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Hey folks. With the 97+ XJ conversion becoming increasingly popular, I thought I would try my hand at a write up on it. This will be to cover the bulk of the conversion. The things necessary to get your MJ assembled correctly and back on the road running. Before I start I'd like to give big thanks to Bo (shelbyluvv), Ryan (Rymanrph), and Brett (87Warrior) for helping me with this writeup. Without their trial and error, knowledge, and help a lot of us would be stuck scratching our heads.

 

Now, to begin. let's assume you have sufficient mechanical aptitude and are aware of what project will take. But if you run into anything don't hesitate to ask! Ideally you will be working with your truck and a donor XJ. Your truck will need to be stripped completely down. All the interior, carpet, dash, seats, trim, everything. Also the drivetrain needs to come out, as well as all accessories under the hood. You can leave some things like the steering box, brake prop valve, brake lines and reuse them if you so wish. It's entirely up to you. Wiring harnesses need to go too. The only harness to keep will be the one on the drivers side inside the truck that goes to the fuel tank and rear lighting. As for the donor, take your time during disassembly. I strongly suggest investing in a Sharpie, masking tape, and a box of gallon sized freezer bags for organization. Also, invest in a camera and use it way more than you think you need to. When pulling plugs on the wiring harnesses, mark the plug with masking tape and write on the tape what it plugs into. Some of the plugs (larger bulkhead connectors) you can even mark on the plug itself. A good example is the three plugs that go into the ECU under the hood. Same thing with vacuum hoses, etc. It will make reassembly a heck of a lot less painful. Before you start tearing into it, take lots of pictures of how everything is mounted, routed, plugged in, etc. Take pictures of how things fit, where they are mounted, how they are bolted in. Take photos along the way during disassembly, the more things you pull off the clearer look you will have at things. The more photos you have, the better. Remember, you can always delete them later.

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Now, the first thing is sheetmetal work inside the cab. Let's assume the floorpan is good and your truck does not need any repair work. This thread is covering just a conversion. There are other threads that cover repair and similar issues. The firewall between your MJ and your donor XJ are similar, but the holes in them for wiring, steering column, etc. are different sizes and/or in different locations. What we need to do is fill in or cover up all the holes you will not be using. Personally, I used scraps of floor pan as patches and welded them into place.

 

 

You can use any sheetmetal you'd like and any method to attach it. For instance, rivets work great for attaching your patches to your original firewall. Keep in mind, you can do this entire conversion without a welder.

 

 

The main thing is to alter the hole for the fuse box and the hole for the steering column. The original fuse panel hole is square and the hole we will need is oval. Also, the steering column hole is about an inch closer to the booster on a 97+.

 

 

For mine, I cut out the firewall from the XJ and cut it into pieces to use as patches. For the steering column, I cut the original hole a bit bigger then cut around the 97+ hole, making sure to include a couple holes for the booster bolts to properly orient it. The fuse block will no longer be used under the drivers side, instead it will be replaced with a wire loom coming in and an oval gasket in the same location as the original panel. I cut the firewall a little larger than the oval then used the section of 97+ firewall as a patch for it. The rest of holes for the clutch master cylinder, etc. are covered with whatever pieces of sheetmetal you'd like providing you are replacing a stick with an auto.

 

 

The loom, hood release, steering column, brake booster, throttle cable, and the hole for the original ecu should be the only ones you need on the drivers side. I left another hole for the 4ga power wire to my amplifier to pass through. There is also an oval shaped hole on the passenger side of the firewall that needs to be covered as well.

 

 

A hole near where the new TCU will mount will also be required for the auto shifter cable. The hole that the heater core/AC evaporator passes through is also slightly different in size. You can use extra foam padding on the HVAC box to seal up this hole. It wil be fine to leave this particular hole alone. Personally, I cut out a filler plate (just a squared ring of sheet metal to fill the gap) and welded it into place. And the last hole in the firewall we will need is a round hole just above the HVAC box close to the passenger side inner fender, up at the top. (It isnt drilled yet in this pic but this gives you an idea where it needs to be. Refer to the XJ for an exact location.)

