NP231 WTF?

Will a NP231 from a 1992 XJ fit on a 1997 XJ?
I hear they have different length out putshafts on the AW4. Or widths or something.
Anyway my friend told me that if i didnt get a certain part installed internaly inside the 231 it would kill my AW4. They have the same bolt pattern why cant they mate?

between a aw4 and ax-15/ax-5 the input shaft on the tcase are differnt lengths so depending on if you have auto or not

depending on year and transmission the 231 may have a different length input gear. Usually the input gears can be swapped, and it's not that hard to do. If you can get the other case cheap ten I would buy it and see if you can use your input gear.
The determining factor on whether or not you can use your input gear is the cut of the teeth.
http://www.novak-adapt.com/knowledge/np231.htm
look near the bottom.

THANKU XJ BROTHERS!!!! SO ITS CALLED THE INPUT GEAR, AND THATS IT? ARE THE 1992 AND 1997 AW4 THE SAME? WHATS THE DIFFERENCE?
sorry about the caps.