89 MJ

Looks like a nice truck! Welcome to the forum! Check out this thread, there are quite a few original owners around here. Also, please drop your truck in the registry. https://comancheclub.com/forum/28-comanche-registry-vin-decoding/

I saw one like this except with stop, drop, and roll instead of free drugs

Just thinking out loud here, but I would think that the rear axle still should be alright at least for moderate driving. But what about a KJ rear? Yes, its spending more money, but you already have the right front end gears and the rear axle is wider, plus its an 8.25.

That 2.5L overflow is really good. I think it’s the best option for these trucks.

If you go with the SM420, I would look at running an NP205 if you can.

If you look in the wheel opening, it looks like it was red originally. Plus it has a 2.8. Hope this helps.

That interior is excellent.

I know both The Pub and Tech have this feature. Here's a screenshot from The Pub.

There is! You'd have to create a new topic with a poll.

Its only worth 12k if it doesn't need anything. If I were in your shoes, I wouldn't pay over $8500 for it. Its just an XJ, nothing special. If it were dialed in and had new tires on it, only then would would I think its worth anywhere near 12k I just jumped on Bring A Trailer for some price comps because that's where all of the high priced ones seem to sell. These ones have all sold within the last 2 months and there are plenty more examples on BAT. 44k mile 2001. Sold for $18k, but is not as clean underneath. Repainted 2001 with 59k miles. $11.5k 123k mile 2001. $8800 97k mile 2 DOOR. $15k 65k mile 2001. $14.7k I'm sorry, but there is no way that that XJ is worth 17k. Based on what I just linked, I don't even know that its really worth $12k. The prices for these are not as crazy as they were just a year or so ago.

Another thought. If it was a barn find, it will probably need a lot of work. Probably needs tires and all of the other rubber components unless they were done already.

I think he’s asking about 5k more than it’s really worth on a good day. $12k seems like about top dollar in my opinion. I also don’t think it’s really a unicorn. It’s a 4 door auto with cloth interior, just like most XJs.

They’re great engines. My parents had one in a 94 S10. I’ve driven a full-size truck with them too and it does well. Plus they’re just a small block short a couple cylinders, so parts are plentiful and V8 swaps aren’t too hard in the future.

Exactly why my brain went 4.3 as well. A Buick V6 was available in a lot of early CJ5s IIRC, so I would think that the 4.3 should fit and just be a better choice.

I would be skeptical of used gears. They are a wear item after all and if you do not get the pattern set up the same, it will likely make noise. If it were my money, I'd do a TrueTrac in the rear with new Yukon on Spicer gears. The TrueTrac is expensive, but seems to be a great option for a strong limited slip that does not wear out and is still daily drivable.

That would be us. I think Pete is right. It is probably about removing the heater core without pulling the dash. This is the thread, but it looks like the video us unavailable. Pulling the dash isn't too hard though. I tried checking Cruiser's site for the video too and could not get the site to load.

This looks like a very cool project. If I were in you shoes, I would be choosing between a Renix 2.5L and a GM 4.3L V6 with TBI for an engine. I'm looking forward to seeing updates.

