I have a 1996 XJ with a NP231. My speedo and odometer were not working so I replaced the vehicle speed sensor. That didn't fix the problem so I got another speedo from the jy. That didn't work either. So I decided to pop the speed sensor out with the car running and spin the little shaft on it to see if the speedo worked. Sure enough it did. So, I now know that something in the transfer case is not working or gummed up. The question is, what do I do know? Do I have to take the tcase out and disassemble it or what? Please Help!! Thanks

 

Are sure that your cable did not brake of at the end,it is possible that just the end broke and a small pieace remains in the xfer case. I did not look at mine but there should be able to un screw the receptecale from the xfer case or a plate that can be removed,I just looked at mine and where your cable screws in can be removed,it appears to be a 13mm bolt that holds it in,then then it can be removed where you can inspect the worm gear and drive gear for damage

 

I a a little confused here. You have a speedometer cable right? If so, and you are sure the cable is not broken, then try to rotate the speedo gear inside the case. It should not turn. If it does, then remove the speedometer gear assembly. This assembly comes out by taking out one bolt. Make sure you mark the position of the speedo gear assy before you remove it. When you look inside you should see a worm gear on the shaft and then the plastic gear that is turned by it.

 

I have an electronic sensor, not the speedometer cable. It is pretty much identical to the one shown in this picture in the upper right.

 

Does anyone have a schematic or manual for the np231. I'm thinking I'm gonna have to take it apart to find out whats wrong. Any other ideas?

 

Is it clocked properly for the tooth count?

 

I'm still not sure exactly what is the problem, but If I could remove the speedometer adapter from the transfer case to inspect the gear that would probably be a step in the right direction. However that thing is VERY stuck...The adapter that I'm talking about is shown below. However mine seems to be a permanent part of the Xcase

 

Well, if yours has been in there long enough to "become a permanent part of the transfer case" then it is most likely bad.

 

Found out a couple of interesting things today. First, it seems that my jeep originally came with an NP242, as the driver side visor gives a breakdown of the "selec-trac" system. However, I very clearly have an NP231 according to the tag on the xcase. I wish I knew more details about that swap, but it seems ok as everything seems to drive fine. Second, I finally got the speedometer adapter off of the xcase and there was no speedo gear in there at all. That would probably explain my lack of speedo readings! However, the fluid inside of there is pretty thick and dark brown which can't be good. Should I get it flushed, or should I just try to get most of it out and change the fluid? Thanks for your help. Here's some pics of the mess I found! Second pic is inside of the xcase where the speedo adapter came out.

 

wow, i have never seen that before. I would say flush as much out as possible, looks like mud in there.... lol

 

My 00 XJ has the select trac information on the visor even though the thing has a 232. If you want a good tear down schematics then look for a Haynes manual. They have a decent tear down info. Otherwise you will want to look into buying a year subscription to Mitchell on demand for your vehicle. Other then that it needs to be timed to the specific tooth number on the gear and the side of the gear assembly. You will see it on the side of the black housing...three sets of numbers that you will need to match to one of your gears tooth count( everything is labeled on the sides and on the gear). Other then that good luck and let me know if you have anymore questions.

 

I got this jeep about a month ago from a bail bondsmen who took this jeep as payment from a 19 yr old kid who couldn't post bail. He said the kid had taken it mudding the day before and it was pretty much covered in mud. It then sat for three months caked in mud at this guys house. I think that might explain the condition of the tcase. Surprisingly the thing runs awesome and hasn't missed a beat. The underside is pretty bad though, and I had to patch about 6 holes in the floor. I'm slowly restoring it to its former glory, but keep uncovering gems like this one!

 

Nice macro images- Get the pinion(speedo gear) that you need based on your gear ratio and tire dia. Empty and refill your transfer case-run it long enough to get it nice and warm- drain and refill it again! Run that for a few days and check the fluid to see what it smells and looks like. If everything seems to be acceptable and your speedo works properly go with it and do regular maintenance as called for! If your drains contain excessive amounts of metal, you may have to invest in a rebuild. Good luck

 

I have a similar issue with the speedo on my '96 Cherokee. It just recently began jumping back and forth between say, 5 and 55 - but happens more when it is first started. It continues for awhile and seems to settle down after about 10 miles or so, but I was wondering what the problem might be. I had something similar happen to another vehicle in the past, and it was the alternator. Any suggestions? I have the NP 231 TC, btw.

 

The inside almost looks like someone had put 75w90 in there instead of ATF+4! I would do a couple of fill n drains! Fill it up drive it for like 10 miles and drain and refill! keep looking at the inside to see the progress of changing it! Make sure you also get another o-ring for the speedo sensor! you'll need it!

Aaron