What are your goals?
With a custom converter plate transmission selection is endless. If you have obd2 emissions where you live it will need to stay compliant or get an exemption.

 

I think most people decide against 4BT swaps into XJ's because its impractical due to the engine's size and weight. It has been done, but I feel like its more to say you put a 4BT in an XJ rather than actually benefit from it. There are better choices for diesels to swap in.

 

http://www.cumminshub.com/4bt.html

782lbs wet. Yea it's kinda heavy.

 

It's big. It's heavy. But you can make it work, assuming you or your shop is good at fabrication. There are tons of adapters out there to any mainstream transmission you want to use. The 700R4 automatic and NV4500 manual are probably your easiest choices. You will get a lot of low end torque but the fuel mileage improvements probably won't offset the cost of the install for a very long time.

One alternative to look into is the Cummins repower program. https://cumminsengines.com/repower.aspx

It's a 2.8 liter 4 cylinder that's smaller and lighter than the 4BT. The ISF platform it's based on is sold internationally so it has a lot of history and is a pretty solid design. They added emissions compatibility for vehicles up to 1999 (pre-OBD II). It will fit under the XJ hood a lot easier. And at just over 500 pounds, it won't require suspension upgrades in the front. It puts out 267 ft-lbs of torque so it'll do reasonably well in an XJ. It's relatively new in this market but you can get bellhousings and adapters to mate it to Jeep transmissions like the AX-15 and AW4. However, I don't know of anyone selling a transmission controller that will work with the AW4 yet. You can probably use the factory TCM but you need to adjust the shift points, and then you need to have something convert the CAN bus output to the signals the TCM needs. You'll still need to fabricate engine mounts, figure out an intercooler setup, probably run dual electric fans, run an exhaust, replace the gas pedal with the electronic one that comes with the engine kit, and so forth. But if I was going to do a diesel XJ, this is the engine I would choose.

 

Rad designs makes a controller for the aw4. However if I was doing that swap I would put an NV4500 5 speed in.

 

Looking at their website, it looks like all of their stuff is to convert to manual control of the transmission. While useful, it kind of defeats the purpose of having an automatic.

 

It's still an automatic only difference is the rad shifter makes it so the aw4 can be shifted by the driver without working through the jeeps computer.
yes you have to move the gear selector but it still drives like an auto.
the aw4 with a solid torque converter is supposed to do well. I actually have one that I'm debating putting in place of my 5speed that's lost the 4th gear synchros.

 

why don't you give greg at overland diesel conversions a call. he makes adapters for many engine/trans configurations.
he is a wealth of knowledge when it comes to jeep swaps.

https://www.overlanddiesel.com/

https://www.facebook.com/OverlandDiesel/