I have probably 140k miles on my MJ, so a decent amount less than you. My truck has blow by. No leaks, but the engine is always just a little dirty from the blow by. In a 3,000 mile oil change, it burns a negligible amount of oil. I do get seepage around the CCV grommet, but I also have not done Cruiser's valve cover mod. Similarly, my Eagle engine has an estimated 85k miles on it by now, I went through and resealed it, but did not touch the rings or the bearings because the bearings look brand new. If you pull the PCV, the thing looks like a freight train when its up to temp. Its bad enough that it has a home made road draft tube made for it so it isn't creating puddles of oil on top of the engine. The thing drinks about a quart of oil every 150 miles and at a hot idle, you can see a cloud of oil smoke. My Eagles previous 110k mile 258 was no better. Based on that, I would say your engine is about right for the mileage. Do you have any oil consumption issues? A quart between oil changes should be about right for these engines, in my opinion. A good portion of this also depends on how well the engine was taken care of by previous owners. That said, keep oil in it and it will run forever. These engines were designed in a time when vehicles were pretty much worn out by 100k miles. At this point, anything else you're getting out of it is a bonus. I think its also worth mentioning that these engines were from an old engine family even when they were new. The AMC I6 family that the 4.0 is apart of goes back to the 60s. Other than the cylinder head design and the fuel injection, a 4.0 is an engine from the 60s when odometers only had 5 digits because most cars didn't live past that. Sure, GM did the same thing with the small block, but those engines got a ton of updates to them throughout the years, including getting roller cams and one piece rear main seals, which do a ton to modernize an engine, but the 4.0 never got such. You don't see it too much with the Jeep stuff, but in the AMC community, you see a lot of people swapping their 6s between 100 and 150k miles because they're just plain worn out. Everybody says that these engines cannot be killed, and for the most part, I agree. With that said, what those people fail to mention is that while these 4.0s will not die, you do need to treat them like an engine from the 60s if it is a vehicle you care about. And by that I mean you either need to check the oil at least once a week and expect blow by or you need to pull it out and redo it. I think its also worth saying that quality control was not as good when these trucks were new. Sure, the quality of materials were better, but even super nice original vehicles had their problems with panel fitment and paint, so I'm sure that there were plenty of mechanical issues too. This was all automakers too, not just AMC. I'm not saying this to hate on AMC because none of the other manufacturers were any better at the time. AMC did really well with what they had and did great things for the automotive industry as a whole. I'm also not trying to sound condescending here. I'm telling you this explanation the same way I had to hear it and piece it together myself. It is a very frustrating lesson to learn, or at least it was for me. It really isn't always very much fun throwing time and money at an engine that is worn out, but that's about all either of us can do right now. The light is at the end of the tunnel though and more money and hopefully more time are right around the corner.

I’ve never seen that either. In the picture, it looks reddish brownish orangish. Is it sludgy or does it seem to have chunks and grit in it? I would say that oil looks reasonable for 1300 miles on it, but with that stuff on the dipstick, I’d give it a change and go back to conventional oil.

