NP231 converting to NP242

[alpinetiburon04]

So it snows really badly outside; a few feet or so, I'd want the full-time option, or the Select trac? But it's an incredibly difficult swap to do, at least for someone like me who knows absolutely nothing about SUVs.

 

[falcon556]

So it snows really badly outside; a few feet or so, I'd want the full-time option, or the Select trac? But it's an incredibly difficult swap to do, at least for someone like me who knows absolutely nothing about SUVs.

Selec-Trac is the 4X4 system that uses a 242J transfer case that has both full time and part time options. The positions are:
2H 4HPT(Amber) 4HFT(Green) N 4LPT(Amber)
Command trac is the system that uses a 231J that only gives you PT.
The positions are 2H 4HPT(Amber) N 4LPT(Amber)
If it snows really badly a few feet or so, you can use anything you think is right.
You can use PT on everything that is not asphalt or like asphalt. PT needs the ground to "give" to allow some slipping to prevent drivetrain binding. Snow, ice, gravel, dirt, grass etc. you can use PT.
You can use FT on anything, anytime.
It is not a very difficult swap, get a friend who can do it and help him.

 

[falcon556]

Just finished replacing the 231J in my 99 XJ with a 242 I bought from a forum member.
The TC came with the switch wiring, shift gate and bezel.
Except for a couple of scratches on my arms, everything went very well.
A test drive confirmed good operation, shifting and light operation.
As of now all my Jeeps have Selec-Trac.
Two things left, replacing the decalls on the sun visors to match the new TCs and selling the 231s so I can recover part of the cost.
The only thing that I regret as I look back, is that I didn't swap them a long time ago, which was not really possible because I didn't know what it takes to get it done.
Many thanks to the forum members for all the information, couldn't have done it without you.

 

[Hayden]

How did the wireing go? did you just tap into the blackw/white wire at the back of the firewall? Was the bulb allready there or did you have to install it? Everything else a perfect direct replacement?


Thanks
Hayden

 

[falcon556]

How did the wireing go? did you just tap into the blackw/white wire at the back of the firewall? Was the bulb allready there or did you have to install it? Everything else a perfect direct replacement?

Thanks
Hayden

I first checked the connector on the right side at the back of the firewall.
On a 99 it is connector C107. There was a Bk/Wh wire on the top half in cavity 13 and nothing on the bottom half of the connector.
To check, I used a wire gounded on one end and attached to a pin on the other. I pierced the wire and a green word "Full time" lit up on the panel.
My son said that he didn't need it, so I left it disconnected. I soldered the original Black and the BL/Rd to the new connector on the TC and the amber works like it used to. Lights up on PT positions.
No warning needed in FT. I understand that the WJs (like my 01)don't have a green light.
Besides soldering the 2 wires, everything else was a perfect direct replacement.
One last thing, while doing this, I cleaned and greased the output splines.
It prevents DS binding.

 

[falcon556]

I have a 98 XJ that I am wanting to take original NP231 out of and swap in the NP 242 so that I can have the full time option. I know for the most part it is a direct bolt in. My question is for anyone who has done it, what does it take the change the wireing so the "full time" light will come on? I am trying to make this look as factory as possiable. I know there is a location for the full time light but im not sure if there is actually a bulb in it or not. I would also assume the switch on the T-case uses a different plug for the indicator wires. If anyone has any insight on this I would appericiate any help.

Thanks
Hayden

I can tell you how to get the green light.
If you don't have a connector for the 242 get one and connect the existing Bk/Rd and Bk wires to the same color on the new connector.
The new connector has an additional Bk/Wt wire and possibly a fourth wire.
Disregard the fourth wire. Get a piece of 18 gauge wire (Preferably Bk/Wt) connect one end to the switch Bk/Wt and the other splice it to the Bk/Wt wire of the upper half of connector C107. This wire will provide a ground through the switch for the green light.
If you have any doubts which is connector C107, look in the engine compartment, right side, behind the oil dipstick. It takes 14 wires, the one you want is #13 BK/WT, second from the corner, #14 is DG/BK and #12 depending on year is either empty or BR/LG .
Good luck.
PS If you have any doubts, pierce the BK/WT wire you found with a ground wire and one of two things will happen, green light if you are right, something burnt if you are wrong

 

[Hayden]

I finally got my swap completed. One thing I noticed that has not been mentioned is the tab that bolts to the side of the t-case for the shift rod needs to be changed out with one for an NP242. The np242 one is indexed the same but it is a little shorter. Other than that everything else went very smooth, I actually had a pin that would go into the factory connector and ran the new wire for the full time light in the harness so its about as factory as it could be.




