How to Do a JL Wrangler Hemi SwapLast Updated October 19, 2023 | Andrew Boyle
What happens when you drop a 5.7L Hemi engine inside a seized up JL Wrangler? Well, you'll have to watch CJ Off-Road's JL Hemi Engine Swap YouTube mini-series to find out. The CJ's JL Wrangler has been out of action for some time, and to get it back in on the road, Matt and Brendan have to take out its waterlogged 3.6L Pentastar V6 and replace it with a 5.7L Hemi V8 picked off of a Ram truck.
This is an especially exciting engine swap for the JL Wrangler. With this engine, the JL Wrangler makes more power and has a killer sound to boot. The Jeep Wrangler deserves a V8 engine, so the CJ Off-Road team is simply doing their JL justice. Better yet, the CJ Off-Road video team captures each and every major milestone of the process. If you are interested in seeing an engine swap up close, or you just want to watch some entertaining videos, then this series for you. It is over two hours in length, so this summary can help you find the moments you will be interested in.
Here’s a little bit about this swap, and what it takes to do. There are several other popular engine swaps for the JL Wrangler, but the Hemi engine is particularly more simple to swap in. Given it’s already under the MOPAR umbrella, it doesn't require intense gutting of the JL in order to make it work.
Which Hemis Work in A JL?
First off, the two predominant Hemi engines that can be swapped into a JL Wrangler are the 5.7L and the 6.4L, and this partially due to the work done by the Dakota Customs team providing the conversion kits for these two Hemis. The 6.2L Hemi engine (the revered Hellcat) can be swapped into the JL as well, but takes a fair amount of additional effort.
If you are looking for a Hemi engine to drop into your JL Wrangler, a good place to start your search is in a junkyard. What you’ll want to be looking at are either Dodge Chargers and Challengers from around 2005 or Ram trucks starting from around 2003. CJ Off-Road’s Hemi swap uses an engine found on a Ram truck.
All in all, a 5.7L Hemi swap for a JL Wrangler gives it 395 horsepower and 410 lb-ft of torque. This is a substantial power bump from the JL's 3.6L V6 engine, which makes 285 horsepower and 260 lb-ft of torque.
Keep in mind that there are some physical differences between the Ram and the Challenger/Charger engines that will affect your swap. Things like the harmonic balancer and various cooling lines are different shapes and sizes between both engine variants, so be prepared to cut a bit around the engine bay to make your Hemi engine fit into the JL properly.
These engines can be in various states of disrepair and are frequently a little tricky to fully test in the junkyard lot. If you are concerned about the state of whatever Hemi engine that you might pick, then you could always opt for a Hemi crate engine. While it is more expensive, you don’t have to worry about whether or not the engine will function properly.
In some cases, the stock automatic transmission does not need to be changed for the Hemi swap to work. The Dakota customs conversion kit works just fine with the stock ZF 8-speed automatic transmission found on the JL Wrangler.
What's Needed for a JL Hemi Swap?
There is room to upgrade to the 8HP75 transmission with this swap. This transmission has a higher torque capacity, which is especially critical if you plan on running large tires and off-roading frequently in your JL.
As of now, there are only conversion kits available with the automatic transmission. That being said, Dakota Customs is working on a manual transmission Hemi conversion kit.
There are a variety of things necessary for the JL Hemi swap. Here is what is included in the Dakota Customs kit:
- Bolt on motor mounts
- Wrangler computer reflash (removes engine lights)
- Transmission module flash
- Wiring harness
- SRT headers
- Catback exhaust
- Upgraded radiator
- Custom brackets for the airbox, washer bottle, power steering cooler, a overflow tank
If you want to try to do this whole swap in a DIY manner, then these are the major components that you will need. There are things that aren’t easily done on your own like reflashing the ECU and the transmission module. While it is possible to make or purchase many of the items necessary for the Hemi swap on your own, it is overall much simpler to opt for the conversion kit.
As with any other major automotive project, be prepared to be working on this for a while. Your JL Wrangler could be out of service for several months while the Hemi swap is being performed.
The CJ Off-Road team spent around $15,000 on the swap itself, excluding the price of the JL Wrangler itself and not taking into account the potential labor cost. If you have a JL, plenty of free time, and enough money, then a Hemi swap might not be a bad idea.
Episode One: Intro and JL Teardown
In this episode, Matt and Brendan begin the arduous process of gutting the useless insides of the JL Wrangler. More than anything else, this video shows how much work is truly involved in an engine swap. The hood, grille, front bumper, and many parts of the engine bay are removed during this video. Additionally, this video gives us a peek at how truly muddy the JL's undercarriage truly was.
This episode is also great to hear why the 5.7L Hemi was chosen instead of the darling motor of engine swaps: the Chevy LS. If they were to perform an LS swap, then an entirely new transmission and transfer case would need to be installed as well. Not only is that a lot of extra work and money, putting a GM engine in a Mopar vehicle feels like automotive heresy.
