Doing It The Hard Way - JL Steering Box and a Front Stretch

I ordered an XJ PDC from DeadJeep to hopefully salvage some connector terminals from in order to expand my existing PDC. I also got a connector for the JK fan, so far I've just been using spade connectors on the terminals. I'm still not sure which route I'll go for fan control, whether I'll use a standalone controller or just use thermal switches.

Looks like I might be needing a new radiator cap. Is Stant the go-to recommendation?
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I might not bother with this, but I'm thinking of swapping my driver and passenger seat around so that I can mount them farther apart. I've got Corbeau seats that aren't designed for a TJ and the recline lever runs into the roll bar. Because of that, the seat isn't quite centered on the steering wheel. It looks like I can move it at least an inch or two before it touches the door.
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I'll have to make sure the seat belt receiver doesn't get in the way of the lever though.

FYI, Liberties of the same vintage use the same PDC as well. I went to the pick and pull, looking for a cherokee, but ended up salvaging a PDC from a liberty for 15 bucks or something.
Try to get a Mopar radiator cap and thermostat when at all possible.
The quality on Stant nowadays is highly suspect. MotoRad pretty much rules both those markets now and they are lacking…

Good info. Looking at my radiator cap, it does look similar to what MotoRad sells, so maybe there's correlation there. I'm sure my thermostat is just some parts store junk I put in about 6 years ago. Mopar stuff is getting harder to find for these Jeeps, but looks like Summit has what I need. Thinking of just going ahead and doing a thermocure flush while I've got the system opened up for a new thermostat.
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Got the XJ PDC in, along with the JK fan connector pigtail. The pigtail I ordered was actually for a '10-15 mustang, way cheaper on eBay than the ones for a JK, but it is the same connector.
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After a very tedious time, it's fully disassembled:
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The plastics are extremely brittle and I ended up breaking a number of the plastic tabs. Glad I got some practice in before messing with the TJ PDC.

Here's a before shot of mine, just for reference:
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As you can see here, I've got 5 empty maxi fuse slots. I wanted to make them all available for future use, so needed to insert some connectors.
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After carefully prying the bus bar out the back, I popped in the missing connectors down the middle two rows. The outside rows are added in with the wiring, which I'll just add when needed.
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Next, wanted to swap one of my 2 slot large relay inserts for a 4 slot small relay insert. I wasn't able to get it past the wiring, so I had to de-pin the last row as well.
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You will need to file off this tab from the PDC frame to fit in the different relay configuration
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Next, since the starter relay was already de-pinned from the end, I wanted to convert it to a small relay like you see on later TJs and also relocate it. I'm not sure what the current requirements are for the circuit, just assuming it will be fine since it is on later models.

The connectors are different, so I needed to snip the end off the factory harness and add in one of the harvested ones from the XJ. I (carefully) ripped the connector off the wire.
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Then I soldered it onto the factory wire. I don't generally like to solder automotive wires, but none of the harvested wires were close enough in wire size to just use a butt connector. I had heat shrink on there for strain relief, but I had to cut it back off for it to fit in the fuse box.
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Got the relay moved to up near the mini fuses. Zip tie so the wires share any strain. The other wires in the background with the blue tape are for the rear window defrost, but I don't use that so I'll just insulate the contacts and tuck those wires away somewhere.
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As careful as I was, I still broke two plastic tabs when inserting the connectors to the housing, so had to load them up with some hot glue. Seemed to be adequate to get the relay plugged in though. I used butt connectors for the smaller trigger wires.

Got the box reassembled enough to test that the Jeep still starts, and it did!
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The two big relay spots will be used for low/high speed fan relays, and that leaves me with 5 more slots for other things, like lights or air pumps.
Overall I think it will make it so my PDC does everything I will need it to do, but I can't say I'd recommend this to others. The plastics are just so brittle you're likely to screw something up, like those two contacts that are only held in by hot glue now.

That's definitely enough for today. Still trying to wrap my head around the best way to wire up the fan.
I applaud your spirit of adventure to modify the PDC! I love a good OEM looking install but this is way past my risk tolerance!
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Alright, I'm no electrician but I think I've got this figured out.
The fan is just High-Low-Off. Low just sends power through a resistor before the DC motor. No PWM or anything. This probably won't apply to more complicated fans.
The diagram I'm using for reference is from another forum, but I liked the functionality and simplicity. I did have to modify it slightly, so I'll try to make my own diagram of what I did and post it later on. I probably won't bother with the auto/off/on switch, but will definitely be adding an A/C switch somehow.
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Here's the mess I've got put together for testing.
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  • Switched +12v is supplied from the previously de-pinned rear defrost trigger wire (red/light green). It is fused at #11 behind the glove box and goes to 86 on both relays. This is on ACC power, so the fan can still run when the engine is off but key is on
  • The black relay is the ON/OFF trigger
  • The green relay is for speed control. Normal state sends power to LOW, triggering the relay diverts power to HIGH
  • The left rocker switch simulates the LOW temp trigger, which would be a thermal switch in the coolant loop, or trigger from some fan controller
  • The right rocker switch simulates the HIGH temp trigger, would be another thermal switch -or- A/C on (I think normally done through a refrigerant pressure switch/trinary switch)
  • The input side of both rocker switches are connected so that when HIGH is triggered, it also triggers the ON/OFF relay so the circuit will complete. This is so the A/C can trigger the fan even if the coolant temp is below the low threshold.
  • A diode was added (seen on alligator clips) to prevent the ON trigger from also completing the HIGH circuit
Everything seems to be working as expected in this configuration, so I guess it's time to get it more finalized. I don't really know anything about diodes, so I'll need to make sure the one I used is appropriate. It's just one I had. Wiring is tricky!
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Realized I never posted a final pic of my fan wiring, at least how it is for now.
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Having the relay control on a switched power source has been great, I don't have to pop the hood open and connect or disconnect an alligator clip from the battery every time I park or start a drive. It just turns the fan on when I put the key in. Wow!

