Just to be clear again, I have the 3 5 5 0 Not a 3 5 0 0. I have an NV4500 in my 2500HD chevy. The PO put 90wt in it and 2nd always grinds now, other than that I have towed and worked it a lot and it takes a beating *step 1 putting syncromesh into it*.
In all the jeep forums I have read they say that the ax15 is maybe good for 10hp more than the NV3550. They have stated that both are good trans for a 4.0L jeep or a mildly built small block. I couldn't find an ax15 and I found the NV for about as much as a rebuild kit and it came out of a 39,000 mile jeep. So that is why I am doing it this way. I personally think the NV 4500 is quite a trans and hopefully the 3550 will be similar for this wrangler that is 1/3 the weight of my truck and less power too.