 

 

This will be where another wire loom passes through. On the passenger side kick panel there is a hole for the antenna wire to pass through. This one is also in the wrong place as well as the wrong size to fit the 97+'s antenna wire grommet. It will need to be patched and another smaller one cut. I would suggest patching the original from the outside first, then mount the new fuse panel into place for an idea of where to orient the new one. On all the holes you covered up, you will want to seal them with seal sealer to keep the moisture and rust out. Be fairly liberal with the stuff and make sure its in all the nooks and crannies. I also suggest you use the seam sealer on the inside and outside of each patched hole.

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To take care of mounting the dash, we need new bolt holes for the lower dash mounts, as well as new tabs and holes for the upper dash mounts.

 

 

In Bretts (87Warrior) case, while he was looking at the 99XJ dash bracket system he noticed a dimple above the lower mounting point. After some measurements, he determined that this dimple in the 99 XJ bracket lined up almost perfectly with the factory MJ lower dash mount and thus drilled it out and mounted the dash. This is just another option you could explore when mounting the dash.

 

 

We Will also be cutting out a few braces from the doner and welding them to the trucks firewall. These will serve as 2 upper dash mounting points, as well as a mount for the aluminum steering subassembly on the drivers side. Keep in mind that in order to do this, you will need a spot weld driller to remove your original steering column mount/ ECU mount/ dash support as well as pulling the required braces from the XJ.

 

 

I measured the location for the lower dash mounts first and drilled my holes. Then used nutserts in those holes to have something to thread the bolts into.

 

 

Once I had the bolts threaded in some, I hung the dash onto them and pivoted it up into place to get a good idea of where the new bolt holes were going to be for the upper dash mounts. I used more scrap metal and cut some new tabs to weld into place along the bottom of the windshield frame, welding them to the original tabs.

 

 

 

Others have done it differently, but the way I did it worked for me. I have no rattles or squeaks in mine. For the brackets you cut out of the donors firewall, measure where they will be on your truck and weld them into place as well. The larger of the two on the drivers side, I used the booster Aluminum subrame and pedal assembly to orient it into place and it worked just fine. The smaller of the two is a little easier to locate. Once your lower and upper dash mount holes are drilled and donor bracketry is welded into place, The bulk of the fabrication/metalwork is done. Your dash should be mounted into place correctly. And don't forget about your VIN plate. I can't tell you how to do it, and don't know the laws in your state. However you do it, make sure it is in accordance with your local laws. The next bit of metal work is the front seat mounts for the 97+ seats. If you plan to use your original seats, then skip this part. The mounts we need are welded in the floor of the XJ. All we need to do is grind the welds down along the edge and drill out the spot welds. There are braces that will need to be removed from the floor of the MJ for these to fit properly. Once those are out of our way, The new mounts will need to be notched to clear the ribs that run the length of the floor over the frame rails. I notched mine to butt against the rib then welded it up to the rib as well as to the floor/trans tunnel/and rocker panel. Please, make sure your seat mounts are facing foward before you weld them.

 

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Now, to actually start moving things over. This is assuming youve stripped your MJ of all its front skin, core support, everything under the hood, and everything in the cab. The first thing i moved was the windshield washer bottle. It was the only thing under the hood that required some cutting on the truck to make work. We will need to cut a hole as well as a notch for the filler neck to pass through the inner fender. Once that is done you can mount the bottle. After that, it is just a matter of moving things over one at a time. Most things will need new hols drilled in the inner fenders to mount. The ECU, cruise control vacuum canister, relay panel, emmisions pump, etc. Once all your accessories are mounted, start installing the under hood wire harness. If you labeled everything, it will be painless to route and plug into everything.

