On the 425-55 and the x475-95 models, aws was an option. On the x700 series, aws is a different model #.
X724 or x734 - aws gas
X729 or x739 - aws, awd gas
X744 or x754 - aws diesel
X749 - aws, awd diesel
JD did not build a all wheel drive, all wheel steer diesel (x759) when the new models came out a few years ago because they would of had to put a roll bar on it, due to weight.
Well actually the X series were 4 Wheel Steer where the 4xx series were all wheel steer.What say ye to that?