xj to mj

[drew91xj]

hi guys will be picking up my first mj soon, its a 1990 4x4 lwb, many questions being this is my first mj build first off.

 

what will and what won't swap from my 93 xj to the 90 mj?

 

second the mj will be a rolling chasy what exactly do i need to swap over to put my 4.0 h.o. into the mj,? i was told the entire harness from head light to tail light is this correct or is there a simpler way to do it, the tranny will be a aw4 and a 231j transfer case if that helps.

 

if i swap everything do i have to use the xj gas tank and sending unit being it will be moved to the bed.

 

also i have been thinking about building long arms for my xj will they work on the mj i.e. is the crossmember and tranny mount the same as the xj?

 

any advice is greatly appreciated i'm sure i will have other questions along the way.

thakns drew

[Hawk]

First, welcome to CC. You'll find a wealth of information and friendly advice here.

 

I'll answer your questions as best I can, in order....

What will and won't swap-

The MJ rear leaf springs are longer than XJ rear leaf springs.

The XJ gas tank will not work, since the MJ tank is in front of the axle, under the drivers side of the bed. The fuel pump and sender in your MJ tank will work fine though.

 

As far as swapping the driveline, you'll need a new rear driveshaft, but I think the front is the same. You may as well swap the harness, it's not that hard. Some of the sensors might be different, and you'll probably want to use the gauge cluster out of the XJ.

 

XJ and MJ front suspension is identical, so yes, your crossmember, long arms, etc will all work on either.

[mvusse]

XJ fuel sender is mirror image of MJ. If the MJ has an internal pan inside the tank, as all stock and some after market tanks do, an XJ sender unit will not work. It interferes with the side if the pan. It may work in an after market tank without a pan.

 

Yes, parts stores show them as being interchangeable. Parts stores are wrong.

 

Correct MJ fuel sender units are not being produced any more.

 

Pumps are the same, for the same engine. HO pumps is not the same as Renix pump. HO sending unit is not the same as Renix sending unit. It reads backwards and is not calibrated the same.

[Geonovast]

You will need to swap over the engine bay and dash harness, you will have to use the XJs gauge cluster. For the most part, it will be like pulling it out of one XJ and putting it into another. Engine bay/front suspension/dash between XJ and MJ is the same, unless the MJ was an automatic and has a column shifter.

 

ALL XJ/MJ crossmembers are the same.

 

The XJ tank will work if you put it in the bed. I have done that exact mod and works fine. However, the MJ sender will not work properly. It will send fuel and the motor should run, but the Renix and Chrystler level senders are different, and using a Renix sender on a Chrystler system will make your fuel gauge read incorrectly. If you plan on keeping the MJ tank, you'll need to get ahold of a very rare 91 or 92 MJ sender.

 

 

Does the MJ have driveshafts? If it was originally a 4.0 auto 4x4 then the rear shaft will work. Otherwise you'll need to have it lengthened/shortened.

[drew91xj]

well so far i am happy with the response and friendly ness, maybe when I'm all done with this some of us locals can get together and wheel, well the plan was to swap the dash and harness ext ext. i will be moving the xj tank to the rear of the bed and using the xj harness sending unit, pump this should work shouldnt it?

 

also the leafs i figured were diffrent hoping to do an 8.8 swap when i swap my lift coils over and do a soa swap.

 

i will need to locate a rear drivshaft for it being i have three front ones i can use.also

 

another question will my 93 tranny hook up to the colum shift linkage that will be going into the mj or should i just swap in the xj floor shifter? if needed to swap how hard might this be?

 

i feel i am fairly mechanicly inclined for my age being i am only twenty and have wrenched on everthing i have owned which consist of three jeeps now my chevy truck and familys and friends vehicles

 

thanks for the advice, knowledge will try and keep updated when it arrives and i start working on it

drew

[Geonovast]

I believe the column shift should hook up to the 93 trans, however I would swap the XJ steering column in and use the floor shifter. The 93 gauge cluster will not have the shift indicator, you can't just throw it in without modification. When you swap it, just put it in like it's in the XJ. The hole for the shifter will be there, just plated off.

[Eagle]

I believe the column shift should hook up to the 93 trans, however I would swap the XJ steering column in and use the floor shifter. The 93 gauge cluster will not have the shift indicator, you can't just throw it in without modification. When you swap it, just put it in like it's in the XJ. The hole for the shifter will be there, just plated off.

:agree:

[drew91xj]

ok swaping the shifter sounds easy enough never thought about the gear indicator not being there thakns guys will keep up to date

[drew91xj]

ok got the mj the other day gutted the interior yada yada while looking under neith the mj i noticed on the unibod section where the crossmember goes it has like a 1/2" lip the comes off the bottom of the unibody rail, with that said how will the long arms kits like rustys offroad and rk work with that being there is a lip there which will not allow it to mount flush. maybe I'm over looking somthing idk, but i'm looking into getting long arms and don't want to buy somthing that won't work. anyways thats all ?'s for now, also any one post pics of tube/pre runner bed ideas or things they have seen, i will also serch judt easier to ask

[Automan2164]

:popcorn: I am defineatley keeping my eye on this thread. Believe it or not, I have a '90 LWB MJ with a bad 4.0L, and just picked up a '93 XJ with a lift and good drivetrain. I too, will be swapping out everything from the XJ to the MJ. Harness complete. As soon as I sell some crap, I am going to kick it off. Maybe we can help each other along.

 

Rob L.

[drew91xj]

what a coinsdence (sp) thats funny yeah that sounds good i havnt started the motor stuff yet but will be this winter I'm doing body,paint and tube work done while its nice and beating on my xj until then. then this winter i will pull both into the garage and start tearing everything out let me know how the wire swap goes being that is the one thing i am kinda dreding but i was told it was pritty straight forward. good luck with your build throw a few pics up if ya get any and ill try and do the same.