 

 

When all that is moved over, start moving vacuum lines, brake lines(optional, I used the donors booster/MC/propvalve/front lines), fuel line, emissions lines, etc. I would also suggest removing the original wiper motor and replacing it with the donors wiper motor. It really isnt required, but I didn't want any more wire splices than necessary.(plugs are different on the wiper motor). When you get all acessories moved over but still havent moved the driveline, now would be a good time to move the HVAC box over. It will be much easier to mount it without the engine in the way. Another thing that isnt required is replacing the heater core and evaporator core. But hey, since you have the box out and easily accessible, it's good preventative maintenance to go ahead and do it. I had a leak in my evaporator core and had to replace it anyway, so I did both while I was in there. (how many times do you really want to pull the dash?) The mounting stud on the HVAC unit closest to the passenger side fender will not line up to the original hole, so a new hole is going to be required here as well.

 

 

When we hve that unit mounted, now we can drop the drivetrain into place. On a note, when disassembling everything from under the hood of the donor, the wire harness that goes to the motor/transmission/transfercase can be disconnected and isolated from the rest of the wiring, making it unecessary to unplug things like the fuel injectors, tps, map sensor, etc. This will make reassembly go quicker. Just remember to mark and label your plugs to avoid frustration. Anyway, On stabbing the drivetrain into place take a look at your motor mounts and transmission mounts. Depending on the shape they're in, you may need to replace them. I know my motor mounts were shot and I needed new ones.

 

 

For the rear driveshaft, you may get lucky and not need a new one, you may not, depending on what you pulled out and what you're replacing it with. The only way to be sure, is to measure and figure out what you're going to need in your particular case.

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Moving on to the interior. Something I strongly suggest is to add some insulation while you have everything out. The foil coated bubblewrap insulation works great on the roof, back of the cab, inside of the B pillars, etc.

 

 

 

For the floor, you can go as cheap as the roofing stuff, or as expensive as dynamat. It's up to you and your budget.

 

 

 

 

 

The rubbber/foam heatproofing material from the donor will need to go back onto your firewall as well. When you pull it from the XJ, youll notice the big round plastic plugs that hold it into place. Unscrew them to remove them. What I did was use a pair of channel locks and break of the little studs they were screwed onto. Then I carried them over to the truck and welded them up in various locations on my firewall. You may have some from the old proofing you can use.

 

 

 

 

 

 

Where you need more to hold it into place, weld them onto your firewall. Depending on how pretty you want to make it, you may want to do this step before moving things over. Then after they're in place, paint the firewall inside and out. Once you get it the way you like it, you can start with installing your steering sub assembly. the bolts that will hold it in place on the drivers kick panel will need holes. Drill them and install bolts and nuts to hold it into place.

 

 

To clarify what is what,

 

The green locations are the mounting holes for the '97+ steering column/brake pedal brace.

I gained access to the lower right hole via the hole were the door wires go through, utilizing a wire to hold the bolt and prevent it from falling. This bolt will be welded on the inside to prevent it from turning and falling between the cab body panels.

 

The yellow locations are the factory MJ parking brake mounts

The two mounts on the right are still being used while the third on the left has been relocated. I used a button head bolt through the relocated parking brake bracket to clear the locking mechanism, secured with a nut against the bracket, then through the lower left (green) XJ aluminum bracket and hole. You can see the 2nd nut on the button head bolt shared with the aluminum brace to hold the unit in place.

 

 

 

Depending on if you want to keep the emergency brake in the original place or move it between the seats will determine what kind of alterations you will need for the steering brace and the e-brake assembly. I chose to leave mine in the original location. It required some clearancing and grinding to both the aluminum brace as well as the mounting plate for the e-brake assembly.

 

 

If you want to put the brake handle between the seats like the XJ, the bottom part of the bracket will need to be removed and located behind the assembly in the cab. This is to maintain the proper tension on the e-brake cable.

 

 

 

When you are happy with it, install the brake pedal and its assembly and hook your pedal to the booster rod. The TCU from the XJ is mounted to the firewall roughly in the center. We will need to move it over as well. Once you locate where you want to install it, you can use rivets or self tapping screws to mount it into place.

