Actually the newer AX5's have been improved a bit internally, when I blew 3rd gear in my 98
I found a used AX5 out of a older YJ and some of the bearings would not swap over. Turned
out they had beefed up the bearing on the cluster gear slightly in newer models with a wider bearing
so if your swapping parts have a micrometer handy. So newer is better as long as it's not worn out!