This is the heavy part of the JL disassembly. If you plan on performing this swap yourself, you should keep all of the bits and pieces carefully organized. This entails everything from the electrical connections to the exhaust headers.
Episode Two: Engine Extraction
Now, the old engine is being removed entirely. It's exciting to see the old 3.6 Pentastar V6 and its accompanying transmission get yanked out of the JL to make room for the Hemi. Again, this installation in the Hemi swap series plays out like a careful game of Operation, as Brendan and Matt have to slip the old engine out of the JL Wrangler without damaging any of the other components. The engine itself does seem to come out with minimal fuss, but that pesky transmission takes quite a bit more effort to extract.
This is one of the steps in the engine swap process that is the most finicky. There’s no real trick to it, as the engine and transmission assembly is heavy, large, and full of edges that can catch on parts of the engine bay.
Messes are both made and cleaned up in this episode. The Wrangler's old Pentastar engine decided to lash out once more, leaking a healthy amount of engine fluid onto the floor on its way out. That mess, however, is dwarfed by the cleaning the JL Wrangler receives at the end of this episode. Now that the engine is removed, all of the caked-on mud and dirt can be cleaned out. At this point in the series, the JL is fully prepped for its new heart.
Episode Three: Preparing the Hemi
Now that there's space for the Hemi engine in the JL Wrangler, the engine itself needs to be prepared. In this episode, Matt and Brendan do a variety of things to make the engine ready to be installed. During this time the engine is given a nice new paint job to really make it stand out in the JL's engine bay.
In order to make the transmission work with the Hemi, a conversion bracket is necessary. In order for this to work, a hole has to be drilled in a precise location. Keep in mind, this is a part of the process that is more specific to the Dakota Customs kit itself, not all JL Hemi swaps.
A highlight of this episode is Matt's dense science talk about paint at the nine-minute mark.
Episode Four: Transmission Assembly
Now that the engine is ready to go, it has to be mated to the transmission. This episode has some of the most intense wrenching of the entire series. There are some slight discrepancies with the transmission and the Hemi engine, so in order to get them to fit together correctly (as well as fit in the JL itself) a lot of pieces have to be trimmed and welded.
With the whole engine and transmission assembly is prepared, it's finally ready to go into the JL Wrangler.
There are a lot of fitment concerns depending on which Hemi variant you plan on using for your conversion. Although this is the smaller 5.7L Hemi, it still is the one used on Ram trucks. The nature of this specific Hemi is well suited to the JL Wrangler as typically truck-like grunt is more useful for off-roading and other typical Wrangler activities. This being said, there are a few places were tactical cuts are necessary in order to fit everything nicely under the hood.
Episode Five: Dropping In The Hemi
In this episode, the 5.7L Hemi finally makes its way into the JL. This ultimately plays out like episode two in reverse. After seeing all of the work that went into properly prepping the engine, it's very satisfying to finally see the Hemi nestled inside the engine bay of the JL Wrangler.
The process of getting the engine into the JL is a bit trickier than it was to get the original engine out in the first place. The Hemi pushes the transmission a little farther back into the Wrangler causing Brendan to have to make a few tactical cuts to give it room.
Episode Six: Reassembling the JL
In this episode, many of the smaller tasks required for an engine swap are done. Matt and Brendan in this episode are working down their large checklist and complete tasks like reattaching fuel lines, bolting on various cross members and other engine components that were previously removed.
There are few final details that need to be ironed out when performing a JL Hemi swap. First off, the harmonic balancer from a Ram won’t fit nicely under the hood of the JL, so one from a Challenger or Charger is necessary.
Even though the project is nearing to a close, there are a few narrowly avoided setbacks in this episode. For one, the transfer case got out of sync with the shifter, and an O2 sensor (which was broken in episode one) needed a replacement. Regardless, Matt and Brendan managed to bring it all together at the end of the day.
Episode Seven: Final Odds & Ends
This is the final episode of the JL Wrangler Hemi swap series. There is still some housekeeping to attend to after episode 6, and that all gets taken care here. From installing a higher pressure fuel pump to attaching the slick looking Holley sniper valve covers, this episode finally gives you a full sense of what a beast the CJ Off-Road Hemi-swapped JL Wrangler will be.
It's hard to ignore the infectious excitement that both Matt and Brendan feel in this episode. This project that they were working on for so long is finally coming to fruition. This episode is worth watching just to see their reaction to the JL Wrangler starting up for the first time. It's only a matter of time before they get to really see it in action.
Episode Eight: The Hemi JL's Reveal
Here it is, the Hemi-swapped JL Wrangler in all of its glory. The final product is absolutely stunning. Not only does this JL Wrangler now have a much more powerful Hemi engine, but it is rocking an awesome wrap. In fact, this JL has truly been given a new lease on life given that it was just taking up space before the swap.
Now that you have seen the Hemi swapped JL in action, you ought to keep an eye out for it in both future videos and at whichever events the CJ Off-Roads team attends. This is one of the important members of the CJ Off-Road's vehicular fleet.