Power Wagon Registry - Locker Bypass Mod for 4lo, 4hi, and 2wd

For the '06 folks, until I get some new diagrams done, you need to use different wire colors than what's stated in this how-to as follows:

• YL/DB (05) is VT/YL (06)
• BR/WT (05) is WT/DG (06)

The secret to the sauce is basically overriding the transfer case position sensor. We're going to do this with a single-pole double throw (SPDT) switch. A single-pole double throw switch is one where you have two "on" positions. Sometimes they'll also have a third position ("off") such that it's on-off-on. We need this type of switch so that in one "on" position, we have the wiring as it was in stock form and in the other "on" position, we're bypassing the transfer case sensor with a 208 - 213 Ω resistor so that the computer thinks we're in 4-lo.

The transfer case sensor is actually pretty cool. It has different resistances based on the position of the transfer case lever.

• 2H - 1172 - 1175 Ω
• 4H - 677 - 691 Ω
• Neutral - 406 - 415 Ω
• 4L - 208 - 213 Ω

Surprisingly, all this mod entails is bypassing this sensor through another connection which has between 208 and 213 Ω of resistance. Based on this resistance, the computer believes it's in 4lo. There's nothing else to it. This means you get all the above new capabilities with the throw of a single switch. How cool is that!

If you haven't already gotten the 2005 FSM, please take a look on the left menu and download it now. You won't really need it because I've already given you a diagram, but it might be helpful to see the big picture on page 21-1296 of the 2005 FSM and 8W-31-19 of the 2006 FSM.

Here are the tools you'll need:

• Wire cutters
• Wire strippers
• 2' - 3' of three separate strands (i.e. 3 separate wires) of 16 - 18 AWG wire
• Waterproof crimp connectors. I used butt type crimps because it was all I had at the time
• Crimper
• Electrical tape
• 5/16" socket (for trans lever cowl)
• 10mm socket (for trans lever plate)
• SPDT switch (any 12v with two "on" positions should work. I picked up a 12v 10A one from Autozone that was a three position on-off-on because that was all they had)
• 210 Ω resistor (red-brown-brown-gold) I ended up using a 220 Ω (red-red-brown-gold) because it's all I had on hand. It works fine but it is outside of the 208 - 213 Ω range specified in the FSM. The gold band on the resistor represents a 5% tolerance.

This mod took me about four hours, but it shouldn't take you more than probably two. It took me this long because I had to find the wires I needed (I'm not familiar with wiring diagrams for vehicles and where those wires end up running physically), having to run out to buy the switch I needed, and because I was being totally anal about quadruple checking that everything I was doing was the right thing to do. I also wasted about 45 mins trying to disconnect the plug from the transfer case sensor. While I was 95% certain I had the right wires, I couldn't be 100% sure because they were almost at full arms length away and trying to determine whether the wire really was yellow with a dark blue stripe, or it was yellow with a black stripe. At any rate, I gave up trying to disconnect it and went with my gut that was saying I did have the right wires. You won't have to worry about that, because you'll have pics I took showing you exactly which plug and wires you'll be messing with.

90% of this mod requires you to be under your Power Wagon, so be prepared to be uncomfortable. I will tell you that you're going to be in an awkward position on your back giving yourself a neck cramp as you strain to be able to see what you're doing. You're also going to be working in a confined space to crimp connections to the transfer case sensor wiring. Just have patience, take your time, and you'll do fine.

Positioning of your switch isn't all that critical, but I decided to mount mine on the plastic cowl around the transfer case lever. I completely dismantled my transfer case lever cover so that I could run the wires through the exisiting hole that the transfer case lever already has. This made the wire runs short and very easy.

Let's get started with the pics then. Click on any pic to get a high resolution image with better detail.

I started by taking off the cowl around the transfer case lever. There are two clips one in the front and one in the back (respective to the front and back of the truck). The clip in the back is the one you want to work on and then lift the back up and slide it towards the seats to get the front clip unhooked. I actually did mine backwards so I had to rebend the front clip back into position when I reinstalled it. To be honest, I started here, because I thought that maybe the wiring I'd need to hack into would be here. It wasn't.

