INTRODUCTION

You might be wondering what an AW4 is? The AW4 is a 4-speed automatic transmission made by Asian Warner. This transmission can be found in the 1987-2001 Jeep Cherokee XJ's with the 6-cyl engine. The AW4 is computer controlled by a separate computer called the TCU (transmission control unit). The 1987-1990 XJ's have a rear output spline count of 21 verses the 1991-2001 XJ's with a 23-spline output shaft. The 23-spline AW4 is compatible with the t-case in all the 6-cyl wranglers and even the Dana 300. Now, you might be wondering why I swapped an AW4 into my TJ? I swapped in the AW4 mainly because I prefer an automatic over a manual transmission especially offroad and in city traffic, which this Jeep sees a lot of.

The reason I choose the AW4 was for its overdrive, durability, compatibility, and cost. The stock 3-speed transmission that came in the TJ's (from 1997-2002) is a 3 speed that dates back to the early 1970's with minor modifications to make it compatible with today's fuel injection systems. It is known as the TF-999, TF-904, & now that it is in the TJ's, it is called the 32-RH. Also, I had the 3 speed auto in my CJ7 and drove plenty of 3 speed YJ's and TJ's to know that I did not prefer its shift patterns compared to the AW4's.

PARTS

Here are some quick pics of most of the parts required for the swap:


WIRING

With the parts collected it was time to look at the wiring. For the AW4 you need to wire the TCU into the TJ's PCM. The TCU requires signals from certain sensors around the engine, which dictate shift patterns (one of the main reasons the AW4 is such a good transmission). I'm not going to go into detail about all the wiring needed. I will say that it is involved but nothing that can't be accomplished by the capable, confident, and experienced wrencher. I soldered all of my connections and then wrapped them in heat shrink. These are some pics of the progress of the wiring harness. Humble beginnings:











Tapping into the TJ's harness.







Test fitting the unfinished harness into the TJ.



The completed Harness ready for install.



Installed harness. Looks like it belongs there! Also a picture of where I mounted the TCU. It is covered in heat wrap and mounted to a piece of aluminum stock to reduce the heat it will come in contact with from the firewall.






ADAPTING THE NP231 TO THE AW4

The AW4 has a transfer case bolt pattern that is different than a TJ's transmission. The difference is 10 degrees counterclockwise. The NP231 found in XJ's has one major difference than the ones found in a Wrangler. The TJ's NP231 uses a longer output shaft then the XJ's by about 13/16." To solve this issue, I choose to re-drill the bolt pattern 10 degrees clockwise in the tail housing of the AW4 and cut off any excess length on my NP231's out-put shaft.

I was able to use a clocking ring I had in the garage for a Dana 300 to guide my drilling. The AW4, NP231, and the Dana 300 all share the same mounting pattern. I used the clocking ring as a template to find the 10* I needed for adjustment and then drilled my new bolt pattern.

Cutting the input shaft. I got creative here. I wanted as precise cut as possible, but not having a machine shop for a garage I improvised. I measured off 13/16", marked this measurement with a sharpie and used a hose-clamp as my cutting template. I used a 4" angle grinder with a cut-off wheel and it turned out great! I was even able to put a bevel on the edge of the output shaft. Almost looks factory!

TRANSMISSION MOUNT

I used a piece of 3/8" flat steel and a modified stock transmission mount to install the transmission back into its stock location. There are two bolts I had to insert into the plate due to interference with the stock transmission mount. I used grade 8 hardware, tapped threads for the bolts and screwed them into the holes after coating the end of the threads with JB weld. Final product came out nicely.




















COOLING

An automatic transmission runs on ATF (automatic transmission fluid). This fluid needs to keep cool. This, from the factory, is run through a separate cooling case that is housed in a tank on the bottom of the radiator. Some XJ's even have an external cooler in front of the AC condenser. There are many ways to run a cooling system for your auto, this is how I did mine.

I used Russell adapters to do away with the factory "quick connects" so I could run rubber lines straight to my coolers.



From the Russell adapters I ran my cooler lines in some heat wrap I picked up at the local racing store. The "hot" line goes into the radiator first (I am running an all aluminum radiator in this TJ), then into an aftermarket B&M super-cooler mounted in front of the A/C condenser. You'll notice that I have my B&M transmission cooler turned to the side. The inlet is on the bottom and the outlet is at the top. This technique is to ensure there is no air in the cooler, and that it gets completely filled with transmission fluid to maximize its use.














I also added a transmission temperature gauge and mounted the gauge in the front of the TJ's center console.









REMOVING THE AX-15

Remove the transmission skid plate 1st. This makes it easier to get to the front drive shaft, rear drive shaft, and the transfer case.





The AX-15 shifter uses a spring loaded retaining ring that needs to be pushed down, then twisted counterclockwise. It is easier to remove from underneath the jeep, but pictures of what I am describing is better from above.








With the transmission removed go ahead and remove the flywheel, pilot bushing, and the pilot bushing spacer ring that sits inside the outer crankshaft hub all seen here. I do not have a procedure or pictures to illustrate the pilot bushing spacer ring removal. I drilled three holes into the ring, then used a punch and a BFH to crack the ring and remove it from its housing. If you forget to remove the pilot bushing spacer ring the AW4 WILL NOT be able to bolt to the engine. The ring must be removed before transmission installation. I included a picture pointing out the ring that needs to be removed using the process above.





Installed the new automatic flex-plate and spacer plate. Install the AW4 just as you removed the AX-15.



Connect the transmission's TV (Throttle Valve) or "kickdown" cable. This cable is connected to the throttle body and informs the transmission when and how far the accelerator pedal has been depressed.
 





INTERIOR

I was able to use a complete shifter assembly from a 2000 XJ. Everything bolts into the existing mount locations and holes.






The shifter bezel from a 1984-1996 will fit directly into the stock consoles shifter slot. You will want to get a bezel from an XJ as the TJ bezels do not have the correct gear indicator. Also, I don't know if all TJ's are wired this way, but my 1999 TJ had a bezel light bulb provision in its interior wiring harness. All I had to do was install a bulb and mount it into the shifter bezel.













Lastly, the master cylinder holes were covered up by a factory master cylinder block off plate. I unbolted the clutch pedal from underneath the dash. I just used the factory brake pedal for a manual transmission TJ. Fill the transmission with fluid and enjoy your new automatic!