carfreak1989

just blew up my planetary for 4 low today my buddy has a np231 laying around. will it bolt right in? thanks for your time,

firstime00XJ

We need a little more information, like what transfer case you currently have.

carfreak1989

its the stock t case out of a 93 grand cherokee. i believe its the 249

thanks

ROCK

Would help with a lot more info, but here goes. 231 is a direct bolt in, but the gears could, and most likely will be different. There was a gear cut change in 96, so any case made before 96 will have the old cut, and visa verse. If you need to change gears you will have to be very careful to get the right years or it will scream like a banshee. If you have a 4.0 and an automatic you can get a 231 out of basically any Cherokee with the same drivetrain and it go right in. If the donner case is from a manual trans you will have to change gears. If you have a V8, you will have to change gears. In a Grand you had 2 case options, 242, or 249. The gears out of ether one will go in the 231, so it's as simple as swapping your gear into the donner case. Your linkage will be a bit different, but that's simple. Take the wing off your current case, and put it on the donner case. Also, make sure your donner case has the same out put shaft length, if not you will have to shorten your drive shaft.

Post up all the info on your Jeep and I'll tell you every thing you need to know. I have done so many of these I can swap gears in 12 minutes!

carfreak1989

wow well i guess im talking to the right person.

1993 jeep grand cherokee 4.0l automatic quad-trac 3 inch lift rear aussie locker on 31's. the t case is out of an 04 tj with a 4.0 auto. thanks for the help

ROCK

It should go right in. Your sensors will be different, so the lights on the dash/shifter will not work. Other then that, and the rear slip yoke you should be ok. Newer cases have external slips, and older have internal slips. If the spline is the same you should be fine, just might be hard getting the boot over the bigger slip on your shaft VS the smaller one from the TJ. If by chance you do have an internal slip on the new case(rare) just make sure the seal is the same so it doesn't leak.

I have a 95 GC, and have been threw a few cases. My first 231 is hanging on the "wall of shame" in my garage. I blew it in half! I now have a 241 DLD out of a 3/4 ton dodge.

carfreak1989

ok cool thanks for all the help i cant wait to fix her up and hit some more trails. thanks again

xjoffroad

you keep saying gears what gears? the input output shafts? and no its not as simple as '"swapping gears" like you say.

xjoffroad

here's a write up a buddy did while we swapped his case. its more work then swapping gears.

So now I have my 231, what do I do with it?
Start by taking out your old 249. I find it easiest to drive the ZJ up onto 4 ramps when doing t-case work, or putting it on a lift. Be sure you are in 4WD if you pull up onto the plastic ramps though. It’s very hard to push the front tires up onto the ramps and you don’t want to shoot the ramps out from under the rear tires. Don’t ask how I know this!

It helps to have some people helping, as the t-case is pretty heavy and not fun to maneuver by yourself. So raise the vehicle and secure it in place with the e-brake (putting it in park will obviously not work as you are removing the drivetrain!) and other methods if you so desire.

- remove front and rear driveshafts (fluid will probably leak out the rear output when your pull the rear shaft, so you may want a drip pan)

- place a jack under the tranny pan using a block of wood or some other method to keep from damaging the pan.

- Disconnect all hoses, linkage, and other fittings on the t-case

- Drain the fluid of the 249 (30mm socket or wrench to open drain plug)

- Remove the 4 bolts holding the crossmember to the frame rails (be sure your jack is holding up the tranny and t-case or things will get very bad VERY quickly)

- SLOWLY lower the jack under the tranny pan until you can access all 6 nuts holding the t-case to the tranny. These should be 9/16” or their metric equivalent. They are a MAJOR PITA to get to, so be patient. Leave a couple bolts on the mounting studs to hold the t-case on until you’re ready to yank it. Raise the jack back up once you have the upper bolts removed

- Using a tranny jack or pure muscle, now remove the t-case from the tranny. You will need to slide the t-case back, and then it will come down. Tranny fluid will probably leak out a little bit, so again a drip pan is a good idea.

NOTE – on some models the tranny mount may be in the way of some of the nuts holding the t-case on. In this instance, remove the crossmember from the tranny and set it aside.


So now you have the 249 out of the vehicle, how do I get all this stuff back together??

