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NP 231 difference


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This guy is selling both.  He doesn't know what year they are from but says they both from a wrangler.  The one without the shaft is the same as the one on my jeep.   I got a couple questions.

1. Why does one have a shaft stocking out the back and one does not?

2.  Both transfer cases have build dates of the year 95, will I be able to bolt either of them up to my ax-15 with no problems.  I read something about the planetary gears not matching up, or did i read to much into it.  

 

Just trying to get the jeep up and running by this weekend as I have a wheeling trip planned.

jeep shaft no.jpg

jeep shaft.jpg

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Hmm.

 

The top one should work.  It will bolt to your AX-15, ASSUMING it is a 23 spline input.  I believe if it's from a 4cyl application it will be a 21 spline.  Count it to make sure before purchase.

 

I think the bottom one is bastardized, and is a later style output shaft put into the earlier style tailhousing.  If this was done for a good reason, or out of ignorance, I'm not sure.  You can see the red/orange RTV on it, that's not factory, it has been apart.  It looks like it's bolted to an AX-15 right now, so it would bolt to yours based on that, but your driveshaft will not work with whatever is going on with the output shaft/tailhouing.

 

The difference in the planetaries has to do with if you need to swap the input gear.  94/95 was the change IIRC (by build date), and you can not put an early input in a late planetary set, and vice versa.  If that top tcase is a 21 spline input, you would not be able to put the 23 spline input gear out of your early tcase in it.  Do NOT be fooled by people telling you that you can, always look at the gears side by side if you are doing it and make sure the teeth are the same angle and profile.  You can physically jam it in there and bolt it up but it will blow itself apart, however there is people out there that have heard you can do it, likely from people that assembled a tcase that way and have not yet run it to find out it won't work.

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The top one without the altered tail shaft is the one I’d try, if it’s 23 spline. It looks normal, although I don’t know why it has vacuum switches. Thought jeep did away with those 92-93.

 

The one with the altered tail shaft looks Frankensteined, I don’t get why is has a front housing with a switch and a rear housing with a vacuum switch near the speedometer gear. I have a couple np231 for the renix era and early HO none of them look like that. It may be ok functionally, I do know the later late 90s np231 changed their tail shafts to look like that but unless you have time to experiment I’d try the top np231 again if it’s 23 spline.

 

 

Sent from my iPhone using Tapatalk Pro

 

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Those round silver tags will have numbers stamped into them....they will give you info on the type....231/242/207....ect......as well as an original assembled date code.....

 

And if you are not aware already if from an early wrangler (YJ) the bolt pattern will be slightly different...... The clocking will be off....(this can be over come) 

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Top t-case has a build date of 9/12/95. So according to Novak as long as the case has a short input shaft and 23 spline it will bolt up. Then I know I might have to take the hammer to the under side to get it to fit which I’m fine with.  

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2 hours ago, Green Mesa XJ said:

If the AX15 you’re using is out of a XJ or MJ the clicking is fine. Jeep used the transmission tale housing to clock the transfer cases.
 

 

This.  It's the transmissions that are drilled differently.  If you look at an AX-15 you can see where there is extra meat on the tail/adapter housing for it to be drilled the other way.

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8 hours ago, Green Mesa XJ said:

The top one without the altered tail shaft is the one I’d try, if it’s 23 spline. It looks normal, although I don’t know why it has vacuum switches. Thought jeep did away with those 92-93.

 

 

 

Wranglers still used vacuum switches until 1996 so this must be a YJ case.  It doesn’t have a true neutral in it

 

so if your MJ still use the vacuum system then you can use that, however if yours don’t, don’t bother buying it. 

 

 

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Just now, kook911 said:

Thought all the vacuum port did was light up the dash?  So the port actually does something more then that?

 

It applies vacuum to the 'motor' on the CAD actuator.  And yeah, to a vacuum switch to turn on the 4wd indicator light.

 

You can just leave it unplugged if you don't have CAD.

 

No idea about the comment that it doesn't have a true neutral, AFAIK all 231 cases use the same shift cam and have a neutral position, but I could be wrong since it isn't something I've ever needed.

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either. i usually grab my 6 point snappy or my 12 point craftsman chrome socket and physically put it into the input shaft. if it fits its 23 spline. I work at a jeep specific salvage yard and we have some real dummies that work in out shipping department that have no idea about parts and i showed them this trick so they would stop sending out the wrong tcases for orders.

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44 minutes ago, strictlyxjs said:

protip: a 13/16 chrome socket will fit into a 23 spline input shaft but not a 21. i always take one with me to save time in figuring out that bs.

 

Why not just have the person count the spline?  Wouldn’t that save you the trip?

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they have their own sockets at the shipping station they can use to check lol....show them one time and then tell them to check everytime before boxing them up. we ship out 4-5 np231s everyday in all sorts of configurations. sometimes i travel to other junkyards to buy their tcases off the shelf. thats when i bring my 13/16 socket with me to check them. when you are dealing with buying 20-25 cases at a time its easier to check them quickly rather than counting each one before loading into the truck.

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29 minutes ago, kook911 said:

 

Why not just have the person count the spline?  Wouldn’t that save you the trip?

 

Many CL or Facebook sellers can't be trusted to count a number higher than 3.  If that.

 

That said, I'd count them, always.  Paint pen the first spline and count from there.  Often they were marked from the factory.

 

The OD of a socket is not an established value.  I could measure all the ones in my toolbox to make a point, but I'll spare everyone that.

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