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2.8 to 4.0


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ok so i have a 4.0 from an 87 cherokee with a tranny and transfer case. i would like to know how hard would i be to swap that in place of my 2.8? has anyone done it? is it worth it? i know its going to take a BFH but what if i took the fire wall out of the cherokee and put it in place of my fire wall? questions concerns ideas??

 

 

N.O.T.G.

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Depending on how late in the year your MJ was made it might be able to fit the 4.0L just fine. The bodies got changed ahead of time while the 4.0L was still in R&D getting ready for the next year. If this is the case you're in business, it not then it will take quite a bit of work but I'll let someone who might know more go into detail. I was going to do this with my old '86 till I heard what all it took and just took the easy route and bought a new MJ. :D

 

~Alex

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Replacing the firewall would be... a lot more trouble than a couple swings of a hammer. They're not quite that different.

 

You'll need more than the motor, trans, and T-case. You need EVERYTHING under the hood and dash. All the wiring, cooling, brackets, RAD support and the stuff behind the header panel.

 

You literally have to move most of the guts over from the donor.

 

Another thing you'd need to take into consideration is gearing. Plus you'll have to have a read driveshaft made if you can't find one.

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Very doable. Plenty of people have done it. Just takes a lot of time. This isn't a quick one-weekend deal unless you've done it before.

 

What gearing do you have in your MJ now?

What gearing is the donor?

 

I would worry about the axles last.

 

I would strip the MJ clean, get literally everything out of it. This will give you a good opportunity to clean up any rust spots, and maybe re-paint the engine bay and inside of the cab.

 

Then I'd pull the motor and trans out of the donor. Move all the wiring and such into the MJ, then dump the motor and trans back in. I'd give the motor and trans a good look-over, probably throw a gasket set on it at least while it's out.

 

It's just as involved as going from a 2.5 to a 4.0.

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well I'm like 75% positive that my mj has a d35 but it doesnt a tag so I'm not sure. I'm going to puta new gasket on both diffs pretty soon so when i do that i will count the gears. are there any tricks to making it any easier or is it just dive in and plow through?? Thank you for all of the help guys.

 

 

N.O.T.G.

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Take lots and lots of pictures. It is not overkill to snap a shot of each item as you unbolt it. It costs nothing to take digi pictures so snap away. Keeping everything organized and orderly is the key. I set up an excel spreadsheet when building my 88 and it was a great help (though admittedly my project was not as straightforward as yours).

Random thoughts:

-completely gut the MJ first, then you can install parts as you remove them from the Cherokee. Formulate a plan of attack, as I'm sure some parts need to be installed after others.

-Remember that the 2.8 has a mechanical fuel pump and so you'll still need some parts from another MJ.

-You'll need to swap over the 4.0 radiator and that means the radiator brackets, hood latches and hood.

-Jack up one rear tire on your truck, put the truck in neutral and rotate the tire around twice (to simulate both tires turning once). While you do that, count the number of times the driveshaft rotates (mark it is you want). that will give you your gear ratio. Chances are that the MJ will have better gearing than the XJ (but there's no guarantee).

 

 

 

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so i was driving last night and when i got back to my shop my truck took a big old dump on me. white smoke came pouring out frome everywhere and it had started to knock real bad. and i was so defeated that I'm thinking about just selling it and getting rid of all of my problems. but then the other half of me has always wanted a comanche and makes me want to keep it. i have come to the conclusion that i bought the worst type of comanche (2.8 2wd) because the only drop in swaps are another 2.8 and a 3.4. What should i do guys?

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I would say, sell the truck, and find a 4.0L... They aren't rare by any means, just keep a keen eye to craigslist. That way you can have a solid project to start from.

 

Just me, but thats the way i'd go with it. Ship it, buy a new one.

Rob L.

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Now the the engine is junk in this one, its not going to be worth anything selling it. Find a good 3.4 and swap it in and head down the road! car-part.com will help you find what you need and then you can just swap everything over and be on the road again with a much better engine and more power to boot. I saw an Edelbrock intake with a 600cfm holley 4 barrel with aircleaner for like $250 on craigslist the other day. Thought that would be neat on a 3.4 conversion, but I'm not in the market for anything like that. Get the 3.4, swap everything over from the 2.8 and go!

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I'd look for a cheap 3.4L since its a direct swap and has nice power compared to the 2.8L, more options out there for it too to up the output. If all else fails though do like I did, find a 4.0L MJ and just sell this one AS IS. The 4.0Ls are easy to find, and you might get lucky and get a really nice one as well to boot. :cheers:

 

~Alex

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So i have decided to swap a 350 in it. A buddy of mine is going to sell me one cheap. i remember seeing a write up some where i just don't know if it was on here. oh well ill take lots of pics. but I'm on the look out for another mj so we will see where it goes....

 

 

 

 

 

N.O.T.G.

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Acquiring a 350 engine is the easy part of that swap. But if you can do it right, you'll have one ginormous smile on your face. :D

Be prepared to kiss your entire drivetrain goodbye and then wage a never-ending war to cool that beast. :thumbsup:

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