 

 

After that, install the dash and bolt it up to all those pretty new holes you made for it. Next is the steering column. Drop it into place and bolt it up as well. be sure to use the XJs steering shaft as well. This should take care of everything mounted to the firewall inside the cab.

 

 

 

Now would be a good time to hang your doors from the XJ. Once you get them into place, you will notice the strikers are quite different. Pull your old round strikers out and ditch them. For the backing plates, I drilled out the 4 spot welds that hold them in. When you get them out, use some strap steel or something similarly thing to make a new backing plate.

 

 

Pull your stikers from your donor and lay them against your new backing plates to mark for new holes. The way I did it was using strap steel, i drilled out holes to mount the new strikers to, then welded nuts to the backside of them. Simple and effective. You can also use the backing plates from the XJ as well. After adjusting your new doors, locate where your new strikers will be and mark your jamb. Drill new holes for the strikers to mount to and bolt them into place. Its helpful to drill your holes a bit bigger than the mounting bolts to allow room for adjustment.

 

 

 

 

Next, we will move the seat belts from the XJ to the MJ. When you pull them, you will notice the flat steel mounts for them are way too long to fit in the truck. Cut the bottom bit of them off and drill a new hole to mount them and problem solved.

 

 

 

Honestly, the only real reason for the seat belts is to keep everything in the cab the same color. Don't forget the female ends of the belts as well. They are bolted to the seats. You can choose to leave them bolted to the seat or you can unbolt them, straighten them and mount them in the MJs seat belt locations.

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Next will be a fun/frustrating part. Wiring. Its actually simple enough. Pull the wiring from your donor and label/mark as needed. carry it over and put it in the truck. Pick a side of the cab, and work from front to back getting it into place. There are a few large bulkhead connectors under the drivers side dash on either side of the steering column. This is where I started. I ran the looms down each rocker panel and laid the cross body harness across the the back of the cab. The rear of the harness is where we will have some fun. There is wiring for the 3rd brake light, hatch lock, rear wiper, etc. Things we don't have on our trucks. You're more than welcome to get creative and use these extra wires for whatever you want, but if not, you can cut them out of the harness and seal the ends up to keep from shorting. For the tail lights. I can't tell you the exact colors of each as there are 7 years of MJs and 5 years of newer XJs. I tested each of my wires out for brake/backup light/left turn/right turn/running light. And used the existing harness to the rear to splice/solder a connection that would properly work. It is a bit of a headache, but with a little patience and determination it shouldn'e be a big problem. The drivers side of the donor harness also contains the plug for the fuel pump/sender. I left this intact and ran it out under the cab and to my tank as I was going to use the XJs pump assembly. For the part of the harness that runs down the trans tummel, run it as normal, and mount your airbag module in place under the console as it was in the XJ. On the passenger side. Mount the fuse panel to the kick panel and plug in the various plugs that go to it. Now is as good a time as any to make that hole for the radio antenna also. When you finish with the wiring and are happy with where everything is (don't forget your grounds), start putting your jute material/carpet padding, as well as your carpet back on the floor. It will need a little convincing around the areas where your new seat mounts are. After that, start installing your trim inside the cab. I used the A pillar trim from the XJ to match the dash better.

If you use them, you will need to use a dremel or similar to cut rectangle holes in the A pillars for the little clips to snap into. Once in place, you will notice they are way longer than needed, Measure them against the original A pillar trim as well as your B pillar trim and cut where needed and they will fit just fine. The rest is a matter of installing the interior back into place, Installing your console, then installing your seats. If you use the Kick panel trim from the XJ and you keep the e-brake pedal in the original location, you will have you make a cut on the top back corner of the trim to allow the pedal to move freely. You will also need to rerun the wire for the brake indication light on the dash from the harness under the console to the driverside location. I just spliced into the end of it and ran a piece of wire to the original e-brake and plugged it back in. Sorry, no pictures in this post as I feel as if the wiring and trim installation is simple enough to install.

