How do you know it had the wrong T/case installed, and how do you know it was bad? I would imagine that this XJ has automatic...correct? On the console by the shift lever, what ranges are listed? Does it say: 2WD
4WD Lock
4WD High
Neutral
4WDlow lock
OR
2WD
4WD High
Neutral
4WD low
IF on the console by the shift lever, it is like the top example, the 242 was the correct t/case. IF it looks like the bottom example, thats for the 231. IF you switched them I would like to know how you did this. They are 2 different transfer cases. The NP231 is a part time case called command trac, with 3 operating ranges, and the NP242 is called selec trac, with 4 operating ranges. For all PRACTICLE purposes, you've just DOWNgraded your 4WD. The throw on the t/case lever will be different, and you may not have enough to engage fully, the 231. But if I was you....I'ld just replace what you had with one that works. Just so you know, the 242, is VEERRY finicky. Dirty fluid, or low fluid, can stop it from working. ...........WM