As a side note, forget everything I said about adding a diode, Lingenfelter has a much better diagram to follow. Basically my power needs to go through the green relay first instead. I'll revise my wiring whenever I dive back into the fan control, but for now it seems to be working just fine.
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I'm going to add a coolant filter into the heater core loop. The filter housing has 2 extra ports that I will be able to use for temp sensors. That will be a whole project though, because next time I open up my cooling system I want to do a full thermocure flush, replace the thermostat, take a look at the pump, etc.

I went ahead and did fluid changes on my transmission and transfer case. I wish I could remember what fluid I used last time, because it didn't do well at all. I want to say it was valvoline syncromesh in the transmission, not sure about the transfer case. Both have less than 10k miles on the fill and had significant metal contamination. The transmission fluid was very thin when it came out, like 0w20 thin. I don't know if it broke down or what. My first gear synchro is basically shot so I was expecting to see brass, but not as much as I did.

Filled both up with Rotella T1 30w straight grade because I had it, we'll see how that does. Seems fine so far.

I've been getting more comfortable driving the Jeep over the past week. Took a fresh look at my alignment and had to center the axle a little, then re-center the steering wheel, probably because the springs are settling. I also had my toe way off. Measured at the edge of the rim, it was set to 3/16 toe OUT. Set it up to have 1/16 toe IN instead. Not sure how I botched that up so bad, but it is a lot less darty now.

I developed a heat issue with my power steering as well. I siphoned out what old fluid was in the reservoir and added ATF+4 to it, thoroughly bled any air, then went and drove on the highway for the first time, and pretty quickly had it sounding like a supercharger from 2k to 3k rpm. PS pump temp by the time I was able to check was 250°F.

Not knowing if it was from the ATF I added or just because it was my first highway drive, I decided to flush the system and put in fresh NAPA power steering fluid. I took the same drive with that, and no more whine, but the temp was the same. 250°F is too high, right? I obviously have the extra variable of a JL steering box complicating things, but I'm inclined to think it isn't related since the temps go up with RPM rather than steering effort.

Pump on its way out? Need to enlarge the restrictor valve orifice? Just throw a cooler on it?

On the plus side, the Jeep drives extremely well on the highway, definitely better than it ever has. Really liking the extra caster. About 200 miles into my gear break in now, itching to open up the cover and see how things look. Diff temps are still running about 165.
Alright, time for the 500 mile update!

I got the front diff drained and took the cover off to inspect it. There was definitely a lot of very fine metal particles in the oil, but I assume this is normal for a break in.

Here is the magnetic drain plug:
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Everything on there was extremely fine, like anti seize:
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Oil looks like it was getting a little frothy in there, some foamy oil left on everything 2-3 hours after I parked. Kinda weird but I don't know if that means anything.
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@hosejockey61 @Blackjack how are these wear patterns looking to you? Should I run a paint pattern?
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Seems like the pinion maybe could have gone a touch deeper but I don't think its worth changing it now. Remember I don't have a front driveshaft so this was 100% driven by the wheels, not through the pinion, so I don't even know if this constitutes a proper break-in...
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Here's a bit of a status report on how things are holding up after about a month of regular driving.

You can definitely tell where the black oxide steel is, it's all rusting up already. Polished links are looking pretty bad already too, I blame the sprinklers. Anything painted with the Steel-It however is looking great.
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Looks like I've got a slight rear main seal leak... it's not dripping on the ground so its not my problem yet. :)
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Got a random drop of oil on the back of my transfer case too but I can't tell where it came out of, there's no trail.
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Exhaust is holding up fine, searched for cracks at my welds but didn't find any.
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Exhaust is definitely going through heat cycles based on the color. The DIY hanger done off the transmission is working great so far!
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...however the one by the rear UCA is too close to the hot muffler and melted a bit.
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The weld on that tab also failed, so I'll need to address that.
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Overall though everything is working well. I still haven't had a professional alignment yet, I might try to work on at least getting it measured by a laser machine to see how I did. I also haven't noticed any vibrations from the wheel I knocked 2oz of weights off of.

My tires have not contacted my rear shocks or shock towers yet.

My power steering pump still whines a tiny bit if I do a lot of highway hot weather driving, but nowhere near as bad as it was before changing the fluid.

At ride height and on a reasonably level surface, my front passenger shock shaft shows exactly 6", the front driver shaft is showing 6 5/16" though (without me in it). That's probably as much as the springs will settle, so the springs are pretty accurately a 4" lift over stock on my vehicle and its weight. (I had designed the suspension around the assumption that the springs would be 16")

Rear driveshaft seems to be holding up fine so far at the fairly extreme angle it is at.

Fuel mileage is pretty bad, worse than I remember. Last fill up was under 12mpg. I doubt just the extra 1.5" of ride height is responsible, so might need to investigate that. Not really sure why that would be unless my alignment is way off, which I don't think it is.

Cooling has been completely fine with the JK fan just set to always run on low, gauge is always about 2 needle widths below the middle tick. I'm still going to get a controller and do a coolant flush, but not overheating on low during summer driving is encouraging.

I do kind of wish my shocks were a little bit softer, but the ride is definitely better with a full tank of gas and a full Costco load vs empty.

Still have some little jobs to do on it but I'm pretty shocked at how well things are working after how much I changed and how little I knew.