MJ upgrade

Milt51 · Apr 27, 2013

I'm sure this topic has been covered before, but I would appreciate some fresh input. I have an 89 MJ 4.0/AX15/231/d44 (big ton package) runs and drives, but someone has had a heyday with the wiring

, I also have a donor 93 ZJ with bad AW4. Considering swapping the HO with harness, the 242, and the non cad d30 into the MJ. The 3.55 gears will be decent improvement over the 3.07s, and I hear the Chrysler system is a vast improvement over the renix. Any suggestions / warnings?

cruiser54 · Apr 27, 2013

Lotta work. Chrysler system is not a vast improvement.

xjtrailrider · Apr 27, 2013

Milt51 said:
I'm sure this topic has been covered before, but I would appreciate some fresh input. I have an 89 MJ 4.0/AX15/231/d44 (big ton package) runs and drives, but someone has had a heyday with the wiring, I also have a donor 93 ZJ with bad AW4. Considering swapping the HO with harness, the 242, and the non cad d30 into the MJ. The 3.55 gears will be decent improvement over the 3.07s, and I hear the Chrysler system is a vast improvement over the renix. Any suggestions / warnings?

The front axle is worth swapping. I "think" the 242 will work(what is the spline count on the 93 242?). Find a XJ 8.25 rear axle(97-01 will be 29 spline and very strong). Cut the spring perches and if you want to lift your MJ then go spring over, if you want to keep it stock, stay spring under.

The engine can be swapped and still use the RENIX system, search the threads, the info is in here.

As for the wiring, just find a well kept 89-90 XJ in the JY and pull the wire harness out of it, swap it in.

Sell your D-44 and pay for all of the upgrades. People give stupid money for those axles

cruiser54 said:
Lotta work. Chrysler system is not a vast improvement.

I couldn't agree more

Mnkyboy · Apr 27, 2013

cruiser54 said:
Lotta work. Chrysler system is not a vast improvement.

X2 the HO makes a little more power but thats mostly due to the head and intake rather then the ECU. the Renix is a very simple and reliable system so the Chrysler stuff wouldn't be much of an upgrade.

If your set on it I would use an XJ harness rather then the ZJ. The MJ engine harness ties in differently to the cab harness then the XJ or ZJ but there are write ups with all the pin outs and info for swapping the XJ harness into an MJ. I doubt you will find that for a ZJ so you will have to figure it out on your own.

What's wrong with your current wiring? If the truck runs good it might be easier to clean up what you have.

Also FYI, ZJs are low pinion and most use CV shafts so the axle would be a down grade on your MJ. You could however use the shafts from it to delete the CAD in your current high pinion 30.

Also depending what you plan to do with the truck the 231 is stronger then the 242.
Are you sure you have an AX15? 89 was the split so some have it but a lot have the BA10/5
The 242 might fit the AX15 but the BA10/5 IS 21 spline so you would need a new input on the 242. Also note that ZJs use three different spline lengths on the t case input shaft so you may have to change it anyway.

cruiser54 · Apr 27, 2013

Cruiser’s HO into Renix Swap
This swap is easier than some will lead you to believe, generally those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.
The HO and Renix have some differences but none that can’t be overcome very easily.
Any HO engine from an XJ or ZJ through 1999 can be used. One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from the HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head for the sender.
You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use the Renix gasket. Exhaust ports are identical.
You will need to use your Renix distributor as it is different than the HO because they use different fuel management systems. The flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.
The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16" square drive or a modified 3/8" drive that has been ground down to fit. Do this before installing the engine.
As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.
　
Revised 03/28/13
　

YELLAHEEP · Apr 27, 2013

If your '93 ZJ has a factory security system......... that can wreak havoc with a swap as well.

MJ upgrade

Milt51

NAXJA Forum User

cruiser54

NAXJA Forum User

xjtrailrider

NAXJA Forum User

Mnkyboy

NAXJA Forum User

cruiser54

NAXJA Forum User

YELLAHEEP

NAXJA Forum User

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