A lot of this write up is taken from nierace 247 to 242 write up as it is very similar. Information on swapping input shafts can be found here: http://www.mallcrawlin.com/forum/showthread.php?t=10254
Llet me know if you see anything incorrect and I will correct it. Thanks
1999-04 Jeep Grand Cherokee WJ Quadra-Trac/Quadra-Drive to 231
(NP247 -> NP231)
231 (Mine was out of a 94 YJ. From what I read, that is cut off year that you can swap input shafts from the 231 as before that, the gear cut is different. Rear output needs to 32 if you don't run a sye eliminator. I am using a sye eliminator so rear spline count isn't important.)
2 quarts of ATF
1/4” Ratchet set
Short 1/4“ extension
14mm or 9/16” deep socket
14mm or 9/16” regular socket
14mm or 9/16” wrench (ratcheting wrench highly recommended)
12mm regular socket
8mm regular socket
10mm Allen key
Slotted screw driver
Jack stands (optional)
1.) Depending on the rig you are working on you may or may not want to put it on jack stands.
a. If you have a 4” lift you will have enough room to work underneath on level ground, if not I would recommend putting it on stands.
b. Putting it on stands will also make it easier to take off the drive shafts.
2.) Once on stands and you have a transfer case skid plate, you will need to remove it. The stock one uses 3 bolts on the cross member, and 2 on the unibody.
3.) You will now need to drain the transfer case fluid.
a. Place your oil bucket below the drain plug.
b. Using a 10mm Allen key remove the fill and drain plugs.
c. Clean them and put them some where safe.
4.) While the transfer case drains remove the rear drive shaft.
a. Using a 1/4“ ratchet, extension and 8mm socket, remove the bolts and the straps on the universal joint at the differential end of the rear drive shaft. Place them in a safe place.
b. Use a mallet if needed to knock the u-joint out of the yoke on the rear differential.
c. Once freed pull the drive shaft out of the slip yoke end of the transfer case. Place some where safe, though it will not be re-used.
5.) Remove the front drive shaft.
a. Using a 1/4“ ratchet and 12mm regular socket remove the bolts from the front output of the transfer case to the drive shaft.
b. Use a mallet if needed to knock the u-joint out of the yoke at the transfer case.
c. Once free you can rest the drive shaft on the cross member as you will be re-using it.
6.) Lower the cross member so that you have room to work.
a. Use a floor jack to support the center of the cross member, jack it up so there is some pressure on the floor jack.
b. Remove the bolts.
- Use 15mm socket on the bolts.
- I have Claytons LA’s, so I use 14mm sock and wrench.
- Place the bolts/nuts in a safe location.
c. Carefully Lower the cross member 1-2” ***Do not drop it lower***
7.) Remove shifter lever cable and bracket.
a. Pop the cable end off of the lever at the transfer case, you should be able to use your hands, if not use a slotted screw driver to pry it off.
b. Using 14mm socket remove 3 bolts located on driver side on the transmission. (Diagram 1.4)
c. Using a large wrench, put the bottom jaw on the bottom of the bracket, then the top jaw on the lip of the spring clamp holding the cable in the bracket. Apply pressure and it will pop right off. (Diagram 1.5)
d. Put the cable through the bottom hole, then put the spring clamp back on.
Diagram 1.5 - In original position:
Diagram 1.6 – In new position:
8.) Remove transfer case nuts.
a. Clean off the showing thread and soak in penetrating oil or WD40.
b. Use a combination of the 14mm deep socket, regular socket and ratcheting wrench.
c. The reason you will need the short sockets is there is not much room once you start to unthread the nuts on some of them. So you need to swap out or it will get stuck and you wont be able to get the wrench/socket out.
d. Be very patient as you will be doing a lot of 1 click ratcheting.
e. Clean the nuts thoroughly.
9.) Once the bolts are out, remove the transfer case. Having another person would be helpful, it weighs 80lbs so you should be able to manage it on your own. Place in a safe place.
a. Check your transmission output seal and replace if needed.
b. Check your breather tube to make sure its not split, if it is, cut off the split section and connect a new piece.
1.) Lift up and line up the 231 with the bolt holes in the transmission mount.
a. You may need to rotate the input of the transfer case to line up with the transmission for it to slide in.
b. Once all the way in, it will be able to support its on weight.
c. Put the transfer case nuts back on, and use anti-seize.
2.) Once the transfer case is in position, bolt the shifter cable bracket back up.
a. Reinstall the 3 14mm bolts.
b. Cut the 231 shifter in half and cut the 247 shifter at an angle to move it 3/4" back. This is what it should like.
c. Install the modified shifter.
d. Clip the end of the cable onto the transfer case shifter, you may need to use a pair of pliers to pop it on.
3.) Bolt the cross member back up. Torque the 15mm bolts to 30-34ft lbs
4.) Check to make sure that you can shift correctly. If you cannot, you need to modify the shifter.
5.) Reconnect the front drive shaft. Apply lock tite on the 12mm bolts then tighten.
6.) Connect the new rear drive shaft.
a. Slide the transfer case end into the slip yoke. You may need to rotate it so the splines match up.
b. Place the differential end back in the yoke, put the u-joint straps on, apply lock-tite to the 8mm bolt then tighten.
7.) Drain any remaining oil in the NP231.
a. Place your oil bucket below the drain plug.
b. Remove the fill and drain plugs.
c. Let what ever is in it drain out, then reinstall the drain plug.
d. Now use 2 quarts of ATF to fill the transfer case.
e. Reinstall the fill plug
8.) Reinstall skid plate.
9.) Remove jack stands.
I used a label maker to mark my shift points.
Expect to spend approximately 4-8 hrs to complete this swap.