5.9L MJ Build.....

So it's been a loooonnnggg time since I've posted on . Some of you may have remembered my previous XJs. The last one was a 2 door, black 99', 35s, etc... After stepping away from Jeeps for 2 years and having Land Rover's and Yota's I'm about to come back full force. If all goes to plan I should be picking up 90' MJ Eliminator tonight :roll:. Needless to say, I'm stoked!

The truck is bone stock, unmolested. Straight body, no rust, Renix 4.0L, AW4, NP231, HP30, D35, 190K. Eliminator interior = bucket seats, center console, floor shifter, full guage set.

I'm putting together preliminary plans now for a build. I need to brainstorm some ideas by you guys regarding the engine/tranny before any final decisons are made.

I have a access to a complete running 98 ZJ 5.9L that was wrecked in the front that I can buy for ~$700. I'm confident I could sell the body parts and interior pieces off to possibly break even.

My questions are how feasable would it be to swap the 5.9/46re from the ZJ to the MJ. I realize motor mounts would need to be made, but my main concern is the electrical. Since I have the complete jeep can I reuse the complete wiring harness from the ZJ or should I contact a company like Painless? The last thing I want to do is get the engine/tranny swaped and not be able to get it to run properly. If I'm correct the guages wouldn't work from the MJ with the ZJ engine? If not, I was thinking of running an autometer set up in place of the stock guage cluster. Is this possible?

Also, I'm 99.9% sure a 231 will mount to the 46re with an different input shaft?

Thanks for any help!

Np231 shouldn't be a problem. Dodges came with the 231 mounted to a 46re all day long. You are correct in that the input would probably be the only thing to change, if you had to change anything at all.

P.S. Welcome back to the scene fellow MJ member..............:cheers:

Check the external dimensions of the 5.9 - I think it's even bigger than the Chevy engines, which are themselves a shoehorn-fit sort of deal when swapped into XJs. Its cluttered enough with the 4-oh... Make sure it will physically fit.
From there, you are looking at aftermarket guages or retroing the stock ZJ guages to fit I'd guess. Can't think of any reason not to use the ZJ harness.

That would be a mean 'manche.

It will fit, the 5.2 and 5.9 are the same block IIRC. Here is a 5.2 Magnum XJ.



Wasn't paying attention before as far as reusing the MJ's 231. Yes, just grab the 23 spline input out of a later Jeep and it will bolt right in.

Kittrell said:

It will fit, the 5.2 and 5.9 are the same block IIRC. Here is a 5.2 Magnum XJ.

Wasn't paying attention before as far as reusing the MJ's 231. Yes, just grab the 23 spline input out of a later Jeep and it will bolt right in.

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I have read through some of your posts. Do you have a link to your swap/build?

What wiring harness/guages set up did you use?

Ha, that is actually not my build. I'm just sort of a connoisseur of information. Locally I'm known as the Encyclopedia Jeep, 90s Edition..............

I'll research your project when I get off work today and see what I can come up with..............:thumbup:

more of a hassle wit 360motor. Chevy motor is easier to put in and has more aftermarket. I know people wanna keep the chrysler with the jeep but its just tougher.

Kittrell said:

Ha, that is actually not my build. I'm just sort of a connoisseur of information. Locally I'm known as the Encyclopedia Jeep, 90s Edition..............

I'll research your project when I get off work today and see what I can come up with..............:thumbup:

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Cool. I thought it was another member's build, I just can't remember his name. Thanks for you time and any help. I really feel it's possible IF the wiring is not a nightmare.

On a side note I found one company www.backwoodsoffroad.com that builds harnessness for the Tj's to swap in 5.2/5.9L Mopar engines. I am going to try to call them to see if they could build one for my MJ.

I still think it may be easier just to do all new guages and a custom overlay in place of the factory guage cluster.

projectTK said:

more of a hassle wit 360motor. Chevy motor is easier to put in and has more aftermarket. I know people wanna keep the chrysler with the jeep but its just tougher.

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What makes the 5.9 any more difficult than the 5.2? The blocks are physically the same. The 5.9 is essentially a stroked 5.2.

Nothing that I can find. They are the same size. Larger bore and stroke on the 5.9L. I don't think fit will be the problem. My main concern is wiring.

Yeah, the 360, 318, and 273 all have the same external dimensions.