Hayden

 

[falcon556]

I finally got my swap completed. One thing I noticed that has not been mentioned is the tab that bolts to the side of the t-case for the shift rod needs to be changed out with one for an NP242. The np242 one is indexed the same but it is a little shorter. Other than that everything else went very smooth, I actually had a pin that would go into the factory connector and ran the new wire for the full time light in the harness so its about as factory as it could be.

Hayden

Congrats, glad everything worked well.
I never mentioned that flat link because normally it comes with the TC.
Just to make sure we are on the same page, you used the short flat link with the 242, right?
Normally there is nothing to change, you take down the 231 with its long link and put up the 242 with its short link.

 

[Hayden]

Thats right, I used the short plate with the 242. When I pull cases I usually just take the nut off so that I don't have to pry the rods out of the bushings, they become loose if they get taken in out too much.


Hayden

 

[PapaPump]

The guy who has been running a modified (has 2wd) 242AMG since sometime in '03, Mike R

I was curious about 242AMG cases, but wanted 2wd, so I just got a jeep box. How difficult was it to make the AMG box have a 2wd selection? Also, do those cases have a LSD when in full-time mode? I know Hummers have Torsen diffs front and rear, but also had read once that they hade center LSDs as well.

This thread keeps popping up to remind me that i have a fairly fresh 242 in the garage begging to be installed. The only thing that has kept it out is the too-long driveshaft (it has a SYE, but was in a jeep with 5.5" of lift, mine is stock height)

i don't ever plan on going beyond 3" of lift, but i am weary of shortening the driveshaft for stock height, only to have it not fit at 3" of lift later on. what is a guy to do?

 

[casm]

This is a no-brainer decision.

If you have need of the full-time mode and don't intend to push more than approximately 1400lb/ft of reduced torque through the drivetrain (at which point the transfer case will be the least of your worries), then go with the 242.

If neither the power output nor a pavement-capable AWD mode suits you, run the 231 and enjoy being able to put more or less 2000 reduced lb/ft of torque through the case.

A stock XJ puts out (at most) 235lb/ft of torque. Multiplying that by 2.72 (the low ratio in both the 242 and 231 cases), we end up with 639.2lb/ft as the absolute maximum either case will be expected to tolerate in stock form. This means that no stock Cherokee can put out more than about 33% to 42% of the potential torque that it's capable of handling at the transfer case.

If you intend to get really wild with your drivetrain, you've probably already planned on replacing or beefing it up. If you haven't, you should.

In any event, put a skidplate under them as any weight on them will cause the cases to fail - rapidly, and when you most need them not to.

 

[Root Moose]

I'm not sure where you are getting your numbers from.

You must multiple the engine torque by the transmission 1st gear ratio. That would be 2.8 for the AW4 (* 2.2 to compensate for the TC) OR whatever ratio the first gear in a AX15 is (3.8x:1?). That means the NV242J is just able to deal with the AW4 at 1450 lb-ft of torque. The 2.2 number is a fudge factor...I've heard 1.7 - 1.8 is more appropriate for the AW4. Whatever. Also, automatics are said to be "gentler" on drivetrains so maybe that is why Jeep used the "under rated" version of the NV242 for the XJ. Dunno, rampant speculation there.

Point being, I really think the NV242J in stock form is marginal for a machine that will be wheeled hard. The t-case out of a WJ or a AMG/Jeep hybrid may be a better solution and worth looking into.

I run a NV242J and wouldn't give it up for anything. If/when I ever break it due to wheeling I'll build a hybrid. I like the case well enough that I'm thinking about sticking one in my YJ. 15 years of Subarus will make you covet AWD I guess.

 

[JEEPZZ]

The t-case out of a WJ or a AMG/Jeep hybrid may be a better solution and worth looking into.

I too am a big fan of the AWD capability of the 242.
I know that the 242 was available in the ZJ & WJ with a 6cyl and then in 00 or 01 you could now get it behind a V8 for the first time. I just assumed it was the same 242 in the XJ and ZJ. What was the difference in the WJ case that would make it a better choice and was the WJ 6cyl 242 the same as the one they matched up with the V8?

 

[Root Moose]

My understanding is that the WJ/Durango case has the cooler of the AMG case.

Not certain if the planetary drive has any of the upgrades of the AMG case.

Also not certain if the WJ got only the HD or the J and HD version of the NV242 depending on engine. The give away as to which case would be the cooler lines coming out of it I would expect.

 

[MJR]

I was curious about 242AMG cases, but wanted 2wd, so I just got a jeep box. How difficult was it to make the AMG box have a 2wd selection? Also, do those cases have a LSD when in full-time mode? I know Hummers have Torsen diffs front and rear, but also had read once that they hade center LSDs as well.

