Mdmike's mall-tastic Hemi powered LJ

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    Mdmike's mall-tastic Hemi powered LJ

    I figured since it's so easy to upload pics now, I would toss up a mini build thread on my mall-crawler/daily driver LJ. I know a Hemi swap in a TJ/LJ isn't exactly "hardcore" tech (especially for a Jeep like mine), but as I was researching this project, there were quite a few questions I had that were coming up empty on internet searches. Hopefully this little thread might help someone else in the future.

    So, a few years ago, my buddy that owns Appalachian Offroad here in Maryland told me he came across a deal on a high mileage LJ. Since he was already neck deep in his own projects, he agreed to pass the deal on to me. I made him an offer he couldn't refuse, and a 269,000 mile 4.0/6 speed LJ showed up in my driveway. It was filthy, a little rusty here and there, but still ran really well for having nearly 300k.
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    I did the usual lift/regear/rims/tires and put another 10 thousand or so miles on it knowing I should be keeping an eye out for a low mileage 6 cylinder to replace the tired 4.0. I also managed to scoop up a hard top in the mean time, which I was really excited about.

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    Fast forward to that winter and I get a call from my Sister telling me a guy slid through an intersection in an ice storm and hit her Grand Cherokee, totaling it. Thankfully she was ok, but the Jeep took a pretty good hit. The gears in my head started turning, 1 thing led to another, and I bought her Grand back from the insurance company. Her Jeep had just turned 100k miles and I know her and my BIL had taken good care of it throughout its life. The damage was mainly the front passenger fender and core support, and it still ran and drove.

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    On to the wrenching:

    Here is where the Hemi started life:

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    I was surprised at how much of a pain in the ass it was to extract this thing!

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    Engine and transmission out and strapped to the table.
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    I parked the new drivetrain next to the Jeep hoping nature would take its course and it would just hop in there, but sadly that wasn't the case.

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      It was waiting for the shoe horn
      I like popsicles.


        At this point it was the LJ's turn to go under the knife

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        The parts pile just kept growing.

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        So, this is the most important part I needed at this point:
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        That is the under hood engine wiring harness and fuse box from the LJ. Before I started this project I called a couple of the reputable Hemi swap specialists to figure out exactly what I was going to need to get the wiring harness squared away. The 1st place I called told me I needed to sell the Grand Cherokee engine and buy a truck motor instead My next call to Chris at Hotwire Auto was far more productive. He basically told me to box up this harness, send it to him, and it a few weeks an all new harness would show up that would be plug and play.

        Edit to add: the other necessary component of the wiring harness is a 2005 Dodge Ram Hemi truck ecu. I got mine off of ebay for less than $100.

        So, I boxed everything up and shipped it off and that is when the clock started ticking. At the time, I think Hotwire's lead time was about 3 weeks to get the harness done, so I was on a mission to get the new drivetrain installed.
        Last edited by mdmike; 06-03-2020, 11:49 AM.


          First up was getting the new drivetrain in the Jeep. The go-to for Hemi swap motor mounts in a TJ/LJ is Advanced Adapters and they make life VERY easy. First things first, the stock 6 cylinder mounts have to go

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          AA supplies you with a little fixture to get the mounts exactly where they need to be. You pop your brake line bracket out of the frame and use the existing hole for their fixture. Then, you butt the new Hemi mount up to it, and weld it on. Super easy.

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          For the transmission mount, I used a part from Teraflex. This allows the 545rfe trans to mount to a skid plate in the stock position. It is their part# 4947183

          What I didn't realize at the time, is that the AA motor mounts and the Teraflex transmission mount locate the drivetrain a few inches taller than the stock mounts. I ended up with a Rough Country "belly up" skid plate and still had to put 1" spacers between the mount and the skid plate.

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          So here is a little bit of tech for the thread. The tail housing on the Grand Cherokee has a different bolt pattern for the transfer case. Luckily there is a Mopar part that solves the problem. It is part# 52107719AC. You will also need 2 seals as well, part# 4799090 and part# 501902ab. I got the tail housing from ebay for less than $100.


            At this point, the drivetrain is in and I started going after each "system" individually.

            The first thing that gave me a hard time was the steering. The Grand Cherokee uses a hydraulic cooling fan that is run off of the power steering pump. Because of this, the pressure line is a bigger diameter than the stock line on LJ. I had read about other guys getting custom lines made, but I was trying my best to use off the shelf parts. My first attempt was a truck pump with the integrated reservoir, but that didn't even come close to fitting properly. After some digging, I found that the power steering pump on the Hemi Dodge Chargers mounted to the engine perfectly, but used the smaller diameter hoses that matched the LJ. I was able to creatively re-route the stock pressure line from the LJ and it bolted right up to the box. For a reservoir, I bought the factory piece from a Charger and made a bracket to mount it to the driver's side fender. I was even able to reuse the stock return line from the box to the reservoir, and a line scavenged from the Grand Cherokee to go from the reservoir back to the pump. Unfortunately I don't have any pics of the way I routed the line, but you can see my reservoir location in the bottom/right of this pic:

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            Next up was fuel. Luckily, the 05-06 fuel pumps have enough pressure and volume to keep the Hemi happy. I figured since the pump in the Jeep could potentially have 270K miles on it, a replacement was in order. I swear, every time I need to do a fuel pump, the tank is full.

