission range plug and the harness.

I am running an electric, single speed fan. I hooked it to C1 (blue) connector pin 42. LT1Swap shows this as low speed but I think it works either way with a single speed fan, it just needs voltage, there is either on or off, no variable voltage for speed. To get high speed, you connect the high speed signal to a second fan.

I removed all the A/C controls from my LS harness and will run the A/C from the Jeep PCM. I think this is possible and the easiest method.

I am going to try and use the Jeep PDM to power the LS circuits so I don't have to use an auxiliary fuse panel and relays. I think there is enough space after removing the Jeep engine control items.

 

[RockChucker]

I am using pin 16 from the green (C2) connector to tell the PCM I'm in Low range to correct shift points for gearing through the factory GM 4wd table. This is should work since I am using a GM transfer case with 2.71 :1 low. I'll try to find an OEM mate to the plug on the T-case. It's a two wire plug which I assume is one signal and one ground that are tied together when in low range. This is a main source of debate on the 5.3 swap threads. Where to put the VSS and which one to use, Jeep or GM. I hope my plan works.

I don't see why this method wouldn't work. When I swapped my 4L80 in, I specifically chose an early 4L80 because it has a speed sensor on the input and output shaft. My tcase wouldn't be a good candidate for trying to manage a 4wd shift table for the trans. First, it has 2 different low ranges (neither matching 2.72:1) and second, it doesn't have the necessary 40(?) tooth reluctor wheel or a way to accept the GM speed sensor. My trans always thinks it is in 2wd, and I haven't ever had any issues with shifting while in low range.

 

[zmotorsports]

Great job on the wiring as that seems to be the most intricate part of the entire swap. For your A/C system you may want to see if you can locate the input terminal on the GM side (ECM) and provide a signal to that so you get the A/C bump in your idle right from the A/C controls to the GM ECM rather than what most do and simply rely on the GM ECM seeing a drop in RPM and then correcting through the throttle body via the ECM.


It's basically two ways of accomplishing the same thing but letting the A/C demand control RPM through the ECM is the OEM manner used and definitely more seamless, I don't even feel the RPM change when I kick the A/C on.

Also when finishing up your wire loom keep it as OEM appearing as possible using the same connectors especially but also the same split loom and wire wrap if you intend to be USEPA compliant. The testing agency looked very specifically at my wiring harness when I went for my emissions certification.

Mike

 

[glockman]

Great job on the wiring as that seems to be the most intricate part of the entire swap. For your A/C system you may want to see if you can locate the input terminal on the GM side (ECM) and provide a signal to that so you get the A/C bump in your idle right from the A/C controls to the GM ECM rather than what most do and simply rely on the GM ECM seeing a drop in RPM and then correcting through the throttle body via the ECM.


It's basically two ways of accomplishing the same thing but letting the A/C demand control RPM through the ECM is the OEM manner used and definitely more seamless, I don't even feel the RPM change when I kick the A/C on.

Also when finishing up your wire loom keep it as OEM appearing as possible using the same connectors especially but also the same split loom and wire wrap if you intend to be USEPA compliant. The testing agency looked very specifically at my wiring harness when I went for my emissions certification.

Mike

Great advice! The A/C control makes sense and should be easy. I'll take a look.

I plan to try and make the install as factory looking as possible for my benefit, good point about the inspection though. If they can't tell what's changed its harder for them to scrutinize it.

 

[zmotorsports]

You may already know this but just FYI in case others are reading this and looking to do a similar swap.

Since you're reducing wire count in your loom be very cautious of ground wires. Do not eliminate or combine grounds. GM had some issues early on as they were transitioning from their Gen III to Gen IV engines and electronics where they used a common ground. With their earlier iterations it wasn't an issue but with the more sensors they were adding and relying on for data as well as multimale servos such as throttle body, purge, etc. they quickly realized that one ground wasn't enough of a current path and were experiencing limp mode symptoms. This was solved by adding multiple grounds but unfortunately one of the more common things I've seen when people try to reduce wire count is these grounds being combined. Even on some aftermarket standalone wiring harnesses for street rods/race cars I see this and it is not a good practice because if several servos are being activated it can cause just enough of a voltage drop to put the ECM into limp mode. These systems are monitoring so precisely that even a few millivolts of voltage drop or out of parameter and it will either throw a code or worse put it into limp mode. This is also why the USEPA guidelines specify that even the factory wire harness must be intact as it is an integral part of the emissions system nowadays.

Just an FYI.

Mike