Now that the case is out of the vehicle, you can examine the input gears to make sure they are the same length. If they’re different, don’t fret too much. This is where a Factory Service Manual is worth its weight in gold. You’ll need to tear down both cases and take the input gear from your 249 and put it in the 231. It will work, assuming that the gear cut is the same. There was a change in gear cuts around 94-95, and the gear cut MUST match what the case originally had in it, or again, very bad things will happen very quickly. The difference in gear cuts is easily identifiable simply by looking at the two input gears. If the cut of the gears looks different at all, time to look for a new input gear. I’d avoid the dealer, as you’ll pay more for the input gear than you probably paid for the whole t-case. I found one at the same tranny shop that had the correct output yoke. It ran about $150, which still isn’t cheap, but it’s half of what the dealer wanted.

Personally, I would rip down the 231 regardless if I was swapping input gears. It’s a good idea to do a full rebuild on it, or at least clean it out and get an idea as to what goes on inside of the t-case. Once again, the FSM is a great tool to have for this.

One other step that I would take before putting everything back in is getting the proper shift linkage for the 231. The tab that bolts to the outside of the case is probably going to need to be changed. It’s a cheap part, dealer only. Order the part for a 93 ZJ with a 231, you’ll need a case ID# too. The one I used that I found on here is 5209 8319. Simply unbolt the old tab, and put the new one on. Your factory linkage may need to be lengthened or shortened, but with this tab the linkage will work without any major modifications.

So now you’re 231 is ready to be installed!

Simply reverse the steps you took to remove the 249 and you’re good to go! Don’t forget to put new fluid in your 231 if you haven’t done so already.


Double and triple check everything to make sure you’ve got it all tightened up and ready to go before driving the vehicle. Don’t go right out onto the highway, tool around on side streets for a bit to make sure everything is working properly.

Here’s a brief summary of issues that I ran into with the swap, and how to solve some of them:

Input Gear
Needs to be a 23 spline, but the length is not known until the case is actually removed from the Jeep. You can make an educated guess as to what it will be, but there is no for sure way of knowing what it is. Usually you can swap the input shaft from the 249 into a 231, but there was a change in the gear cut right around 94 or 95. I got my case from a 90 YJ and needed to swap input shafts. The one from my 249 (1995) was the wrong gear pitch, which would've seriously screwed up the t-case. I had to purchase a new input gear to match the t-case and tranny. They are NOT cheap!! I paid more for that gear than I did for the whole case. The original 231 I put in has since been retired due to the front driveshaft coming apart and knocking a hole in the case, and the 231 I replaced it with already had the correct length shaft on it. So . . . I have two spare input gears for jeep t-cases. Both are the longest there is, one old gear cut, one new. If you do the swap and run into the same problem I did, and need a long input gear, let me know!!

Shift Linkage
More than likely will not work correctly. I can't remember the correct name for this part, but there is a tab on the outside of the case that the linkage hooks into. All you need to do to correct the linkage is get a new tab. It's hard to describe in words, but I'll see if I can find a pic of it for you.

Vehicle Information Center
I personally did not solve this "problem" as I know when I'm in what mode on the case. Apparently you can change the wiring up a bit and this will work, but I haven't messed with it at all.

Shifter Bezel
The "diagram" next to the t-case shifter will obviously still be for the 249. If you want to replace this a FEW early ZJ's with the 4.0 came with a 231 and you may still be able to order this part, or the bezel from XJ's might fit there too. Again, an "issue" I didn't deal with.

Front Output Yoke
Depending on what vehicle you source your 231 from, you may run into this problem. I got mine from a YJ and YJ's use a single u-joint at the t-case end of the front driveshaft, whereas ZJ's, XJ's, and TJ's all use a double cardan joint.

ROCK

Great wright up. Im talking about the input gears. It is really simple if you know what your doing. The gears are pretty much all the same as far as gear cut goes in side the planetary. There are several spline counts, lengths, bearings, and seals. The input gear from the 249 will go right in the 231. You may need to change the bearing, but that's easy. pop one out, and the new one in. You may also just change the entire planetary set up. one comes out, the new one drops in.

Im sorry if I made it sound easier then it is. For me, its simple. I can do an input gear swap in 12 minutes. Im sure most people who have never had one of these cases apart could do it in under an hour.

xjoffroad

also the shafts are different lengths so we have had to shorten a few of them for this upgrade