Jeep Cherokee XJ - NP231 Transfer Case Fluid Swap

While doing regular fluid maintenance on the transmission, the transfer case should be serviced as well. I mean, it's right next the transmission, might as well change out the fluids on it! It's a really easy job, and takes about as long as it does to swap out the transmission fluid.

The NP231 Transfer Case

My Jeep has the NP231 transfer case. I know this because I have the following settings on my shifter:

2H, 4H, N, 4L

Also, any 5-speed Jeep Cherokee XJ from 1987 to 2001 was manufactured with the NP231. From what I've read, this is a very well-built transfer case, and I want to keep it that way for the life of the vehicle.

Using the Proper Fluids

The NP231 has a capacity of 1.0 liters (2.2 pints). It is recommended to fill it with any Dexron III or Mercon automatic transmission fluid. Since I was filling up my transmission with Red Line MT-90, I decided to stick with Red Line fluids all around. I ordered two bottles of Red Line 30504 D4 Automatic Transmission Fluid. It's good for use in Dexron III and/or Mercon applications, so it works with my NP231 just fine!

Draining and Filling

The first step is to remove the fill plug. It's up higher on the front of the transfer case. Undoing both plugs will require a 10mm allen wrench. If the transfer case hasn't been serviced in awhile (or ever), be prepared to use some muscle getting the plugs out. Remember to apply heavy, but gradual pressure.



Before removing the drain plug, place an oil pan underneath the transfer case to catch the old fluid. When the drain plug is removed, the fluid will flow right out. Once all of the old fluid is out, put the drain plug back on.



Using a fluid pump, begin refilling fluid through the fill hole. Be patient, depending on the pump, this could take quite a bit of time.



Continue pumping fluid in until it starts overflowing from the fill hole. At this point, put the fill bolt back on and tighten it. I don't remember the torque specs, but use your best judgement.

Congratulations! The transfer case has fresh new fluids in it. Happy wrenching!