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AW-4 Transmission Swap

As was mentioned at the beginning of this write-up, the AW-4 is an electronically controlled by a small TCU (computer) and as such, the swap entails having to deal with the electrical requirements of the transmission.  Some folks are uncomfortable around electrical projects and struggle with the prospect of mounting a pair of driving lights on their vehicle.  In all honesty, the electrical work for this swap is not all that daunting and if you can't do this part of it, I'm confident you can find someone that can assist.  Consulting your local 4x4 club should provide you with a body or two that can help with the wiring task.

Bob Bassett and Scott Kruize both did AW-4 swaps before I did and their efforts in documenting the wiring were very good.  I got to help Scott do his swap and while he did the research for the wiring harness, I got the task of soldering it together.  I remember reading through Scott's notes and while very complete, they were a little confusing (not written the way I prefer wiring pinouts).  I was also recently involved with some custom wiring on a Vortec V-8 swap into a TJ.  That documentation was VERY poorly done and all that worked on the swap agreed.  So....I promised myself that when I did this write-up, I would try to make a more user friendly (I hate that term but it applies here) wiring diagram.  In speaking with Troy, he prefers a straight forward wiring list rather than a schematic.  He said a "connect wire A to switch contact B" was easier to follow for him.  So I put together a wiring list that contains the same information that ScottK provided in his write-up.  It is my hope that you will find either Scott's documentation or mine helpful.  The important part is that you are comfortable following one of them so that your AW-4 project goes well.

Here is the wiring list for my swap.  The first page contains the black and gray connectors for the wiring to/from the transmission itself.  The second page contains the TCU connector.  Scott's AW-4 came from a 2000 XJ while mine came from a 2001 XJ.  In both cases, the wire colors on the three electrical connectors were the same.  Credit for the third page goes to Scott Bentley, another AW4 transplantee.  (is that a word?)  While we were discussing some of the details of this write-up online, it was suggested that a page covering the wire colors between the tranny and the black and gray plugs might be helpful.  So that is the source and reason for page three.

Pages four and five of my wiring list are optional.  I say optional because it is for making the wiring harness completely "plug 'n play". The 9 and 6 pin connectors are basically put in between the wires that connect the AW4 to the TJ. This means that the TJ will have a 9 pin and 6 pin connector soldered into its wiring harness too. The AW4 will have the matching 9 pin and 6 pin connectors soldered into its harness.  When these two connectors are plugged together, all of the AW4 signals and TJ signals will be "cross connected".  This is the place in ScottK's project where he used wire taps to connect the AW4 wiring into to the TJ.  You do NOT have to do these two additional connectors in order to get everything to work correctly.  I did them because I could and I wanted a little cleaner install under the hood.  The choice is yours.  I would suggest reading both ScottK's and this write-up and then make up your mind as to how you want to do yours.

NOTE:  On my wiring list, pages 1 and 2 assume that you will NOT be using the optional connectors listed on pages 4 and 5. 

The wiring list for pages 1 and 2 is pretty straight forward.  The connector/pin numbers on the left side of the list show the "FROM" location and the connector/pin numbers on the right side of the list shows the "TO" location.  Read across one row and you will connect a wire FROM there TO here.  Pretty easy, eah?  If you are mildly interested (and you should be) as to what it is you are connecting, the middle column provides a description/function of that wire.  Note that not all pins in all connectors are used (some are blank). 

The important thing to remember when doing electrical work is to take your time and do it correctly the FIRST time.  Having to go back a second or third time becomes a pain in the neck (or worse).  Double check yourself several times as you locate each wire on the connector and confirm it is the correct color you are going to be soldering.  Spending the extra time while constructing the wiring harness will save you a lot of time trying to diagnose a shifting issue later on.


This this will take several hours to do properly (in my opinion), so you might as well get yourself comfortable.  I grabbed a folding table (my wife doesn't let me solder on the dining room table.....any more), a patio chair, and a piece of scrap particle board (much harder to destroy with a hot soldering iron than the actual table top). 

A good soldering iron (or low wattage soldering gun) and a roll of rosin core solder is needed for good electrical connections (do NOT use acid core solder, like the kind used for plumbing projects!).  I picked up a new wire stripper from Radio Shack just for this occasion (about $15) and I am happy to report that it worked very well.  I wish I would have gotten it long ago!  I also picked up several 4' lengths of heat shrink tubing. I got tubing sizes in both 1/8" and 3/16" diameter.  It costs about $1.50 per length so budget yourself a few extra dollars for this part of the project. 

On major projects, I always try to add a little something to the tool box.  While I could have used the new wire strippers to satisfy this requirement, I've always wanted a heat gun.  I found one at Fry's Electronics (where I bought the 4' lengths of heat shrink) for $30.  It is a dual temp (500F and 1000F) model and I'll tell you now that it worked very well....my heat shrinking days of using a BIC lighter are long gone.

I had spent some time the previous day with a tape measure while under the hood of the TJ.  I decided that I needed about 5 feet of harness to go from the end of the black and gray tranny connectors to the TCU connector.  Since the TCU is not at all waterproof, I opted to mount it inside the vehicle.  This goes along with it being mounted inside the XJ as well.  I also prefer to have a little extra cabling rather than not enough, so my measurements take that into consideration as well.  My advice is for you to select the TCU mounting location and then use a tape measure to determine the cable length that works for your needs. 


With the necessary length now determined, I sat down with my brandy new wire strippers and stripped a couple dozen lengths of wire.  I adjusted the stripper to remove 1/2" of insulation.  It worked very nicely!  I find it easier to do a bunch of the same steps repeatedly, such as stripping the wire....saves all that time of putting down one tool and picking up the next, over and over and over.  OK....so I now have a good supply of wire.


They say that necessity is the mother of all inventions.  That being said, I quickly found out that I needed a third (and forth) hand to hold the wires in place while I soldered them together.  I stole two clothes pins from Donna's laundry room and grabbed a couple of 1 pound lead ingots from my reloading bench.  A couple of wraps of electrical tape (sorry, the duck tape was all packed away in the TJ's rear storage box) and my third and forth hands were ready to help.  The lead bar is heavy enough to keep things nice and steady (no sliding around).  A brick would have worked too but I'm not sure my old card table could have survived.


Be smart!  Don't forget to slide the heat shrink tubing over the wire BEFORE you make the connection (especially if you have a connector already attached to the other end of the wire).  Hey, I only did it ONCE during the entire soldering episode....not too bad in my opinion! 


After a couple of connections were soldered, I would fire up the heat gun and shrink the tubing.  That too worked very nicely.  I think I am going to enjoy electrical projects much more than I have in past years.  You can see the wire extensions being added to the gray connector in the above photo.


A group of wires successfully attached to one of the 8 pin connectors.  After I finished the first connector, I started taping the wires together once I had 3 or 4 wires completed.  It was starting to turn into a rats nest of twisted wires and that only leads to making mistakes and an overall messy work space.


Here is the harness after a couple of hours of work (not yet completed).  The two coils of wire will be finished later on this week when I get some more time.  They are the wires that will be going to the TJ's wiring harness.  The 9 pin Molex connectors I got at Radio Shack will be used for this section of the harness (pages 4 and 5 of the wiring list).  Once it is all completed, I'll wrap it completely in electrical tape and then slip a plastic wire loom over it to prevent any abrasion. 


More AW-4 Tranny Swap



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