[JrMechanic]

I know it's long, but I'm fairly certain this is the most in depth write up with the most information out there, so bear with me.

I ask that if anything is unclear or I have some bad information in this thread, please let me know kindly and I will be sure to edit it

****I'm currently offering fully rebuilt and upgraded cases. Below is an example of what's available. This particular unit is a NP231 built as a direct replacement for a 1995 V8 ZJ with a 1.55" input shaft and Rugged Ridge HD SYE. PM me for details****





This thread covers two swaps:

The NP231 recipient is my 93 ZJ with the 4.0/42RE/249 with the medium length input shaft. My new 231 from a 94 ZJ had the same length input, meaning I did not have to open the case.

The NP242 recipient is my buddy's 93 ZJ with the 5.2/46RH/249 with the long input shaft. The 242 donor was from a 92 XJ with the short style input shaft, meaning it was required for me to swap input shafts.

Parts Required:

NP231 or NP242 from an XJ or ZJ.

NP231: Part time transfer case used commonly in XJ's, YJ's, TJ's, ZJ's, etc. It offers 2wd, 4 part time, and 4 low.
NP242: Full Time transfer case used in XJ's and ZJ's. 2wd, 4 part time, 4 full time, and 4 low. The 4 full time feature is unique from the NP249 as it does not use a vicious coupler (what goes bad in the 249), but instead a mechanism that operates similar to an open differential.

There are 3 different input shafts, .750", .840", and 1.55", as well as both 21 and 23 spline shafts. All ZJ transfer cases have a 23 spline input shaft, and all 92-01 XJ's have a 23 spline input shaft. 91 and older XJ's have the 21 spline input.

Here's a good visual for those of you unsure of the different input lengths. From the left, I have a 1.55" input from a 249, a .840" input from a 231, and finally a .750" input from a 242. They are all 23 spline shafts with the old style gear cut and they are all three interchangeable between each case.

A word of caution to those who attempt installing a .750" input in place of a .840" input: If you look closely at the center (.840") input, you'll see the upper most wear ring on the input. This is where the transmission output seal rides on the input shaft. As you can see, it's not very far from the edge of the shaft (approximately 3/10ths of an inch). If you attempt this swap, I recommend sealing the transmission and transfer case surfaces with Ultra Black or Gray RTV. I recommend this if your rig sees any deep mud or water anyways to keep sediment from ruining the transfer case and transmission seals.




Your best bet is to find a transfer case with the same input shaft. If not, you can swap input shafts, but be aware of the annulus gear cut change that occurred in mid 94.

It's best to go by the build date on the transfer case, not the year of the Jeep when determining the gear pitch. Rule of thumb is cases with a build date of pre 94.5 will have the old style gear cut, and cases with a build date of post 94.5 will have the new style gear cut.

The correct way to read the date is just how it looks. Month, day, year. So if your case says 8 15 92 1, That would be August 15th, 1992. Most manufacturers aren't this specific on the manufacturing date which would lead you to believe "1" would be January, 1992, however the last number is insignificant.

My personal experience is that a 249 with a build date of 7/94 still used the old style gear cut.

If you're swapping a 242, you can do what is referred to as a front case swap if you're in a bind with two different gear cuts (no pun intended.) The 242 and 249 both share the same front case half, meaning you use all the parts from the 242, with the exception of the 249 input, 249 planetary set, and 249 front case half.

Here's a general rule of thumb when determining your input shaft length. This is not always 100% accurate, so make sure you know what you have before buying a transfer case.

93-95 V8 ZJ's: 46RH transmission, 1.55" 23 spline input shaft
93-95 I6 ZJ's: Used both the .750" and .840" 23 spline input with the 42RE and AX15.
93 I6 ZJ's with the AW4: .750" 23 spline input
All 96-98 ZJ's: .840" 23 spline input

Drive shafts: While there are several different length drive shafts used though the years, the physical dimensions of the 231, 242, and 249 are very similar. The overall length of each case is within + or - 1/4" of each other, per slip yoke configuration. There are two different slip yoke styles used for the rear drive shaft: Internal and external slip yokes. They are easy to decipher from one another as, well, one has an internal shaft with a tail cone and the other has an external shaft with a dust boot. The external slip yoke is generally found in 96 or newer Jeeps while the internal slip yoke is found in older Jeeps. There is really no huge advantage to either style, however I like how the drive shaft splines are always submerged in ATF in the internal slip yoke case.