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            With the pump done, I had to address getting fuel to the engine. The line from the hard line to the fuel rail on the Grand Cherokee is a bigger diameter than the stock line on the LJ. After some research, I came up with these 2 fittings to get the job done (Vibrant Performance part#'s VPE-16445 and VPE-16881) I had to gently bend the stock hard line to get it where it is, and by flipping the stock flex line from the Grand Cherokee around backwards, it lined up perfectly.

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              On to the exhaust. Regardless of which Hemi you're putting in a TJ/LJ, you need to use the stock exhaust manifolds from a Grand Cherokee. I noticed 1 broken manifold bolt when I got the motor out of the Grand, so I decided to replace both manifold gaskets and address any future problems with broken bolts while the engine was out. I bought a replacement manifold bolt kit, tap, and got after it.

              Talk about a great time!

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              If you've ever broken a tap off in a hole, THIS is what victory looks like!!

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              With that done, it was time to get the exhaust out the rear of the Jeep. I had read another build thread on a different forum and knew the Grand Cherokee down pipe and cats bolt onto the LJ almost perfectly, but due to the way the front driveshaft on the IFS Grand Cherokee runs to the front dif, it puts the driver's side down pipe right in the way of the LJ front driveshaft. I had never done "custom" exhaust work before, so I figured I'd give it a go. I needed some reaaaally tight bends where the downpipe comes off the manifold, and then down at the converter. I took a piece of exhaust tubing and cut a bunch of 15 degree bends and started taping/tacking the exhaust together until I got it to fit. Then, at the rear I lobbed the flange off of the Grand Cherokee down pipe and welded the flange from the LJ exhaust to it. This exhaust bolts right up to any aftermarket cat-back system. I'm running Banks cat back on it now and it sounds great. I was expecting it to be really loud, but it is surprisingly quiet.

              Not my finest work by any stretch, but it clears everything and doesn't leak. I had been "encouraged" by some friends to throw some exhaust wrap over this part of the pipe, but I own this one 100%.

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                Cooling was up next.

                I found a Hemi swap radiator on ebay from Superior Radiator and decided to go with a new Ford Taurus fan. I built some brackets to hold the fan off of the radiator and bolted everything in together

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                I was able to cut and sleeve the stock Grand Cherokee upper hose and it worked out good

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                The lower hose got the same cut/sleeve treatment, but I had to use some heat and a big socket to get the diameter of the hose over the radiator inlet

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                The radiator came with a bung welded in for a fan thermostat switch, which was really convenient. The wiring harness from Hotwire comes with a powered 12v wire for an electric fan, but the computer does not tell the fan when to come on, unlike an LS swap computer would. I bought a 200* on/185* off fan controller that works well:

                I also addressed the transmission cooler too. I bought a simple plate style cooler from the local auto parts store, welded some tabs onto the support rods in the grill/in front of the radiator, and mounted it up. I was able to use the stock Grand Cherokee transmission cooler lines all the way up to the grill. I cut them there and used rubber hose up to the cooler. Super easy.


                  There were some other odds and ends that needed done too.

                  Shifters: I got VERY lucky with this. My buddy that runs the offroad shop had a customer come in and want a manual trans swapped into his automatic LJ. The stock automatic shifter and shift cable work perfectly with the 545rfe.

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                  The transfer case shifter wasn't quite as easy. I tried every which way to get the stock mechanical linkage to work, but failed. I ended up buying a cable shifter setup and it made life a lot easier.

                  The Hemi is a "drive by wire" setup. Luckily, the go-to pedal for the install is the Grand Cherokee pedal assembly. Teraflex makes a bracket that makes it a bolt in deal. Part# 4877480

                  The other thing that needed addressed was the steering shaft. The Advance Adapters driver's side engine mount comes with a bracket welded to it to accommodate a stock 4 cylinder TJ steering shaft bracket. This bracket keeps the steering shaft out of the exhaust. I got a used one from a junk steering shaft my buddy had laying around.

                  With everything working mechanically, it was time to make things look pretty so the drivetrain came out 1 more time.

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                  Last edited by mdmike; 06-03-2020, 11:58 AM.


                    Cleanup and painting done, and the drivetrain went back in for the last time
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                    The day finally came and this big box of awesome showed up

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                    The harness from Hotwire is simply a work of art. They start with a brand new Mopar harness and everything fits perfectly. The harness lays on the engine perfect and everything lands right where its supposed to. Yes, it is expensive, but you realize its worth every penny once you put your hands on it. The only other wiring you need to do yourself is the charging wire for the alternator to the battery and the battery to the starter. I was able to reuse the wiring from the Grand Cherokee and it worked out well.

