What makes the NP 231J from a ZJ so special?

[Ted_Z]

So I finally got my hands on a NP 231 that came installed in a ZJ from the factory. I thought I'd share my findings as to what makes this version of the 231 different from XJ/TJ versions.

First difference, the ZJ 231 comes with a different position sensor. Pictured below, on the left the sensor from a 242 or 249, center the sensor from a ZJ 231, right the sensor from a XJ 231. The 4 pin ZJ sensors will indicate all modes. The 2 pin XJ sensor just tells you if 4wd is engaged. The ZJ sensors (242/249 and 231) are the same internally, but the 231 has a shorter thread. You can use a spacer to make a 242/249 sensor into the 231 version. But this wont neseccarialy work (see below).


Second, the ZJ 231 comes with a different mode selector cam. I found this really hard to believe until I had one in my hands. Pictured below, on the left is a mode selector cam from a XJ 231 (late model), on the right is a mode selector cam ZJ 231. As you can see the "bumps" on which the sensor pin follows are different. If you take a ZJ sensor and put it in a XJ 231 it will jam and you can't get into 2wd.


If you look at the following tracing you can see that it might be possible to modify a XJ cam into a ZJ cam (blue ink is the ZJ cam). That said I don't know that it would be worth it. The only thing that the ZJ version buys you is that you'll know you're in neutral. You can make the XJ sensor work with the ZJ wiring (but when you're in neutral the VIC will say 2wd).



To wire the XJ sensor to ZJ harness:
On the ZJ side, twist the black wire and the green wire with the orange tracer together. Connect these to one wire from the XJ sensor.
Connect the other wire from the XJ sensor to the black wire with the red tracer on the ZJ side.
Tape off the gray wire with the orange tracer on the ZJ side.

[zrtwooo]

Thank you for the information. Now what if I'm putting an unknown 231 into my 93 zj. I haven't looked at the aforementioned parts but if it's all together do I need to worry about checking the sensor? I pulled a 242 out of it so i'm sure something needs to be wired differently, right?
Thank you

[PassRunnerZJ]

Interesting, I just ran into this with the 231 SYE transfer case my brother built for me. He was more concerned with getting the same length front output shaft and didn't think that Jeep would do a different selector cam and sensor. I just looked at the thread length and figured the indicator pin would float and move OK, but I just locked it in 2 high like you said. I put the XJ sensor in and it stated working again and I really don't need the display to tell me i am in 4wd so I am going to just leave the old sensor plug in and seal the ZJ's harness end and then use the display area to mount a CB and/or some power plugs.

Thanks for detailing this especially with the selector cams. This will save others time in the future.

[GreenMachine]

out of boredom tonight... ill add that you can grind down the pin and round it off a bit like the factory tip, to the point where it will shift through the gears fine and it should show up on your display as normal. At least this is the case when i installed the 2 low kit. I dont think tera knows or cares about this issue with the zj case, but it threw me for a loop till i got my grinder out. just dont go too far, little at a time.

[exric]

Your made my day with this write up.
IS the ZJ VICs different too. Do you use the red and or black connector behind the VIC?
Please show and or post the part numbers.
Where we might buy them would cool too.
Thanks again