The biggest difference between the two is that the external slip yoke case is about 1.5" longer than an ISY case, meaning if you replace your ISY 249 with an ESY 242 for example, you will have to cut and balance your rear drive shaft or have the drive shaft from the donor Jeep on hand.


NP231/242 T case Linkage:

This may be optional, but I only used the linkage that connects the shifter assembly to the transfer case, it is about 2 inches shorter on the NP231. You should be able to adjust the shifter assembly enough to make due with the NP249 linkage, but I found that this made it a bit easier.

NP231 Shift Indicator Sensor:

The NP249 sensor WILL NOT work in the 231, as the threaded portion is about 3 times longer. I attempted to shim it to no avail. You can however use the 249 sensor in a 242 case.

New Seals:

Cheap insurance if you're doing a transfer case swap.

Here's the part numbers for National brand seals from Advance Auto Parts:

NP242/231 rear output seal: 4370N
NP242 front output seal: 3946
NP231 front output seal: 710046
NP242/231 input shaft seal: 3173 (single lip)
NP242/231 input shaft seal: 710928 (dual lip, VERY nice seal!)
46RH, 42RE, 44RE, and 46RE transmission output seal (also known as rear seal): 710058


Fluid: The new T case requires 1.5 quarts of fluid, so grab 2 quarts of any brand/type of ATF. You will need around 2 quarts of ATF +4 to top off the transmission when you are done, depending on how much you lose from the tail of the transmission.

OPTIONAL:

NP231/242 Shift Gate and Bezel

Tools Required:

-30mm socket
-14mm or 9/16" open end wrenches (a 9/16" ratchet wrench is GREAT!)
-Metric socket set with ratchets (8-18mm, deep wells may be needed)
-Assorted extensions
-Misc. Screwdrivers
-Channel locks and pliers
-Air tools (optional)
-Hammer

Required If Swapping Inputs

All of the aforementioned tools are required with the addition of a good set of lock ring pliers, large pipe wrench, 1 1/8" socket, a 1/2" drive breaker bar, and a foot/pounds torque wrench. You will also need a tube of Ultra Black RTV.


Swapping Inputs

*Skip if you do not need to swap inputs*

NP249 Disassembly:

Start by removing the front bearing retainer from the input shaft of the 249. 4 10mm bolts hold it on.

After scraping off the excess RTV, you will see two lock rings: One holding the input bearing in place, and the other holding the input shaft into the bearing. You only need to remove the smaller lock ring if you are not using the bearing from the 249 case.

Here's a fun part: You need to remove the front output yoke from the transfer case. To do this, I found it easiest to put the case on the concrete and support it with blocks. Then, place a large pipe wrench or cresent wrench on the yoke, and apply pressure to the retaining nut with a 1 1/8" socket and 1/2" drive breaker bar.

Of course if you have an impact, you can just run the nut out pretty easily. Mine didn't have enough umph to get the job done however.

Next, remove the 10 15mm bolts holding the case together, and the 1 12 point 10mm bolt.

If you look closely, there will be one indentation on each side of the case where you can stick a flat head screwdriver in to pry the case halves apart.

Once you have the case apart, throw the rear half to the side. You will not need anything from it with the exception of the speedometer sensor.

Turn your attention to the front half: The 249 has a simple shift mode fork that just pulls straight up out of the case after removing the shift detent spring using a 7/8" wrench. Now you can remove the input shaft and it's planetary gear set. It may take a little tapping on the input shaft to remove it.

You can either use the entire planetary set and input from the 249 (what I opted to do) or you can use the 249 input in the 242 planetary.

