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Renix 1989 np231 Upgrade?


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I have an 89 MJ 4.0 with auto trans and np231 transfer case.  Now the engine, transmission and transfer case all work like new but, I use this truck as a daily driver which worries me.  In Michigan we tend to get a lot of snow during the winter months.  This sometimes leaves the roads snowy/icy in spots and dry in other spots.  But this is the exact type of surface when I need the four wheel drive.   I'm afraid that I'll burn up the 231 if I drive on this type of surface if there are to many dry patches.  With that said, should I consider switching over to the np242?  So that I don't have to worry about the part time aspect of the transfer case and can use the full time four wheel drive option instead?  If so, I'm confused on how easy it will be to switch over.  I know I can get a transfer case and shifter assembly from the JY but my understanding is that it won't be an easy "plug-n-play" swap because of the front axle.  Is this correct?  Any input will be appreciated. 

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As long as you're not going around corners in 4x4 you should be good. When I still had my 231 I left it in 2wd for the most part in winter, just using 4x4 to help with stopping and starting. Decent winter-rated tires really put you further ahead there. 

That said, having upgraded to it I really enjoy the 242 tcase. You gain almost all the traction of part-time without any of the handling drawbacks. I do still go back to 2wd on the highway if I can, as there's a noticeable effect on mpg in full-time. But in snow or on gravel that full-time 4x4 is awesome.

I suspect you could pop the vacuum bit out of your 231 and stick it in place of the electric switch on your 242, at least that's the way it looked from the outside, but I didn't really investigate too far with that as I had already upgraded to a one-piece shaft before the 242 came around.

As others have said, permanently lock in the CAD or swap to a one piece or whatever, and you'll be good regardless. Do as I did, make the vacuum lines go away (unless you want them..?) and plug in the wires to make the lights work if you so desire. I think with the Renix gauge cluster you have the advantage of the full-time light being present, or at least a wired socket, unlike on the HO where they didn't bother printing that part of the circuit board. 

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As already commented, just lock the front axle in the connected position and forget it. Jeep eliminated the front axle disconnect after a few years anyway, and nobody missed it.

 

By all means, get the 242 transfer case. The 2000 XJ my late wife drove has a 242. When the first snow of the winter came, I used to just put it in full-time 4WD and leave it there for the duration of the winter. There are no handling issues as a result. My wife never had a problem with it.

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On 2/11/2018 at 10:54 AM, 90comancheman said:

Guys,  Thank you all for your input.  Based on your info my plan will be to move forward with a 242 and do the CAD lock in.  

 

If youget your 242 from a junkyard, be sure you also get the shift gate and bezel from the donor vehicle. The shift gate for the 242 is different from that gate for the 231.

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On ‎2‎/‎11‎/‎2018 at 1:27 AM, Eagle said:

As already commented, just lock the front axle in the connected position and forget it. Jeep eliminated the front axle disconnect after a few years anyway, and nobody missed it.

 

 

 

But, it's coming BACK for the new model year....so it must be great again!!!  or better than it was before!!!

 

(smell that?  that's sarcasm......)

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9 minutes ago, mjeff87 said:

 

But, it's coming BACK for the new model year....so it must be great again!!!  or better than it was before!!!

 

(smell that?  that's sarcasm......)

 

My bet is it will show up for a couple years, be problematic, and then they'll figure out some other way to save .03 mpg and eliminate it again.

 

But that's just speculation.

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It's electric this time around so hopefully more reliable. But I guess time will tell on that.

 

Nearly all manufacturers include a front axle disconnect of some kind, it's generally how the "automatic" 4x4 settings work, stick the tcase in 4x and then just lock and unlock the front disconnect as needed for extra traction, giving you the supposed ability to run 4x4 without a centre diff on snowing roads without an issue. My parents split their transfer case using it, fortunately it was noticed during a trip to the dealer for some other issues before the completely dry tcase locked up on them in the middle of nowhere. Can't stand using "4A" in my Jimmy, don't really notice it much on good traction but spin the tires a bit more than you'd care to leaving a stop sign and it slams the front wheels into motion so hard I'm convinced something will break... But I guess you make money when you sell new transfer cases. 

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On 2/10/2018 at 9:08 PM, 90comancheman said:

  In Michigan we tend to get a lot of snow during the winter months.  This sometimes leaves the roads snowy/icy in spots and dry in other spots.  But this is the exact type of surface when I need the four wheel drive.   I'm afraid that I'll burn up the 231 if I drive on this type of surface if there are to many dry patches. 

 

You are aware that you can shift on the fly between 2WD and 4WD high, right? I've driven hundreds of miles on roads just as you describe. Just shift into 4WD for the snowy or icy parts, and shift back to 2WD for the dry parts. That's what that handle next to the gear shift is for.

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