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I haven't started a build thread here yet, but I figured now is as good a time as any.  My MJ started its life out as typical base model Comanche Custom with the 2.5L TBI, AX4, NP207.  It is now undergoing some major surgery as I am taking on the infamous 4.0L swap.  When it's all said and done, it will have a Renix 4.0 from a '90 XJ, an external slaved AX15 from a '96 XJ and either a NP231 or NP242.  I have a build thread over on CherokeeForum ('86 Comanche DD) and I will continue to update it there, but as of right now, this thread will start where that one left off.  Also, to aid fellow members here in potential swaps of similar nature, here's my photobucket album: Comanche.

 

More in the next post...

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A little progress the past couple of days. The engine and drivetrain is pretty much ready to be yanked out. Spent a couple hours tonight modifying the front to accommodate the 4.0 radiator. Started with a Sharpie marker and a tape measure, and ended up with a lot of cut off scrap metal and a place to put the radiator. Only thing left to do for this part is to mock up and weld/bolt on some brackets at the bottom to hold the radiator in place. Once I get the engine out, I'm going to see what kind of modifications I need to do to the firewall (hoping I luck out there but we'll see).










Earlier in the day, I busted out the Super Clean and engine degreaser, and cleaned up the bellhousing and flywheel real good. Now they're mostly clean.



Next thing to clean thoroughly is the transmission... She's not bad, but I want it to shine.

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Got the engine and drivetrain out today and did a little cleaning in the engine bay. Super Clean (in the big purple bottle) is my newest all time favorite degreaser. It cleaned all the grease, oil and crude (and some paint) off of the axle and steering components. Ripping out the engine was a breeze. I had everything unhooked and disconnected from previous nights, so all I had to do today was remove the crossmember and pull the bolts out in the motor mounts and viola! Did it all by myself within 45 minutes. Now the real work begins...






 

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Believe me, I was almost about to buy a '96 XJ with 4.0 and AX15 for $700, but the guy sold it before I could get there.  He had the interior stripped minus the dash.  Would have made a great donor.

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Made some more progress the past few days, most of which was made tonight. I tackled the dash and HVAC system (in my case, just HV lol). Dash removal was pretty straight forward actually. This write-up helped a lot: Dash removal - Jeep Cherokee Forum. I also opted to remove my steering column/wheel. I'm going to clean up the firewall a tad from where the MJ had a leaking clutch master cylinder at one point. Removing the steering column helps. I also pulled out all the internal wiring harnesses minus the two plugs that go to the B-pillar dome lights, fuel sender and tail lights. Next course of action is seeing whether or not I can get that donor XJ to fire up. Last time I know, it would turn over but failed to start. Think the fuel pump may be shot but we'll know soon. Anyway, the other bit I got done was welding in some bottom radiator supports that I cut out of some 3/16" steel plate. Overkill, I know, but its the only flat steel I had around. But enough of that, it's picture time!







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Nice project, I have a similar one in progress. As for an HO engine, I'd have no interest, if only due to the fact that the engine's torque peak was reset to be at the horsepower peak, or around 4k rpm. Personally I have no interest in top end power, since these aren't racecars. I'm much more into the low-down power. Just personal preference.

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Yea, I have a Renix remanned engine available to me, which is why I'm using that.  If I had an HO, I would've used that.  The work needed to make all this work is pretty much the same.  Like you, I'm not so much interested in top end power.  This is going to turn into my DD whenever everything is said and done.  My XJ is getting about 250 miles out of a tank, so I'm trying to make this MJ something with good power and acceptable MPG.

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I'm also installing a 4.0 into my '86 comanche, the little bits are killing me. The whole drivetrain is in, had to cut a square out of the firewall, custom driveshaft, custom transmission crossmember/mount. I'm glad you posted the pictures of the trimming and mounts for the radiator since that is my next major step. Let me know what you decide to do about fuel lines and the rear proportioning valve. I'll keep my eye on this build, good luck!

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Awesome!  Do you have any pictures and details on how and what you did to get the tranny mount and firewall modified?

 

The rear prop valve was removed when I did my WJ booster/MC upgrade.  Haven't even gotten a chance to really test out the new braking system since I started the tear down right after install of the booster.

 

But yea, any pictures you'd be willing to share would be fantastic. :bowdown:

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I'm gonna try and do some work on it today, so I'll get some pictures of the hole I cut and extension we made on the crossmember. I was also thinking about doing the WJ booster/MC upgrade, I have a 8.8 rear so the prop valve isn't connected to the axle anyway. I'm new to brakes, so if you got some pictures of what you actually ran and where to, that'd be great!

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Today, I gave the firewall a heavy dose of the BFH of Thor. I beat on that thing for 30+ minutes. Wire wheeled it and bed lined it. I think I knocked it back in the correct area to fit the 4.0, judging by pictures on the interwebz and loose measurements anyway. If it's not right, then I'll just go with my original plan of cutting and rewelding. Phase 2 will begin as soon as I get my donor XJ from my parent's house to mine. I am also planning on picking up a NP242 transfercase on Thursday from a '92 XJ to mate to my AX-15.





