By far the BEST mod I've done to my XJ. Even better than the custom D44 front.
The AW4 is a VERY strong/reliable tranny. I was sooo happy to ditch my Peugot with its puky internal slave. I haven't touched the tranny since it went in.
I wired in a 2nd gear please swt and am very happy with it on and off road. Only place I can say that the manual was better is when doing a steep downhill descent the manual braked better. But with 5.13s in the diffs it won't be an issue. I'm currently running 4.10s and 36" tires, have 5.38s waiting to go in.
The auto is so nice for just crawling over things, the torque convertor justs lets crawl along nice and smooth, no fear of stalling.
If you are going to do it you pretty much need a complete donor vehicle. There are a lot of parts you'll need. Search my name and you'll find a thread I started and kept up while I was converting mine. Autos here are really cheap. I paid $650 for a complete '89 XJ with 90,000kms on rebuilt motor. Ran perfect but the body and rear wiring was toast. For comparision just a used AX15 and related pieces needed to convert my Peugot would have cost me $800.