Since I didn't find the wiring I needed under the transfer case lever cowl, I started searching around on the transfer case under the Power Wagon. Jackpot. Here's a series of pics showing you what you're looking for. To start off with, find where your transfer case lever comes through under the truck and you'll be where these pics show you. Hint, you'll come in under the driver's side of the truck.

Yes, it's in a nasty spot, but the good news is that there are only two wires on that plug, and we're going to be working on both of them. Imagine if that was a whole nest of wires like the Final Drive Control Module (pg 21-1296 of the 2005 FSM).

Next I wired up the switch according to the diagram and ran the wires down through the transfer case lever hole. Now it's time to start cutting and splicing. Yes, this is the PITA part because it's in a confined space and at arms reach. What I did was to pull the sensor wires out of the plastic wire conduit and tear off the electrical tape to give myself a good chunk of wire to work with. Here, I've cut the YL/DB wire and put a butt connector on.

In this next pic, I've connected the sensor side of the YL/DB wire to a Yellow wire running to the "on" side of my switch that doesn't have the resistor. I connected the other end of the YL/BL wire which goes to the Final Drive Control Module to the White wire which is connected to the center pin of my SPDT switch.

I didn't have a wire / vampire tap handy, so I did it old school and trimmed some insulation off the BR/WT wire to connect my Green wire which goes to the SPDT switch "on" side that has the 220 Ω resistor.

I soldered the BR/WT and Green wire connection I made, then electrical taped everything up.

Next I stuffed as much of the wiring back into the plastic wiring conduit and pulled up all the slack into the cab of the truck.

Inside the cab, I started bolting the plate holding the transfer case lever to the floor (four bolts with a 15mm socket) back into place. I was really careful on the corner where I had the wiring come out to not tighten it down too much. If you're really enterprising, you could drill a hole through the plate (it's plastic) but there was a nice spongy gasket on the underside which seemed sufficient to seal around my wires.

I drilled a hole in the top front of my transfer case cowl to hold the switch. I decided to put it there because it was out of the way. I don't really like the switch, but it was the best Autozone had to offer at the time. I'll find a much nicer switch and change it out someday.

I tucked all the excess slack under the drivers side carpet.

Here it is all buttoned up again.

So here's the part you've all been waiting for. The previous two pictures were taken after I'd gone out for a test drive to make sure everything was working, so that's why the transfer case lever cowl is off in these pics and I hadn't mounted the switch in the cowl yet.

I better explain what you're going to see. Remember, we're tricking the computer into thinking the transfer case lever is in 4-lo by bypassing the sensor. So, when you flip the switch, the computer lights up the 4wd indicator on the dash. This is kind of nice because you have a reminder that you put the switch into the override position. To override the sensor, you flip the switch from normal "on" to the bypass "on". If you used a three position SPDT switch, the center postion "off" on the switch doesn't do anything, so you should skip over it. I wouldn't suggest leaving it in the off position because I noticed that switching from bypass to "off" still left the 4wd indicator on, meaning the computer still thinks you're in 4-lo.

Make sure you click on the pictures to bring up the high resolution ones so you can make out the indicator lights.

Here's the sway bar disconnected in 2WD

Rear lockers in 2WD

Rear and front lockers in 4-hi. I must have forgotten to take a pic of just rear lockers in 4-hi, but I did test it and it worked.

Well, that's it. Enjoy the mod and safe wheeling my friends.

DISCLAIMER: While I believe that this is a sound mod that will not cause any damage to your truck when used properly, I am not liable for any damages, real or percieved, to your PowerWagon, yourself, your occupants, or anyone else for that matter. If you don't have the necessary skills to perform this mod, then please have someone who does do it.

Thanks to YellowSally on DodgeForum for getting me pointed in the right direction.