getbent Posted January 12, 2013 Share Posted January 12, 2013 Hi new to the fourm and my 88 lwb mj. It has the 2.5l in it now but its been ran hard and the ax5 is starting to make some noise. I am wanting to swap in a 4.0l ,aw4 setup. I am wondering if you guys can give me some info and insite on what all would i half to change if i went with a motor and trans from a 97+ xj. I have been told that i would need to change the hole dash and heater setup to do it. Is there any truth to this? Any help or info would be great Thanks Ben Link to comment Share on other sites More sharing options...
Guest Posted January 12, 2013 Share Posted January 12, 2013 The short answer: Complete "bastardized" (High Output to Renix) wiring harness. Shortened driveshaft. Firewall massaging to fit the 4.0 Radiator Link to comment Share on other sites More sharing options...
Guest Posted January 12, 2013 Share Posted January 12, 2013 The short answer: Complete "bastardized" (High Output to Renix) wiring harness. Shortened driveshaft. Firewall massaging to fit the 4.0. Radiator supports for the 4.0. IIRC; there should be many topics on this if you search through the tech forums. Also, sorry for X2 post. Link to comment Share on other sites More sharing options...
getbent Posted January 12, 2013 Author Share Posted January 12, 2013 I have done some searches and none of what i find are useing the obdII system from a 97+ xj. I also read that the fire wall was changed in 87 mj and no fire wall mods are needed As far as radiator i would be using the support from the donnor and building a drive shaft is no big deal. Link to comment Share on other sites More sharing options...
Backdraft Posted January 12, 2013 Share Posted January 12, 2013 It depends. Do you want to use just the motor and transmission from the donor? Or do you want to use the control systems/wiring/sensors/OBDII from the 97+ as well? Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 12, 2013 Share Posted January 12, 2013 If your donor is s 96 plus, yes, youll need to swap EVERYTHING from the donor.... all wiring, and HVAC box assy. The Xj rear wiring will need to be modified as well to make the MJ taillights work. You know about eh radiator core support, and the driveshaft... so thats about it. Link to comment Share on other sites More sharing options...
getbent Posted January 12, 2013 Author Share Posted January 12, 2013 well i am not wanting to change all the dash and heater box stuff so it looks like i need to find a pre 97 xj then. going that way i should be able to keep the factory dash and gauges right? Link to comment Share on other sites More sharing options...
jimoshel Posted January 13, 2013 Share Posted January 13, 2013 Swap the sensors and stuff on the engine and make it a pre OBDII Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 13, 2013 Share Posted January 13, 2013 If youre changing from a 4 cyl, to an 6 cyl, youll probably need to pull the dash anyways to swap computer wiring. That and there are also differences in regular dash wiring between years as well, with different connectors and pin locations... etc. The dash isnt that hard to pull, and once its out, its nothing to swap the HVAC box seeing as how the coolant is drained already anyways for the engine swap. That will also give you a chance to clean the thing out as they get pretty dirty over the years. When I swapped mine out for adding AC, it was full of mouse house and what have you. I cleaned it all up and doused the whole thing with Lysol to make sure it was all disinfected. I also cleaned up the blower motor and lubed the bearings in it at the same time. If you can swap anconvert engines and such, pulling a dash is nothing. You can keep the same outer dash, just change the electronics underneath and update as much of that as possible with your newer donor. If you get a 96 plus, youll have OBDII, and easier diagnostics for later on. Seriously, its not that much more work to do it all the right way the first time instead of trying to match up stuff piece by piece. Let us know what you figure out! And good luck! Link to comment Share on other sites More sharing options...
jpnjim Posted January 13, 2013 Share Posted January 13, 2013 Since you are starting with a 4 cylinder MJ, you might be better off using the "BIGHEEP Method" http://comancheclub.com/topic/36506-semi-ho-swap/#entry365458 Nope, you can use the same under dash harness. You just have to repin the blukhead connector to match the MJ. I swapped a 93 XJ 4.0L into my 1988 YJ with a carbed 4.2L and I used the same under dash harness. You can actually swap in the new engine, hook up the fuel and get it to run by just splicing in 5 wires. ^^I haven't done a harness match up swap like BIGHEEP did, so he'd be the best to ask, but would assume the way to start would be with a 91-95 engine (easiest to swap) & under hood harness/computer. Seems like you could get it to work without the HO gauges, but I'd also want to grab the 91-95 XJ gauges & a 91-92 MJ fuel tank sending unit (otherwise your gas gauge will read backwards) Link to comment Share on other sites More sharing options...
