NP231 Swap

[Cory]

I'm swapping out one NP231 for anther NP231 in my 95 YJ.

The old one has a SYE and 2-low kit. The new one has SYE, 2-low, and 4 to 1 kit. The only differences (besides the 4 to 1 case) is a harness that connects near the top. The old harness point on the case has 4 tubes coming out.


The new harness point has just one post sticking up.


What is the difference? I'm guessing that maybe the old harness controls the vacumn lines that go to my front axle and engage the 2-piece passenger side shaft? Is that right? If so, can I replace the 2 piece shaft with a TJ shaft and not worry about the vacumn lines (if they are vacumn lines)? If they are vacumn lines and I replace the shaft, do I need to hook anything to that new post?

The harness points look like they are part of the case, but is there a way to swap them out for each other? Anything else I need to know? Thanks for any help.

 

[I Lean]

Correct, the 4-port one is the vacuum switch to control the front axle crap. The single-stud one is just an electrical connection, I believe. (like for the 4WD indicator light or whatever)

 

[Cory]

Correct, the 4-port one is the vacuum switch to control the front axle crap. The single-stud one is just an electrical connection, I believe. (like for the 4WD indicator light or whatever)

So if I get a solid shaft and block off plate would I be good to go? Just leave the vacumn lines unplugged and hook nothing to the electrical connection? Do the vacumn lines run anything else?

 

[I Lean]

Yep, should be good to go as you say. I'll double-check, but I don't think anything else is controlled by that vacuum switch.

 

[bryson]

On the front axle swap, you would have to figure out some type of seal... your old setup sealed on the outer shaft, and there is no machined surface in the housing for a seal in the standard location with the one-piece shaft.

The vacuum switch controlled the front axle disco, and your 4wd indicator... so if you don't care if the dash light works, you don't need it hooked up. Just make sure you plug all the vacuum lines.

 

[Cory]

The vacuum switch controlled the front axle disco, and your 4wd indicator... so if you don't care if the dash light works, you don't need it hooked up. Just make sure you plug all the vacuum lines.

Any ideas on how to plug the vacumn lines? I guess I would need to plug them both on the transfer case side and on the axle side.

Also on the transfer case there are 4 lines, but on the axle there are only two lines. Anyone know what the other 2 lines are for? The dash 4x4 indicator?

The light is not a big deal, but it would be nice if it worked. Do you think there would be an easy way to use the new electrical plug to run a signal to the light?

 

[Cory]

Does anyone have any experience "plugging" the vacumn lines? What did you use?

 

[bryson]

Any ideas on how to plug the vacumn lines? I guess I would need to plug them both on the transfer case side and on the axle side.

Also on the transfer case there are 4 lines, but on the axle there are only two lines. Anyone know what the other 2 lines are for? The dash 4x4 indicator?

The light is not a big deal, but it would be nice if it worked. Do you think there would be an easy way to use the new electrical plug to run a signal to the light?

Vacuum lines only need to be plugged off at the source on the engine. the ports on the axle and t-case don't matter if you're not using the disconnect anymore.

one of the extra 2 lines is the vacuum supply, and the other is for the indicator light. I think the switch that the indicator vacuum line goes to is on the pass. side firewall, and you could extend the wiring on that, and run it to the new t-case indicator switch.....I think.

Your indicator switch may be on the front axle disconnect too... but not sure.

 

[bryson]

Does anyone have any experience "plugging" the vacumn lines? What did you use?

Just go to AutoZone or something and buy a pack of assorted vacuum plugs ($1.99 maybe?) and stick one on the fitting. That's it.

 

[Cory]

Turns out that this was a much more simple problem than I thought. I found out that the vacumn line piece was not part of the case but a section that can be screwed off. I just had so much grease and dirt around the base of it that it looked like it was cast into the housing. I fixed the problem by swapping from one case to the other.

Thanks for all the info on the vacumn lines. I'll still need the info when I go to a one piece shaft. I just won't have to do it right now.