NP249 : NP242 Conversion
Written By: Brian Wesley Free
#1 Screw Extractor (It's a type of "Easy Out")
10" Monkey Wrench
8mm Socket & Crescent Wrench
18mm Socket & Crescent Wrench
9/16 Crescent Wrench (Buy a cheap one, this will be hacked)
9/16 Deep-Well Socket
Flat Head Screw Driver
Phillips Head Screw Driver
Gasket Remover or Razor Blade
Safety Glasses (Stuff WILL fall in your face & eyes)
Snap Ring Pliers (GOOD ones, Spend some money)
My 1993 Jeep Grand Cherokee V8 5.2
BEFORE YOU START:
Do your homework. I tried to make this write-up as conclusive as possible, but there is probably something I left out. This is not a factory service manual; do not treat it as such. This is just from my personal experience. I am not an employee of any off-road shop, parts distributor or parts manufacturer. I am a simple off-road enthusiast. This was done in my driveway, by my friends and me, your shade tree mechanics.
I swapped a NP242 from a 1991 Jeep Cherokee (XJ) into my Jeep Grand Cherokee (ZJ) with a NP249. The goal of this swap is to have the following capabilities: 2WD, 4 Part-Time, 4 Full-Time, neutral, 4-Low. I also wanted to do this swap because the 93-95 NP249 does NOT lock 50/50 in 4-Low. If you have a NVP249 from a 96-98 ZJ it DOES lock 50/50 in 4-Low. To make everything mate and mesh you have to remove the input gear from your NP249 and put into your NP242.
Chock your wheels, chock your wheels, chock your wheels. This means, put something in front and behind your wheels to keep your Jeep from rolling and moving any direction. Disconnect the Negative cable from the battery. Get in put it into neutral and pull the handbrake.
Removing the front and rear driveshafts.
The rear is connected to the differential with four(4) 8mm bolts. Unbolt these, and then slide the driveshaft out of the tailshaft of the transfer case.
The front driveshaft is connected in two places. Start by unbolting the four(4) 8mm bolts on the transfer case, then remove the four(4) 8mm bolts on the differential. Compress the front driveshaft, and slide it out.
Removing the crossmember and supporting the transmission.
Start by supporting the transmission. Using a bottle jack or floor jack place the top of the jack right behind the transmission pan.
Remove the four(4) bolts supporting the crossmember.
Remove the bolt running through the bushing that supports the transmission on the crossmember. After removing the crossmember support the transmission using the jackstand under the bushing housing.
Drain the transfer case. This is where your monkey wrench comes in handy. Notice the plugs.
Removing the transfer case.
Disconnect all the connections to the transfer case. The shifter linkage (The rod with the plastic bushing. It pushes through) and the electrical connectors, speedometer and VIC.
There are six(6) bolts holding the transfer case in place. You can't miss them. The first five(5) are easy to remove. The sixth one is on the top passenger side, it is a complete PITA. This is where your donor 9/16 crescent wrench comes in handy (And some of my redneck engineering). There is not enough clearance for you to put a full size 9/16 or even to use a socket. I had to cut the open end off of the wrench and notch the end to attach a piece of rope (The wrench ended up being a little longer than 4". Napa - $3.50 for wrench, $5.00 for some guy to cut it up). Loop the rope over the case and pull from the driver's side. It took both my friend and I to break this nut. (My knots: bowline on the crescent wrench end and two half hitches on the pipe wrench end. I didn't feel like busting it on account of my knots.)
This will take some effort. You need some muscle for this, or a really nice jack. I had the muscle and no jack. This takes two people. Both you and a friend need to wiggle the transfer case till you clear the bolts. If you have a creeper it will make things easier for you and him. Remove the case and place it on the creeper to pull it out from under the Jeep. I didn't have a creeper so my friend and I used a thick towel and placed the case on it to slide it out from under. Have a bucket ready. When you remove the case, a little transmission fluid will leak out of the transmission, so be prepared.
THIS CASE WEIGHS ALMOST 100 POUNDS, BE CAREFUL! I bench 225, this case is very big and awkward to maneuver so make sure you have everything in place and a plan between you and a friend, before you try to take it out.
The cases side by side. NP249 Left. NP242 Right. Note: I have yet to clean up the NP242.
Take a look at the inputs':
Before I cleaned up the NP242:
Breaking the case.
Start by removing the Speedometer gear so you don't damage it.
Remove the input seal and housing. It is RTV'ed. Then remove the snap ring on the input shaft. (Sorry bad picture. It is not the big obvious snap ring. It's the smaller one closer to the input gear.)
Next remove the three(3) bolts holding the back half of the tailshaft in place. This is also RTV'ed.
Next remove the snap ring completely from the mainshaft.
Remove the four(4) bolts holding the front half of the tailshaft in place. It's RTV'ed. Finally you get to pull the tailshaft off.
The next few pictures are pretty self explanatory.
Now you get to remove the back case half. Remove all the bolts holding it together. It is RTV'ed. Get out your flat head screw driver or crowbar. There are two outlets built into this case to help you break the RTV seal. One on both sides of the case.
Now remove the back case half.
(Take note to where everything is located so you can put it all back together correctly.)
Remove the chain just like you would on your bike. It's pretty simple.
Remove the mainshaft. This is what it should look like to this point.
Now to remove the shifter assembly (Inside the case). By the shifter there is a small rubber plug. Remove this plug and use a #1 screw type extractor to remove the low range shift fork rollpin. Tap the extractor into the end of the rollpin, and with vice grips on the extractor pull and twist in a counterclockwise direction to remove the rollpin. It may take 2 or three tries to remove the rollpin. If you cannot get the screw extractor to "bite", I had to drill out the rollpin, essentially shredding the rollpin inside the shaft. Then I punched what was left of it through with the 5/32 punch. You're going to have to go pick up another rollpin if you go this route. Pay special attention to the flats on the shaft when you remove it so you get it back in the same way. When you put this back together you'll need to reinstall this rollpin.
Give the input a slight tap and:
Remove the input gear out of the NP249. It's pretty much the same process as described above. With a few exceptions.
The tailshaft is one(1) piece on the NP249. This is where to access the snap ring. And you won't have to remove the rollpin on this one.
The input shaft I pulled from the NP242 on the left. Compared to the input gear that came out of the NP249 which is going into the NP242.
Put it all back together in the reverse process with your new input gear in the NP242. Make sure to clean out the inside of the NP242 before you put it back together. Clean all the surfaces with your gasket remover or razor and be very liberal with your RTV application (LOTS). Make sure to tighten everything down. Make sure to add one(1) quart of ATF or Differential Gear Lube to the case before you crank it up. I chose to use some AMSOil. Good stuff. Adjust your shifter linkage for the new case and you should be ready to roll!
Hope this helps anyone interested in performing the swap. If you have any questions don't hesitate to ask. If you do a swap using my write-up as reference, please, email me and let me know. firstname.lastname@example.org. Good luck!
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