NP249 apart:



NP242/231 Disassembly

I recommend giving the donor a good bath before you open it up. The less grime falling into the case the better.

The 242/231 disassembles much like the 249. Remove the bearing retainer on the front of the case, remove the input shaft lock ring, remove the front output yoke, remove the 10 15mm bolts and the 1 12 point 10mm bolt, and finally pry the case apart.

The 242 looks much like the 249 inside. However, it has a larger, more complicated shift assembly due to the different gear positions.





The mode fork is two pieces in the 242 and 231: Mode fork and low range fork. Remove the mode shift sleeve from the top assembly as well as the plastic pads on the fork.

*231 may be slightly different, the following description is for a 242*

Start by pulling the shift rail (long rod holding the fork assemblies together) straight out of the case. To do this, you will need to remove the rubber plug from the outside of the case and get a left hand drill bit to remove the pin.

Remove the shift detent spring assembly from the bottom of the case using a 7/8" wrench

Then, remove the mode fork, followed by the low range fork.

Now you can remove the input and planetary set.

I wanted to avoid removing the roll pin from the shift rail, so I had to pry the pin holding the mode fork into the shift sector away from the shift sector and pull the mode fork up and out. It takes a little prying, but it works.


NP242/231 Re-assembly

I recommend bathing the front half of the case in solvent to get rid of any grime that's present, then cleaning it well with brake cleaner and compressed air. Be careful with the input bearing and front output bearing. Either remove them before cleaning the case, or be sure to clean them very well with brake cleaner and compressed air afterwards. You will also need to remove the old seals at this time.

After you have the front half of the case clean and dry, as well as the 249 input shaft and planetary set, drop the assembly into the case, with liberal amounts of ATF to lube the gears.

Flip the case over and install the lock ring to keep the assembly from falling out.

242 front case with 249 long input installed:



After installing the snap ring, replace the front bearing retainer using a thin bead of Ultra Black RTV. Be sure to align the oil gallery hole up with the indentation in the cover, and torque the bolts to 16 ft. lbs. Now is a good time to install the new input seal as well.

Flip the case over again and install the low range fork into the case with the fork hub facing down into the planetary set. Be sure to lube everything with some ATF.

Then install the mode fork with the mode sleeve facing upright.

Slide the shift rail through the fork assemblies until it fully engages into the provision in the case.



Clean the magnet and place it back into the provision in the case. I like to use a little grease to keep the magnet from falling out upon reassembly.

Moving onto the back section of the case, visually inspect all the components for any stress cracks or abnormal wear. Also inspect the chain for any stretching.

Remove the old RTV from the back section of the case. A thin wire brush works well here as it's easy to score the aluminum with anything else.

Clean the case, gears, and chain with brake clean and compressed air. Make sure the oil pump pickup is clean from any debris.



Set the two case halves on the bench. Place a thin bead of Ultra Black RTV around one of the mating surfaces.



Put some assembly lube on the intermediate shaft splines, as well as any other mating/bearing surfaces.

Push the two case halves together, aligning the shift rail as well as the mode sleeves and the intermediate shaft.

The case should "pop" together with little effort. Once it's together, spin the input shaft and cycle the case through all the gears. If all is well, install all of the case bolts (the two holes with dowel pins use the longer bolts as well as washers, this is IMPORTANT!)

Torque the case bolts to 30 ft. lbs.

Install the new rear output seal and the front output seal. Install the front output yoke and torque the retaining nut to 110 ft. lbs.

The case is ready to go into your Jeep.

Transfer Case Removal and Installation

Start by either driving your Jeep onto a set of ramps or jacking it up and placing jack stands under your Heep. Be sure to chock your wheels, and PLEASE, PLEASE don't rely on a jack to support the Jeep. You will need it later anyways.

Drain the old T case (this is where the 30mm socket comes in handy, and be sure to recycle your old fluid!)

Check again that your wheels are chocked, and put the transfer case in neutral. Remove the front and rear drive shafts using an 8mm socket or ratchet wrench.