Well using some parts from a Jeep 242. No the 242AMG does not have a LSD but open diff just like all 242's. Military HMMWV's I believe used a different t-case. Here's some descriptions and photos.


Forward differential gears. AMG on the left and Jeep on the right. Note the extra half teeth on the inside of the Jeep one.

AMG differential locking collar on the left and Jeep on the right.

Shift fork sectors. Jeep on the left and AMG on the right.

Modified AMG rear shift fork on the left and stock Jeep one on the right. Modified/added a notch near the top for mode switch to indicate correctly for use in a Jeep.

Mike R

 

[MJR]

If you have need of the full-time mode and don't intend to push more than approximately 1400lb/ft of reduced torque through the drivetrain (at which point the transfer case will be the least of your worries), then go with the 242.

If neither the power output nor a pavement-capable AWD mode suits you, run the 231 and enjoy being able to put more or less 2000 reduced lb/ft of torque through the case.

A stock XJ puts out (at most) 235lb/ft of torque. Multiplying that by 2.72 (the low ratio in both the 242 and 231 cases), we end up with 639.2lb/ft as the absolute maximum either case will be expected to tolerate in stock form. This means that no stock Cherokee can put out more than about 33% to 42% of the potential torque that it's capable of handling at the transfer case.

First off in the "real" world either t-case has the same breaking point which is the smallest part of the shaft where the speedo gear rides and both have the same size 27 spline rear outputs. I have seen both break in this "same" spot under trail use.

With the 4.0L putting out 235ft/lb x (AW4) 2.804 first gear ratio x 1.9 torque converter multiplication = 1251.986 ft/lb although torque transfer is smooth compared to a stick shift.

Manual trans models AX-15 had a first gear ratio of 3.83 and NV3550 had a first gear ratio of 4.01.

My main reason for upgrading the 242 was I would like to run a Klune 4:1 underdrive box if front of the t-case so the torque figure would be bad for a standard 242.

I know that the 242 was available in the ZJ & WJ with a 6cyl and then in 00 or 01 you could now get it behind a V8 for the first time. I just assumed it was the same 242 in the XJ and ZJ. What was the difference in the WJ case that would make it a better choice and was the WJ 6cyl 242 the same as the one they matched up with the V8?

242's used in Dodge/Jeep up until 97 were pretty much the same. Then in 98 (used until 99) the Durango ones behind a V-8 were upgraded to a HD (carry the 242D tag). In 99 (used until 03) the Grand Cherokee models with V-8 came with the HD models carrying the 242J tag. Also the 242J used in the Liberty has at least the HD shaft (not sure about the other internals).

My understanding is that the WJ/Durango case has the cooler of the AMG case.

Not certain if the planetary drive has any of the upgrades of the AMG case.

Also not certain if the WJ got only the HD or the J and HD version of the NV242 depending on engine. The give away as to which case would be the cooler lines coming out of it I would expect.

No 242/231 Jeep or Dodge t-case I know of has ever used a cooler (though the flat spots exist in the later castings without drilling).



Mike R

 

[Hayden]

Now that we are on 242 mods.....Anyone ever seen or heard of a way to make a 242 have a 4:1 low range and or 2wd low range? I think I read somewhere about a beefier output shaft, whats the deal with that.

Hayden

 

[Showmemuny]

Has anyone tried the NP242 behind the Klune-V?
I was wondering about the torque on the input shaft of the NP242. I got one and after reading this tread I'm thinking of swapping it in my '88 Cherokee. I pulled A NP242 out of a '87 Cherokee, so it should swap OK. So the two transfers are pretty much the same internally right? except for the option of FT4wd.

 

[MJR]

Now that we are on 242 mods.....Anyone ever seen or heard of a way to make a 242 have a 4:1 low range and or 2wd low range? I think I read somewhere about a beefier output shaft, whats the deal with that.

Hayden

Yes was one company that did a 4:1 for a 242 and you have to send them your front case half for them to do it. I DO NOT recommend it because the low range gears are smaller/weaker. I do not know of anyone offering a shaft upgrade but if you have the time/money you could piece something together.


Mike R

 

[falcon556]

I actually had a pin that would go into the factory connector and ran the new wire for the full time light in the harness so its about as factory as it could be.
Hayden

Hayden, I see nothing wrong with the way you wired it and this is no criticism.
I write this for others that may have to decide on a course of action.
The following comes straight out of my '01 WJ owners manual, page175.
"There is no light for the 2WD, 4 FULL TIME, or N(Neutral) positions."
Basically they figured that a green light for a normal condition was unnecessary and IMHO a pain to have it ON all the time. It took them a while to come to the same conclusion I did when I had an '87 Selec-trac, a few years ago.
I recommend to anybody that doesn't mind if his XJ does not conform to the early factory specs to get rid of the green light.