Bounty Hunter Posted January 14, 2013 Share Posted January 14, 2013 Words to live by: Link to comment Share on other sites More sharing options...
getbent Posted January 18, 2013 Author Share Posted January 18, 2013 ok thanks for the info on this so far. the repinning of the harnes shouldnt be a big deal as long as i can find the pin outs for both (Its what i did to put the mpi on my cj) the other thing is finding a donner in my area that i can afford. does anyone know what all problems would i run in to using a zj as a donner? Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 20, 2013 Share Posted January 20, 2013 You wouldnt have all necessary parts if you use a ZJ as a doner. The reason you find an XJ is so you can get the radiator, the core support, and all the correct placed and length wiring. That and youll have a bunch of other spare parts and possible upgrades as well. Most XJs had power windows and locks, so that might be another possible upgrade for your MJ on top of getting the drivetrain. And the 97 up models had one peice door windows and better mirrors. This is something you could do in a weekend after getting all the other stuff done, and if you do the whole dash and dash wiring, it would be plug and play! If you want a NP242 transfer case too, youll need all the shift linkage from the donor as well. Full time 4x4 would be a nice upgrade and a reselling point if it ever comes to it. A whole XJ is just a better option for doing this, theres no other way around it. Why waste all time repinning harnesses when you could just swap it in complete and be done and ready to go? Just sayin. It would save you a ton of headaches later on doing it this way. Link to comment Share on other sites More sharing options...
getbent Posted May 14, 2013 Author Share Posted May 14, 2013 ok so I am moving forward on this and have picked up a 98 Xj. there are a few questions that I have before I start pulling parts and one is the fuel pump/sending unit. I seen somewhere on here that I can cut a hole in my gas tank to drop in the 98 pump using some ring but can't seem to find the ring anywhere. the other is my mj has crank windows and I am not sure if I can use them with the new dash any info o these would be great. Thanks Link to comment Share on other sites More sharing options...
ComancheJon Posted May 14, 2013 Share Posted May 14, 2013 Here's a tip from a fairly new comanche owner/comancheclub member: Head over to the "Your Project MJs" section and read a few of those builds thoroughly. We will always assist you if needed, but a lot of those threads will give you a lot of knowledge and a majority of them contain an engine swap of some sort. Link to comment Share on other sites More sharing options...
87Warrior Posted May 14, 2013 Share Posted May 14, 2013 Don't start pulling stuff apart yet. You will get in over your head with the 97+ swap. READ THIS FIRST: http://comancheclub.com/topic/30671-97-swap-how-to/ Now, how can we help you? Link to comment Share on other sites More sharing options...
getbent Posted May 14, 2013 Author Share Posted May 14, 2013 I have read that and in there it has the pic of the ring but it does not say where he got it or if he made it Link to comment Share on other sites More sharing options...
Backdraft Posted May 14, 2013 Share Posted May 14, 2013 The ring I bought. However, I never liked the way it all worked. I could only use about 3/4 of my gas tank because the pickup for the fuel pump doesn't reach the bottom. What I did was replace it with a Dakota 22 gallon tank and pump/sender assembly. The fuel gauge reads more accurately, reaches the bottom of the tank, and gives increased capacity. There are a few threads floating around here on the subject. I also have some highlights in my build thread I think. Link to comment Share on other sites More sharing options...
getbent Posted May 15, 2013 Author Share Posted May 15, 2013 ok so I need to find a 97+ Dakota tank, pump/sending unit and ill be good to go. so does anyone have any info on the doors? Link to comment Share on other sites More sharing options...
getbent Posted May 19, 2013 Author Share Posted May 19, 2013 I my have overlooked this in the builds that I have read but do I need to use the gas pedal from my donor or the one that was in my truck? Link to comment Share on other sites More sharing options...
getbent Posted May 22, 2013 Author Share Posted May 22, 2013 ok so motor mounts? it looks like there is two sets of holes on the frame that they can be bolted to but do I need to move them or not in the link that 87warrior put up there is a pic that shows the mounts and mine look to be in the same spot. but I am not sure if that is right or not. any info on this guys? Link to comment Share on other sites More sharing options...
Jongat88 Posted May 30, 2020 Share Posted May 30, 2020 I am doing the swap I have a 89 mj with a 2.5 and a manual trans. I already have the doner vehicle 95 xj sport with a 4.0 ho and a automatic trans. I am deep in this project already. I got the motor and trans pulled from doner and the motor harness , dash and plan on keep going after reading yalls forums. Any thing else I should know about this swap like anything tricky about these years, or models ? Link to comment Share on other sites More sharing options...
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