                    Initial startup was the most anticlimactic event. I hooked up the battery, hit the key, and it fired up instantly and idled perfect. The factory gauges worked perfectly with the Hemi too.

                    I did end up with 2 engine codes right out of the gate. One was for the downstream 02' sensor on the driver's side, which was an easy fix. The second one was the ECU not recognizing the ignition key, and proved a little more troublesome. Technically, the vehicle shouldn't run if it doesn't recognize the "security key", but (I assume) Hotwire programs that feature out of the ECU. The problem with that comes at emissions testing time. In MD, you can not have a CEL on in order to pass. Luckily, there is a shop local to me that was able to program my key to the ECU. Hotwire programs your vin number into the ECU, but you need an additional 4 digit code from Mopar to make the computer pay attention to the key and turn the light off. One option is to go to the dealership and have them do it for you under the guise of having installed a new computer.

                    Now, I'm not sure if this story is true, but the guy that fixed mine at the independent shop told me that if a dealership technician thinks your swap is suspect (whether it be emissions related or otherwise), the dealership has the power to basically delete your vin number from the dmv all together. Like I said, I'm not sure if thats true, but I was happy to pay him the $95 for fixing my issue and I was on my way.

                    All buttoned up and back together:
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                    Last edited by mdmike; 06-03-2020, 12:45 PM.


                      How's it drive? I gotta say, the Hemi is A LOT of fun to have under the hood. The 1st thing people usually ask is "How fast is it"? The thing is, the Hemi doesn't really have that "hot rod" kind of feel to the power. The motor just seems to have power everywhere in the power band. It doesn't really like to spin up to high rpm's, it just likes to lug around effortlessly. With 4:56 gears and 35's, I turn 2k rpm's right at 70 miles per hour. It comes out of the hole hard, and will smoke the tires if you want, but its more fun to just drive around at 1/4 throttle and ease into it. The exhaust is quiet enough that I've caught a few people by surprise when they think they're going to jump a light and get in front of the "big slow Jeep".

                      My gas mileage stayed exactly the same between the 4.0 and the Hemi at 14 mpg around town.


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                        About 3000 miles into the swap, I suffered the first casualty. The \"new\" replacement Taurus fan that I bought from Rock Auto died. The motor just quit and wouldn\'t run on high or low. I reworked my fan mount, threw a cheap leftover Flexalite fan on it I got for free from my buddy at Appalachian Offroad, and life was good for a while. \n\nA couple thousand miles later, I developed a coolant leak in the radiator. The radiator started to split where the tanks met the core on the driver\'s side. I went back on my ebay account and found I still had 1 more month on my warranty through Superior. Sweet, right?! That is until I got in contact with them. I explained to the guy what was happening and where it was leaking, and that I had basically built my entire cooling system around this radiator. Their answer was for me to take the radiator out, box it up, and send it back to them for \"inspection\". IF they found themselves at fault, they would replace the radiator. When I offered to buy a second radiator and have them refund me once they inspected it, I was basically told to kick rocks. The guy on the phone said that \"they\'ve sold hundreds of these radiators this year, not one has failed\" and \"I know how Jeep guys are, you zip tie a fan to the radiator fins, go out 4 wheeling, and tear the radiator all up\".\n\nFantastic customer service \n\nSo, at this point I needed to get the Jeep back together asap. I figured, if I\'m gonna get fawked on a radiator in the future, its going to be a cheap one so I bought this one from Amazon:\n\nSince this radiator didn\'t have the bung in it for my temperature sender for my fan, I bought this little guy and put it in the upper radiator hose where I had it coupled together:\n\nI also upgraded my freebie fan to a new Flex a lite bolt-in 13\" fan meant for the Jeep application. \n\nAt this point, the cooling system has been treating me well and runs right where it should temp wise.


                          How much customization was needed for the HVAC, and did you keep AC?


                            Originally posted by Eman Resu View Post
                            How much customization was needed for the HVAC, and did you keep AC?
                            The heater core lines from the Grand Cherokee worked nearly perfect. The one that goes to the rear of the intake had to be cut and sleeved, but the bends were perfect once it was shortened up.

                            I do not have AC yet. I kept all of the lines and components from both Jeeps in hopes of just having to get lines made. We'll see how that goes!


                              So, what good is a mall cruising Hemi powered LJ without a rockin' stereo system?

                              I wanted to keep everything hidden and still retain the cargo space of the longer wheelbase. A few years ago there was a guy that was kind enough to put up a cut sheet of his custom designed under seat subwoofer enclosure. Unfortunately, he passed away a couple years back, and his website is no longer available.

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                              All buttoned up with the seat foam trimmed up and the cover reinstalled

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