AW4 swap into YJ - JeepForum.com
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post #1 of 2 Old 12-11-2017, 10:08 AM Thread Starter
Themsah
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AW4 swap into YJ

So I currently have a YJ 4.2l with a BA 10/5 manual tranny. I want to swap to a 4 speed OD. I have looked at all of the options and it seems for the money, the AW4 would be my best bet. (I would ultimately want to go with a 700r4 Gm but the conversion is going to cost too much) I have done a bit of research but cannot seem to find solid answers to many of my questions. I am sure they may have been answered on here a million times. Unfortunately the search option on this forum isn't the best. So maybe you guys can help get me pointed in the right direction.

So the first questions I have are about actual fit and connection of the unit. I assume I have the answers correct here but just want to check. If I understand correctly the AW4 should bolt to my engine without an issue, as long as it is an AW4 and not a A340 out of a Toyota. Are all the bell housings the same bolt pattern? Is there a difference in a 4cyl and a 6cyl bolt pattern? Not even sure this unit came in the 4cyl. Then in the back I am certain that my NP231 should bolt up, but I do understand there are 2 possible output shaft spline counts (21 and 23). This all should be pretty simple.

My next concern is the electronics. Now my YJ has a carbureted 4.2l and basically no computer controlling it. I understand that the aw4 is an electronic unit, but can run with a stand alone TCU. Or I have seen some guys basically wire a series of switches to make it shift manually. Does anyone have any experience with this, or maybe point me to some decent websites that might help? I am not sure of the connections to my YJ.

Finally is there a certain year or model unit I should be looking for are they all pretty much the same? I can find any info open if they change through the years they were in service.

Please keep in mind that I have weighed all of my options and I am 99% sure this is the unit I want to swap to. I would not like this thread to turn into the "Well you should just use blank unit instead of the AW4". I am particular about the fact that I want a 4 speed OD, and although I would love to have a GM model because they are bullet proof. I am not looking to pay a ton of money for adapter kits. I have considered the 42rh but ruled it out because the AW4 has a much better reputation for being durable. I understand the AW4 can be prone to overheating issues which is easily solved with a large trans cooler. So unless you have some information that contradicts the above statements, I don't think I will be changing my mind on the AW4.

Thanks in advance for your help.

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post #2 of 2 Old 12-15-2017, 09:32 AM
bgredjeep
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I can help with this. I swapped from a t18 to an AW4 in my crawler recently.

First, the AW4 will bolt to your 4.2. I installed one from a 96 XJ into my 87 YJ. I used an XJ flex plate, torque converter, and starter. Everything bolted right in. I would recommend a 91+ model trans for the 23 spline output shaft. I'm not sure if your current 231 behind the BA10 is a 21 or 23 spline, but if you are going to the trouble of the swap, I recommend the 23 spline and swap to a 23spline case if needed.

Second, the trans does use a TCU from the factory. This ties into the original engine harness on a Cherokee. There are diagrams out there explaining what you need to wire in the TCU for automatic shifting, but on a carb'd motor, I'm not sure you will be able. I understand it uses a speed sensor, CPS, and TPS, none of which you will have on a carb'd engine. I do have a Howell EFI on mine, but I didn't attempt to make my AW4 shift automatically.

If you aren't concerned about manually switching the gears on the AW4, check out http://www.radesignsproducts.com/. They offer several options for shifting an AW4. They have controllers available for as low as $110 to control the shifting solenoids for manual selection of 1-4. The cheaper options are used in conjunction with the factory XJ shifter (for P-R-N-D selection). You put the shifter in Drive, then use the secondary control lever to switch your gears 1-4. For my Jeep, I went with the Winters shifter they offer with the control switches integrated so I don't have to mess with multiple shifters. It was a bit more expensive, but much easier to mount, and a cleaner install than if I used their baja controller. I literally connected 2 wires to trans for the solenoids, and a power wire to the shifter. No other wiring was required.

With just a standard XJ shifter, I believe the manual valve in the trans will allow you to hit 1st, 3rd, and 4th gear with no electonics, but I wouldn't recommend driving that way.

Here's a thread with some general AW4 info. http://www.naxja.org/forum/showthread.php?t=1053970 There are also a few threads in the YJ section about members who have done, or are doing a similar swap.
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