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For the fuel tank, there are a few different routes you can take. The route I chose to use was to get a new tank without a slosh pan and an adapter ring for the XJs fuel pump and assembly to work.

 

 

I cut a hole in the top of the tank, and using the ring, dropped the XJs fuel pump in.

 

 

 

Bolted it up and plugged in the wire harness. This will require the tank to sit lower than where is was, necessitating longer J bolts and spacers. You can use the J bolts from the XJ tank, and use anything you feel will work as spacers to keep the pump regulator from contacting the underside of the bed. 3/4 inch should be all you need. There are also threads explaining how to use a TJ tank as well as a Dakota tank. You are more than welcome to use whatever means necessary to make yours work. To keep the check engine light off because of emissions, move the charcoal canister from under the XJ to under the MJ. I mounted mine under the bed and ran hoses from the two hard plastic lines that come from under the hood over to the canister. Also I ran a hose from the rollover valves on the fuel tank to the canister. It is my understanding that the canister on the earlier 2nd gen XJs is under the hood. If that is your case, mount it where it should be under the hood and run your tubing as needed.

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That should just about cover the basics of this swap. If you have any questions, feel free to post them up and they will be answered best as I can. Maybe one of the other guys that has completed this in part or whole will chime in with input as well. I hope this will help any of you guys in performing this conversion. Some useful project threads that go into more detail on certain aspects of this swap can be found here:

 

 

My Build viewtopic.php?f=7&t=29527

Ryans Build viewtopic.php?f=7&t=20535

Bo's Build viewtopic.php?f=7&t=11834

Brett's Build viewtopic.php?f=7&t=15166

 

And just to honor these awesome trucks, here are a few "finished product" pictures of them.

 

 

Brett's truck is still at the body shop getting finished up. We are patiently waiting on the final product of this immaculate restoration!

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Great write up.. I've done the swap over and you hit all the major things to remember and consider when doing the swap (and definitely some things i missed the first try on mine.. oops)

 

:bowdown:

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So I'm sort of confused about the gas tank situation. You got a new tank and cut a hole in the top, and used that ring so you could mount the xj pump through the hole. right? I'm assuming that you capped off the hole were the sender is normally supposed to go? What does the slosh pan do?

 

Thanks comanche.gif

Chad

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So I'm sort of confused about the gas tank situation. You got a new tank and cut a hole in the top, and used that ring so you could mount the xj pump through the hole. right? I'm assuming that you capped off the hole were the sender is normally supposed to go? What does the slosh pan do?

 

Thanks comanche.gif

Chad

 

You are exactly right. I cut the tubes off the inside of the original pump assembly and plugged the 2 tubes. Then used that piece as a plug for the original hole. The reason for getting a tank without the sloshpan is to prevent interference with the fuel level sender float.

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Great post one of many questions is with the xj bucket seat brackets whats the go with the two rear mounting points as the xj floor is flat and mj has a step in it ??? :help:

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Great post one of many questions is with the xj bucket seat brackets whats the go with the two rear mounting points as the xj floor is flat and mj has a step in it ??? :help:

I'm not sure I understand you fully. What do you mean by the MJ floor has a step in it?

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The inner seat rails on MJ were bolted to the floor is lower than the outside rails mounting point. XJ floor is the same height all

the way across for the inner & outer mounting for the seat rail brackets. Or i may just have it wrong, on a side note have my pics on Photobucket and should get my post up running tonight

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Best I remember is if you use the 97+ XJ seats, the rear mounts don't come in contact with the frame rail stiffener. I personally drilled new holes in the floor where the rear mounts were, then welded 3/16 plate under the floor to reinforce the mounting point. After that I ran 1/2 inch bolts, washers, and lock nuts through the seat mount/floor/stiffening plate and called it a day. Its worked well for almost a year since I put my truck on the road. Hope that clears it up some for you or at least gives you a better idea of it.

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Decent write up...

 

I plan on getting extremely detailed with my Next 97+ conversion Thread that I should be starting in the next few days...

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