Remove the shift linkage from the Tcase, along with the speed sensor and shift indicator connectors.

Remove the shift linkage from the transmission by placing a pry bar between the linkage and the mount.

Place your jack under the middle of the transmission cross member. Put a little pressure on it, and remove the 4 15mm cross member bolts.

SLOWLY lower the transmission and transfer case, watch for binding or pulling of any electrical or mechanical connections, then remove the transfer case vent from the clips on the transmission.

Once you feel you can access the top nuts on the transfer case, remove the bottom 4 with the 14mm or 9/16" wrench. Loosen the 2 top nuts, but leave them started until you are completely ready to remove the case. A buddy is nice here, however the case is not too heavy and should be handled easily by one person (no problem for me, but I bench 240 so... haha)

Finish removing the top 2 nuts, and slowly pull the transfer case from the transmission. Be sure to place a pan under the tail of the transmission first as you will lose a bit of fluid.

Now that you have the 249 out, you can put a new output seal on the transmission, and hopefully by now you have your 231/242 ready to go with new seals. Swap the speed sensor and gear from the 249 into your 231, paying attention to it's position in the 249 case.

As Haynes would say, installation is reverse of removal. Be sure to fill with new fluid once it is installed!!!

Once you have the new case back in, it's time to decide if you need to adjust the transfer case linkage. Try and engage 4 lo. If you have an easy, full swing of each gear, then no adjustment is necessary. Most likely though, you will not be able to fully engage 4 lo. This is easily fixed. Put the shift lever in 2wd, then get under the Jeep and loosen the 13mm adjustment bolt on the shift linkage. Push the shifter all the way forward, and tighten the adjustment bolt. You should have full engagement of all gears now. If you have the new shifter gate or shift bezel, now is the time to install it. Take it for a test drive and be sure to test all the gears, then take it back to the shop and check for leaks. Check the fluid one more time, and correct any leaks that may be present.

VIC Plugs

For the lights in the VIC (Vehicle Information Center) to function properly with the new transfer case, it's as simple as a plug.

For connecting a two prong switch to a four prong connector, refer to this link:
http://www.jeepforum.com/forum/f13/transfer-case-swap-info-np249-np231-np242-685644/index40.html#post12051870

Start by removing the 4 screws holding the console bezel in place



Remove the 2 lights from the cigarette lighter and ash tray, and the power to the cigarette lighter.




Remove the three screws holding the VIC in place (two on top, 1 on the bottom) and slide straight out.



If you had the NP249, the red plugs should be connected:



Disconnect the red plugs, and dig in the wire loom until you find 2 black plugs. 1 female and 1 male, then connect them together.



The plugs should look like this:



Leave the red plugs un plugged, just as the black ones were, and again, installation is reverse of removal.



Good Luck!

[Jones]

Good work on the wright up. No pictures though?

[JrMechanic]

Yeah, I know

The Jheep is my DD, so I had to get it up and going. Honestly my hands were always full, and didn't have time to take pictures. However, I took the cheap road and neglected the output shaft seal on the transmission, and of course its got a slight leak (half dollar sized puddle over night in the snow), so I'll be pulling it back out again and I'll be sure to snap some pics.

[BLACKzj52]

did u swap ur VIC plugs?
just recently i took mine out to try and swap the plugs and cant find the red plug! its nowhere

[JrMechanic]

Yes, I did. I didn't see mine when I pulled the VIC, so I pulled the heater controls out and they were all tucked up in there. Red was connected, black was disconnected.

[CZAR]

I have the 231 in my 96 ZJ.

I have been seaching for the elusive 231 bezel...no luck.

Then....I had a thought. I wonder if a TJ or late model XJ shift handle would work? The t-case positions are indicated in the handle....not the bezel.

I'm doing some front end work this weekend & my buddies neighbor has a TJ. I'm gonna take a look & see what would be involved.

I'm certain it can be modified to work. Just not sure if it's worth the effort.