December 2025 - Old Red: The Story of a California MJ Owned by @NickyV Build Thread- I just started a build thread -- took me way too long. I will be updating it soon, but in the meantime, here are some of my projects. NICK'S MJ PROJECTS: DIY Headlight Harness Upgrade Replacing Headlight Switch (Fixed Non-Functioning Dash Dimmer) Factory Radio Experiments & Upgrades (A Mini-Build Thread) Power Steering Pump Troubleshooting Headliner Refurbished VIDEOS: Year/Model - 1987 Base Drivetrain- Four-speed (AX4) -- All factory as far as I know. Cooling- It might be the factory radiator. I'm not sure. But I have replaced two thermostats. And the very first under-the-hood project I tackled was replacing the thrashed water pump. Electrical/Ignition- Ignition is mostly stock, although I had to replace the starter back in 2021. Suspension/Steering- All stock for the most part. I did put some new shocks in while working to cure my death wobble, but they weren't anything special. I do plan to overhaul the suspension in the next year or so to get a little bit of a lift/bring the ride height back to factory (it's definitely saggy, especially in the back). I upgraded from non-power to power steering last year. Interior- All black vinyl interior (including the floor... no carpet). Bench seat. The interior of the cab is where I've done most of the work. And there was a LOT of work to be done. My truck didn't even have a cigar lighter when I bought it! Radio & Dash Controls: Switches (Fog Lights & Camper Shell) Tech: Audio Input Switch & Wireless Charging There's a link to some pictures of my refurbished headliner up above, and I installed an aftermarket dome light in the center of the headliner. I put in footwell courtesy lights that I pulled from a junkyard XJ. I swapped out the I overhauled the sound system. My MJ came with a crappy aftermarket head unit and other jury-rigged audio tomfoolery. The PO had literally used Velcro to tuck small computer speakers up underneath the dash where the tweeters go. Here is a list of audio upgrades I've made since buying the truck: Door Speakers (cut holes in the door cards myself) New 6x9s in the pillars OEM style tweeters (Jensen Accusound pulled from a junkyard XJ) Two amplifiers, both mounted on wooden rails that I attached to the trim studs behind the bench seat. One amp runs the 6x9s, door speakers, and tweeters (door and tweeters wired in parallel). The other amp runs a single sub, positioned behind the bench in the middle. It sounds pretty good in there, if I do say so myself. I've got a factory radio that I pulled from a junkyard Cherokee. It's an AR-7750, with no cassette deck and the bass/treble faders. I have the radio and a Bluetooth receiver (hardwired) running through a two-channel RCA selector. Switch is in the dash. I'm still working on a video/writeup about that, which I will add to my build thread! But here's a little sneak peek... I used my ash tray to hide some of my stereo controls. I installed an in-line RCA volume pot to control the Bluetooth volume, and I put a remote bass controller in there as well -- along with an LED that lights up when the headlights are on. Brakes- I haven't done anything to the brakes (besides fixing a broken parking brake pedal). This is definitely high up on my list. Thankfully, since I drove it with death wobble for way too long -- and since it is a 4-speed 2.5L, I don't really ever get going all that fast. Lighting- I did the headlight harness upgrade last year (mini-build thread on that project). And I recently replaced all my turn signals and running lights with LEDs (including the reverse lights). I'm planning to try halogen first before considering going LED on the headlights. I rarely drive the truck in the snow, but if I do get caught in snow storm, I want to be able to see. I highly recommend converting your turn signals and backup lights to LED. Not only are they brighter... Switching out the two-prong turn signal relay for a three-prong LED relay greatly improved my blink rate. I think you could fix this by cleaning up certain grounds, but it was a nice bonus of the swap. Now my turn signals flash brightly and frequently and I'm a lot more confident that people know I'm planning to merge. As you may have noticed, I have a camper shell. I still have a lot of work to do on that thing... I've got grand plans! All in due time. But as of now, I have done two important upgrades. First, I wired up the third brake light. I could have gotten a kit with a special relay, but I just decided to piggy-back a long wire onto my brake pedal. Ran it through the firewall and all the way back to the third light. Works like a charm! Second, I installed a custom switch in the dash (probably where the cargo light switch would be) that allows me to turn the dome light of the camper on and off from the cab. I still need to figure out how to make it a three-way switch with a second switch in the camper. Still brainstorming the best way to do that with the least amount of wiring. Exterior- I've covered most of the exterior stuff above, in the lighting section. The only exterior modification I can think of is I replaced my window swipes with rubber ones from a 2000 XJ. I actually just picked up another pair of swipes and I'm planning to do it over. I didn't do a great job the first time around and I have better tools now. Wheel & Tires- Finally replaced my tires last year. I went with Goodyear Wrangler DuraTrac 235/75/15s. No complaints! Misc- Can't really think of anything to put here. Best MJ story- When I bought my MJ, I had no idea what I was getting myself into. I knew I wanted a truck that I could teach myself how to work on. Over the years, it's been frustrating, inspiring, scary and exciting. It's been a great experience. Some of my best MJ stories were definitely not fun in the moment. But they all involved problem solving and creative thinking. I've replaced a thermostat in a park-and-ride lot off the side of the freeway and fixed my clutch at a gas station. I learned that if your starter is going bad, you can sometimes temporarily revive it by giving it a good whack (a fellow Jeep enthusiast taught me that one when I was starting to worry that I'd have to pay for a tow out of a primitive campsite in Death Valley). I am a much more competent mechanic now than I was before the MJ. Which brings me to why Comanche Club is awesome. CC is Awesome! Why? I wouldn't have been able to accomplish nearly as much as I have without all the awesome people on Comanche Club. I deeply appreciate how nice, patient and willing to share you all have been. I started out as a lurker. Then I created an account. Now I'm posting regularly. I bet that's the same experience a lot of us have had. I hope that in the future, I can start to help others the way you all have helped me. I've had my MJ since 2019 and I have no plans to give it up any time soon. Thanks so much for asking me to be featured on MJOTM. I thought I wouldn't have much to say, because I still feel like I have so much work to do on my truck. But taking the time to fill out this form has reminded me of just how much work I've put into it... and I'm excited to keep it going! Congrats on MJOTM! I really like all of the documentation that has gone along with this truck over time. Funnily enough, its not the first red, 4 cyl MJ to be December MJOTM either in the time I have been the MJOTM caretaker.

Seems like everyone has a PO story like that lol. The thermostat is definitely a factor. Daily driving these trucks in town will kill mileage too. My truck is 14-15mpg in town and will only get 20 or so cruising on the interstate for the entire tank.

I’d verify the temp with an infrared gun, but it could be that it was swapped to a 160. Being that it was designed to have a 195* thermostat, it would get slightly better gas mileage. It might also run a little bit better. With how spotty the quality seems to be with new thermostats, if the installed one seems to be working fine, I’d stick with it. If you have any troubles with it, I’d run a 195*.

Can’t blame you there at all! I do the same after all. Glad to hear I’m not the only person on here who checks CC out instead of scrolling social media

It’s that time of year! Tree is on the roof.

Look at you living it up on a Friday night as a college student scrolling through 15 year old CC posts haha. Though I’m now doing the exact same thing as a college student too