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Interesting. Guess the AX15 isn't stock. I'm sure it's an AX15 though. Either way I'm not going to run the AW4 and still want to know what to do with the TCM wiring.

Hi. This might be more a question to post on Naxja but we all know how much better answers are here.. I'm doing a 97+ swap on my 88 mj the xj is a 98 with aw4, the mj had a stock 4.0 and ax15. I'm keeping the ax15. My question is do I need to do anything with the aw4 wiring or TCM? If I'm understanding correctly, the ECU and the TCM work independently from each other, so if I leave the TCM out will I have any trouble on the engine side? Thanks

Hey y'all I'm struggling to diagnose a no start when it's "cold". My MJ runs great (thanks cruiser54!) and starts fine unless it's been sitting in the cold overnight. When it fails to start it cranks strong but won't fire. Then I drive my XJ to work and once I get home I go to troubleshoot the MJ and it starts up first try. 88 MJ 4.0 ax15 mp231 stock renix everything with a 98 block and head. Any ideas? Oh and I can hear the fuel pump prime when it doesn't start..

Got my bushing yesterday and. It looks to be exactly the right size! Finally going to get the motor in today. Lots of debate about bearings vs bushings but my choice was made by what was available. That said, I have zero experience with oilite bushings! Before I put it in, any of you guys got any tips for me? From what I’ve read you soak it in warm mineral oil for 15min or so then cool sae 30.. can I just use synthetic 10w30? thanks again for all the help

Just ordered a bushing from Novak!! Looks to be EXACTLY the size I'm looking for! They don't have a needle bearing but recommend a bushing over a bearing anyway. Thank you BeatCJ for the link! I'm pretty sure you've solved my whole dilema!

Interesting.. Sounds like that could work. I'll ask the machine shop if they can do that

Wow, lots of good input since I checked this last! Thanks guys! I'll see if I can cover all this in one post I've got a brass bushing ordered that should be here by Monday. I don't like the idea of using a bushing much though and while I wait I'm researching other options and continuing to look for a pilot bearing that will fit. Thanks for the AX15 info I will look onto that! If I have to band-aid it now and pull the trans out in the future that's what I'll do! Couldn't agree more! When I started this project I had a lot more time! I figured I could easily do the engine swap in a weekend or two. I've had my replacement engine ready to go in for almost three weeks now with just a pilot bearing holding me up! I have to admit I don't know a lot about transmission stuff so I'm taking this opportunity to learn as much as I can. I will look into an external slave swap for sure! Hadn't thought of that! The bushing I ordered is right next to the machine shop I use. I'll ask them on Monday if that's something they can do! Not sure I understand this idea.. Do you mean drill out the crank to the O.D. of the older bearing? I also don't know what an expansion arbor is! I'll google it! thanks for the Novak link I'll get on that asap! I do have access to a car hauler and I'm looking into some backup plans in case I can't get this thing together before I move. I'm in Redmond now and moving to Bend. I'll be living in a studio with no garage for awhile but I do have friends in the area who might be willing to let me wrench in their shops if need be..

Thanks for the link.. unfortunately I don't think any of those will work. 1.055" outer diameter will fit the old engine but the newer style has to be 1.000" It's a small difference but it's the reason the bearing on the left is my above picture is all mangled. I think this is the real solution and if you can point me to those instructions I'd appreciate it! I do my best to do good work and I appreciate a real solution even if it is a lot more involved.. That said I might still have to band-aid the problem for now. When I said I'm running out of time I mean that I sold my house and we close on the 11th! One way or another I gotta get my MJ out of the garage soon!

That's exactly what I'm hoping for. I haven't measured the input shaft but the bearing I.D. is 1/2" and the O.D. needs to be 1". with such round numbers you'd think it would be easy to find. Apparently it's not. After spending some time at Napa going through "the old national bearing book" with no success I went to a local industrial supplier who also couldn't find a bearing with those dimensions... So, I ordered a bushing with a I.D. of 1/2" and a O.D. of 3/4".. I have a bearing to fit the new AX15 input shaft (3/4") I'm not sure if it's going to work but I'm running out of time so the plan is to give the bushing and 3/4" bearing a try.. If that doesn't work I'll have to rebuild the trans with a new input shaft.. Here's hoping it works out to be less sketchy than it sounds. I'll know on Monday when the bushing arrives

Yup I'm pretty sure that's exactly what I've got; earlier AX15 with a 1/2'' tip. No work today so I'm off to Napa with both my half wrong bearings and a set of calipers. Crossing my fingers I can find something that works.

I believe it’s an internal slave. I have to admit I’m pretty new to the manual transmission game. Just never had problems with clutch or trans in the past.. As for the condition I think it’s pretty good but I’ve only put about 1000 miles on this mj. Other than replacing a leaky master I haven’t had any problems. The tranny and transfer case look real fresh and clean like they were rebuilt recently. The history of this mj is a little mysterious. It’s only had 6k miles put on it since 2007 with great records kept till 2014 then nothing but almost no miles on the clock till I bought (rescued) it. Somewhere in between the trans and t case were refreshed and barely driven..

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I guess I should give a little more background on what I’m doing.. I’ve got a stock 88 mj 4.0 AX15 (pretty sure now) np231 d44. Had low compression in cyl 4. I had a spare motor for my 98 xj (AW4 np231 8.25) I decided it was easier to just swap in my spare than rebuild the original. I’m keeping the original tranny transfer case Renix stuff etc. I’m following cruiser54’s “HO swap into Renix” pretty much exactly. I pulled the bearing on the left from the original 4.0 in the mj. The inner diameter is correct But (after some pounding) I realized the outer diameter is bigger than the output shaft on the 98 4.0 I’m swapping in. So I hastily bought the bearing on the right which is for a 98xj. The outer diameter is correct for the 98 4.0 I’m swapping in but obviously the inner diameter is way too big. In in short I need a bearing with the inner diameter (1/2”) on the left and an outer diameter (?) of the bearing on the right. I’m just having a hard time knowing what to search for..

Thanks! I kept doing research after posting and I think I must have the AX15! The previous owner’s records said AX5 and I should’ve known better. It wouldn’t make sense to have a AX5 with a 4.0 and a Dana 44.. So I guess what I’m looking for is the 1/2 inch (older style AX15 tip) with the newer 4.0 outer diameter. I ordered another bearing today (that I now think might still be wrong) the parts guy said was for an 82 cj with an inner diameter of 5/8”. Ill look into the 74 CJ5 but if that’s a match for the newer AX15 it’ll be a 3/4 inner dia. Instead of the 1/2” that I’ll need..

Hi. I'm swapping a 4.0 from a 98 xj into my 88 mj which has an ax5 trans. I've hit a wall finding the correct pilot bearing. To my knowledge the ax5 was not an option in a 98xj and the ax15 has a different size input shaft. The bearing from the 88 mj has a slightly larger outer diameter at the output shaft of the 4.0 so searching for that doesn't work either.. Anyone run into this or know specific bearing dimensions to search for? Thanks 88mj 4.0 ax5 np231 d44 98xj 4.0 aw4 np231 8.25

I just finished moving my fuse box. Kinda. My mj sat for a long time before I got it with brake fluid from the master cylinder leaking all over the fuse box so the terminals and about six inches of the wire leading up to them were badly corroded. I ended up making my own fuse box and relocated it to above the drivers foot well. Keeping the factory box would have been easier, just a matter of extending each wire. Any specific info you’re looking for?