there are yield torque specs and shock load ratings for axle shafts published somewhere. The more splines you have, the less deep they are cut making the axle cross section thicker. many axles snap at the end of the splines, not in the middle, for instance. I don't have a good link right now. the dana 44 ring gear diameter is 8.5" (about 216mm). the jeep one is exactly the same, but the titan diff now has an extra heavy double spider gear arrangement and a diff cover that holds more oil due to towing failures. the nissan version has a higher spline count than the standard classic 30 spline count on dana 44 axleshafts. So, in summary, the bearings and dimensional measurements are the same, but the nissan one has been ruggedized with 32 spline axles and the titan special diff arrangement. also, as I mentioned b4, the X/ titan get a full size truck axle tube thickness and brake flange whereas the jeep ones are dana 30 sized axle tubes pressed onto a dana 44 pumpkin. narrower and lighter duty (the same inner axles dia - but 30 spl, but the outer tubes are lighter duty).

so the axles aren't snapping on titans, but it was more of a heat treating problem with the diff gear set internals and that was adressed for 2006 it would seem. Now the 6 cyl fontys and X's don't weigh as much and don't tow as much so you don't hear anything rampant about 6 cyl D44 axle failures. An updated titan axle might make a kick ass upgrade for a 200mm base x axle assumming the abs is compatible. even then, X axles should fit in the titan housing unless the width is more on the titan. the d44 is a good X axle, but sucks for the titan. They ought to bring back the japanese one, but I know that they won't because it costs $50 more. the good thing is every napa in the country has axle seals and bearings for dana axles for cheap.