This is mostly relating to the older LA blocks, and not the newer As. But the blocks are essentially the same. Mostly just looking at carbureted vs. FI. A good link nonetheless, most of it still applies.

http://www.allpar.com/mopar/4bbl.html

I'm having trouble really finding much of anything at all. The question has been asked a few times, and thats about it. I know at least one has been done per my picture, but the people doing it are just not taking the time to do a write-up. If there is a build thread for that blue XJ, I have never been able to find it. It's been so long, but I am pretty sure I swiped that off of ebay. The seller never returned my specific info request as I was obviously not interested in buying the rig. Though that isn't as bad as the one time I caught a rig on there with a mod I liked. I inquired to the seller about how he did it. And he wouldn't tell me, but he'd have no problem building it for a cool $400.

To me, I see the ZJ dash as being mostly digital, much like the 97+ XJs. I think it would be easier to swap in the newer dash and use the whole ZJ harness. Though if that place can build a harness for you (I'm sure they can, I'm sure it won't be cheap). Then I would save up the change and go that route to bypass a crap ton of headache, and a possible never ending game with electrical gremlins. You can do a custom on your own, but you really have to know what you are working with and should be fairly proficient in wiring things in general. At the same time, that is obviously an old renix rig, so they might have found a work around. With the old LAs being carburetors and completely mechnical, there could be some pieces out there to make it all work.

Kittrell said:

I'm having trouble really finding much of anything at all. The question has been asked a few times, and thats about it. I know at least one has been done per my picture, but the people doing it are just not taking the time to do a write-up. If there is a build thread for that blue XJ, I have never been able to find it. It's been so long, but I am pretty sure I swiped that off of ebay. The seller never returned my specific info request as I was obviously not interested in buying the rig. Though that isn't as bad as the one time I caught a rig on there with a mod I liked. I inquired to the seller about how he did it. And he wouldn't tell me, but he'd have no problem building it for a cool $400.

To me, I see the ZJ dash as being mostly digital, much like the 97+ XJs. I think it would be easier to swap in the newer dash and use the whole ZJ harness. Though if that place can build a harness for you (I'm sure they can, I'm sure it won't be cheap). Then I would save up the change and go that route to bypass a crap ton of headache, and a possible never ending game with electrical gremlins. You can do a custom on your own, but you really have to know what you are working with and should be fairly proficient in wiring things in general. At the same time, that is obviously an old renix rig, so they might have found a work around. With the old LAs being carburetors and completely mechnical, there could be some pieces out there to make it all work.

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First off thanks again for you time and help. iIstill haven't given up. I'm going to keep digging. From a few conversations I had today with wiring/harness companies, including painless and backwoodsoffroad. It can be done but I will basically need 2 systems.

A stand alone PCM that manages the engine/tranny and a second system that converts to my guages. The problem seems to be finding a company that can flash the ZJ PCM to get rid of all the sensors that I won't need on the MJ. Also, the 46re is electronically controlled, which poses another problem. IF I can find a 46rh, it's hydrolically controlled tranny so a PCM flash or PCM from a Dodge truck with a manual tranny would work. This may be the best route.

Another wild thought. See what it would take to fit the ZJ dash into the MJ.





Of course the 5.9 dash is newer and nicer than this.

This is an awsome project. And the 5.9 is much cooler than a SBC. I've often thought about what it would take to swap in a 5.7,or 6.1, HEMI into my MJ. I'll second Kittrell's sugestion,think about swapping over the entire harness. Are you set on keeping the MJ's interior? It may may be possible to retrofit/combine clusters,etc.

I have done a 5.9L swap from a 96 Dodge Ram 2500 with a 46re and NP241dld transfer case.
First off your stock dash will not work. the ZJ dash runs on a bus system, 2 wire hookup. Your MJ will have guages that are run directly from the sensors. So plan on installing autometer guages etc...

Wiring, get the factory service manuals for BOTH vehicles. You will need the complete wiring diagrams from both in order to make the correct splices from the zj harness to the MJ harness.

You can do it yourself but it is time consuming. Not hard but you just need to check and double check everything you solder.

As for the 5.2 vs. 5.9 they are physically the same.
I did this in a tj so i had a frame to work with. not sure if anyone makes mounts for the xj. You will more than likely have to fab mounts yourself.

The 46re has 23 spline output, so if your NP231 has a 23 spline input, it will bolt up.

Another big hang up people run into is the security system. If the ZJ has the factory security the PCM will need to be reflashed to have that circuit taken out or you will need to find a pcm for a 5.9L that did not have the security system from the factory.

99% of the wiring is done at the relay box. You will also need to splice in the wiring for the MJ fuel pump.

Go to alldatadiy.com and buy the service manuals. You can not do the wiring without the schematics for both vehicles. It is well worth the cost.

Let me know if i can help in any other way.

here is a pic of my install

dakineJ said:

I've often thought about what it would take to swap in a 5.7,or 6.1, HEMI into my MJ.

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Unfortunately, this one is mostly a pipe dream. These motors with not physically fit in our engine bays.