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AW-4 Transmission Swap

Well, it finally got to be time to swap out the manual AX-15 transmission and install an automatic transmission.  Unlike some tranny swaps done by others, I did mine because I could, not because I had to.  My AX-15 is running strong with no signs of trouble.  I opted for the AW-4 automatic that is commonly found in the Jeep Cherokee.  This tranny has seen hard use by the local XJ owners and I haven't heard them complaining about it.  Although Scott Kruize sold his AW-4 equipped TJ, I know the current owner and it is still running strong.  I wanted a tranny with an overdrive so the three speed auto that was available in '98 TJs wasn't really in the running.  Besides all that, finding an AW-4 tranny would be much easier due to the plethora of automatic equipped XJs.  Many a soccer Mom's XJ has met with early retirement directly after a traffic accident. 

I am putting this first part of the write-up together prior to doing the swap.  There is plenty of stuff to document before the first bolt gets turned.  I've spoken to Bob, the current owners of Scott's TJ, and if his schedule allows, he plans to help me wrench on mine.  Bob is a good friend and we've managed to do some fun trails together over the past couple of years.  If he can plumb the AW-4 cooling lines as well as he drives, I'll have it made! 

A few other thinks to take care of while I am thinking of them....the thank you part.  A big thanks to Troy at Toys by Troy.  Troy was kind enough to lend me some lift time in his shop so I didn't have to lay on my back on my driveway.  While it is certainly possible to do it with all 4 tires on the ground (that is how Scott's was done), standing under the vehicle during a project like this does have its advantages.  He also arranged for a price on the tranny that I would not have normally gotten.  Troy, thank you very much for your assistance on this project. 

Another thank you goes to Nacho at AMC 4x4 Salvage.  He gathered together all of the pieces and parts and provided me with a very low mileage '01 AW-4 tranny.  He put up with my typical 101 questions and still kept smiling.  The real test of his Jeep prowess will be when the TJ bracket I ordered at the Jeep dealership arrives and his XJ shifter fits in it.  If that all goes inside my console without the need to break out the SawsAll, my hat goes off to you!  Thanks for making it all come together. 

With that out of the way, let's get down to business....first, I'll run through the parts I picked up.



Here is the main piece of the project, the AW-4 transmission.  It had a bunch of dust on it, but not a single drop of fluid on the external surface.  If I remember correctly, Nacho said it has less than 10K miles on it before the donor XJ was in an accident and totaled.  Nacho also said that '98 to '01 XJs were the desired years for the TJ swaps.  Thanks goes out to another Jeeper who did this swap.  He told me that after some research, he discovered that the pre-'98 XJ AW-4 only had a single pulse output on the speed sensor while the '98 - '01 had a 4 pulse output.  The 4 pulse version is needed to work properly....at least for the wiring method ScottK and I used. 

The AW-4 has evolved slightly over time, but it is pretty much the same tranny that was first made available in the Cherokee.  It has a small TCU (transmission computer unit) or tranny computer which provides electronic control for the transmission.  Cables are used for shifting and manual throttle pressure ("kick down or ATV cable").  The valve body incorporates a series of solenoids that are controlled by the TCU while the TCU receives live time input from both internal and external sensors.  4th gear is a .70:1 over drive and the transmission uses a lock-up torque converter. 



Until I get some seat time with the new tranny in place, I could think of no reason to swap out the stock torque converter for one with different specs.  Besides that, I'm still reading up on stall speeds and all that other stuff that manual tranny folks never thought about.  <grin>  You can see the torque converter in the above photo.  Those 4 mounting bolts transfer power from the engine into the transmission.



Here is an XJ shifter (on the left), the shift cable, and the shifter's indicator panel (P,R,N,D,3,1&2).  The shifter and shift cable came out of a '98 XJ, not that it matters much.  They are all pretty much the same from what I have seen.  The XJ indicator panel just happens to be the same size as the opening in the TJ's console, so it will pop right into position when the time comes.



In the above picture, the flex plate is in the upper left corner.  The flex plate for most automatic transmissions is simply a stamped-steel disc with a ring gear located at the outer edge for engagement with the starter's pinion gear.  In the above photo, the 6 bolts and ring (shown directly below the flex plate) fasten the flex plate to the engine's crank shaft hub.  Those 4 bolts on the torque converter match up with 4 of those holes in the flex plate.  The dust shield is shown on the right side of the photo.  It installs between the engine and the transmission.



There are two cable harnesses attached to the transmission.  They provide control of the shifting solenoids and also tell the TCU what position you have selected with the shifter.  In the above photo, you can see the two connectors (transmission side) on the ends of the cables.  They are both 8 pin connectors but are not the same design.  You will see references to them in the write-up as the "gray and black plugs". 


More AW-4 Tranny Swap



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