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Little overkill on the firewall...and it still needs a bit more I think.

edit, some pics to illustrate my thinking

86, unmodified firewall. clearance issue highlighted

 

Post 86 firewall, difference circled

 

your firewall, to me anyway, looks like it needs to be pushed back more against the pinch seam, towards the pass. side. Maybe just camera angle or something, but just what I'm getting from it all

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This is how I fix the firewall problems, and I don't do the HO swap for the extra horsepower (even though it's nice) I do it for the simplicity of the wiring and diagnosing future problems. Nothing worse than the 4000 fuseable links in a renix wiring harness.

 

 

 

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Little overkill on the firewall...and it still needs a bit more I think.

edit, some pics to illustrate my thinking

86, unmodified firewall. clearance issue highlighted

 

 

Post 86 firewall, difference circled

 

 

your firewall, to me anyway, looks like it needs to be pushed back more against the pinch seam, towards the pass. side. Maybe just camera angle or something, but just what I'm getting from it all

 

I was thinking that too.  It started to fold where you see that crooked diagonal seam that formed, putting it in a bind of sorts.  I'll have to bust out the maul or scrap that idea and do what jonb8 did above.  Thank you for the additional pictures mpace6a!

 

 

 

This is how I fix the firewall problems, and I don't do the HO swap for the extra horsepower (even though it's nice) I do it for the simplicity of the wiring and diagnosing future problems. Nothing worse than the 4000 fuseable links in a renix wiring harness.

 

Thank for the pictures jonb8.  Did you weld that new section in or is it screwed/riveted?  I ask because I notice a lot of holes are drilled around the edge, but it looks like you've got it clamped into place where you might be getting ready to weld it.

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No problem. Personally I'd cut and weld it in. Looks more professional, you know that the clearance issues will be fixed, and it looks good. But then again I get overkill with making stuff look right.

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tac weld, tack weld, tack weld. Just tack, then overlap it with another tack, then overlap it with another tack, etc. Good way to practice with a wire-feed welder, assuming you're using multi-position wire. Granted, this will more than double the time spent welding, but if you're not sure on how well you can run a bead, just tack, tack tack.

'

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I can say with confidence that Phase II of "4.0L into an '86 MJ" is a go. 46.gif

I spent the past couple of days diagnosing the no start condition on my donor XJ. Two things were wrong. First was the fuel pump was toast. Applying power did nothing more than make it hum as it was stuck and unable to turn. Pulled another pump assembly from a parts XJ I just happen to have laying around... whistling2.gif Anyway, put that into a tub of gas and went to go start the old girl after about 3 years of sitting and... nothing. So, I moved on to the next likely culprit, the CPS. As per cruiser54's helpful tips and tricks guide, I tested it for AC signal and it failed miserably. 0.2 VAC was all it would generate, definitely a no start condition. So I swapped in one that I knew worked and viola, the beast lives! Stupid me had a "ruh-roh" moment... forgot to hook the transmission fluid lines back to the radiator and, well... pumped all the transmission fluid all over the radiator and engine... eek.gif Oh, and all over me... But anyway. So now I can move on to ripping that sucker out and getting it mated with the rest of the drivetrain and my MJ.

Oh, I also got most of the final aspects of the radiator top support and hood latches done. Welded some nuts to the rails so I can bolt down the top support. Also spent an hour or so and wore out 5-6 drill bits getting those seized CPS bolts out of my bellhousing. Ended up drill all the way through the bolts. I'll have to tap them, but at least its out. W00T! Anyway, once I get the drivetrain mated, I can see where I'll need to place the tranny crossmember at. Everything else will just be wiring and dash swap stuff. Maybe I'll be done with it all by the end of the year. :crossfingers:





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Got some of the piddly little junk done on the MJ in the recent days, mainly with finalizing the hood latches and so on. Welded in a small strip of metal to give the bottom of the passenger side hood striker something to bolt to since it was just hanging in the headlight opening. The driver side one is on the edge of the headlight opening, but seems to be sturdy, so I may just leave it as is. Also pulled the hood from my donor XJ and got it mounted. Wanted to make sure that everything lines up correctly. Test fitted the front clip and it lines up beautifully as well. beerchug.gif





Also pulled the dash from my parts XJ as it is not cracked like my former dash... only thing is, it's gray and the rest of the interior is tan. So, either I'm going to spray the dash tan or change all the interior to gray, which I can do mostly with XJ trim.

Lastly, I got the drivetrain buttoned together. Went to Lowes to get some new nuts for the transfercase bolt studs. In case anyone is wondering, they're 3/8"-24. I also removed the original ignition cylinder from the steering column as I will be putting it into my donor XJ's column. I wanted to use it because I have the original keys (Jeep AMC logo branded) and that to me is pure awesomeness.




Anyway, I am trying to sell the former engine and drivetrain as it is still fully functional. If I can get that sold, I'll buy the various parts needed to finish this swap (clutch kit, external slave, 4.0 fuel pump, etc...).

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