[BLACKzj52]

Originally Posted by CZAR

I have the 231 in my 96 ZJ.

I have been seaching for the elusive 231 bezel...no luck.

Then....I had a thought. I wonder if a TJ or late model XJ shift handle would work? The t-case positions are indicated in the handle....not the bezel.

I'm doing some front end work this weekend & my buddies neighbor has a TJ. I'm gonna take a look & see what would be involved.

I'm certain it can be modified to work. Just not sure if it's worth the effort.

iv got a 231 bezel

pm me if u want it, wont be able to ship it til maybe next weekend tho

Originally Posted by JrMechanic

Yes, I did. I didn't see mine when I pulled the VIC, so I pulled the heater controls out and they were all tucked up in there. Red was connected, black was disconnected.

i tried that too. my black one is connected tho.
this is all i saw when i took it all apart

[Jsun]

Originally Posted by JrMechanic

So if you have a 95-98 ZJ, get a transfer case from a 95-98. If you use an older input in a newer planetary set, damage will occur to the case.


Good Luck!

So does this mean I can only use t-case for theses years from a ZJ? or will this work from a XJ of the same years? If I have a older T-case, All I would need to do is swap out the input shaft?

Thanks!

[j.love]

John, I think the red connector in the center of the pic is the one you have to change.

[j.love]

Originally Posted by CZAR

I have the 231 in my 96 ZJ.

I have been seaching for the elusive 231 bezel...no luck.

Then....I had a thought. I wonder if a TJ or late model XJ shift handle would work? The t-case positions are indicated in the handle....not the bezel.

I'm doing some front end work this weekend & my buddies neighbor has a TJ. I'm gonna take a look & see what would be involved.

I'm certain it can be modified to work. Just not sure if it's worth the effort.

You can make your own from a XJ bezel. I did mine for the 249-242 swap.

Score an Xj bezel and cut up the plastic indicator, then place that in the center of your 249 clear bezel backing, then cut the scrap 249 black plastic to fill in the missing parts. Use a little black magic marker to black out the areas that will shine light threw, and then super glue it to the clear 249 bezel.

Its not perfect, but looks good for me.

[CZAR]

[QUOTE=BLACKzj52;6494909]iv got a 231 bezel

pm me if u want it, wont be able to ship it til maybe next weekend tho
QUOTE]


PM sent

[guther66]

Nice write up. Pics would have been nice, but oh well I had the 242 in my xj and swapped in a 231. I didn't really bother with any of the lights and stuff, no one else drives my xj. And I'll take it to its grave.

[BLACKzj52]

Originally Posted by j.love

John, I think the red connector in the center of the pic is the one you have to change.

nope that wasnt it. believe me i saw it and got real excited then it didnt look anything like the black one already plugged in

[JrMechanic]

Originally Posted by Jsun

So does this mean I can only use t-case for theses years from a ZJ? or will this work from a XJ of the same years? If I have a older T-case, All I would need to do is swap out the input shaft?

Thanks!

Any ZJ or XJ case from 98 and older will work... You just need to find one with the correct length input shaft as you cannot use an input shaft from say a 95 in a 93 case, due to the different gear cuts. You can swap annulus gears, but I believe thats around $150 for the correct one, and you should be able to find the correct case for that much, if not less.

John: The red connector in the center of the picture needs to be disconnected, and the black plug in the bottom of the picture needs to be plugged into it's other end.

[BLACKzj52]

Originally Posted by JrMechanic

Any ZJ or XJ case from 98 and older will work... You just need to find one with the correct length input shaft as you cannot use an input shaft from say a 95 in a 93 case, due to the different gear cuts. You can swap annulus gears, but I believe thats around $150 for the correct one, and you should be able to find the correct case for that much, if not less.

John: The red connector in the center of the picture needs to be disconnected, and the black plug in the bottom of the picture needs to be plugged into it's other end.

whhhaaatt?
dude that black connector u circled goes to the cigarette lighter thing.
the black plug on the bottom right most is the one that was plugged into my VIC