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swapping a 2.5 for a 4.0

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Old Mar 10, 2009 | 09:45 PM
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Default swapping a 2.5 for a 4.0

I have a 99 cherokee with the 2.5 weiner and i was wondering if i could put the 4.0 in it. Sorry if this is a stupid question. haha.
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Old Mar 10, 2009 | 09:48 PM
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easier to just sell it and by one with a 4.0 in it.
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Old Mar 10, 2009 | 09:57 PM
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Originally Posted by c-loss
easier to just sell it and by one with a 4.0 in it.
yea, i would but i love this jeep and there's a 4.0 in my grasp with a tranny. they were both remanufactured.
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Old Mar 10, 2009 | 09:59 PM
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and plus you have the 4.10 gearing so if u swap your motor yo will be set for larger tires
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Old Mar 10, 2009 | 10:01 PM
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So does anyone know if it's actually possible? Would I have to do some cutting or any hot work? Or would it just fit right in there?
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Old Mar 10, 2009 | 10:09 PM
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Well not 100 percent sure on this but I believe the computers and wiring are different. The mounts will be different so there's some fabrication involved to make it fit. Then there's the cooling system to upgrade and then the rear end and so on. It's doable (but almost everything is) but I have never seen it and I would consider it impractical given the cost vs. just buying a 4.0. My change here only, your opinions may differ...
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Old Mar 10, 2009 | 10:16 PM
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what is the reason for the 4.0 over 2.5
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Old Mar 10, 2009 | 10:25 PM
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the computers and wiring are different. The mounts will be different so there's some fabrication involved to make it fit. Then there's the cooling system to upgrade
All true. My buddie Tried and gave up there was just tooo much to change and just parted the rest of the 2.5 heep and bought another 4.0 and had spare parts. Its quite an undertaking I wish you luck. Make sure you take pics and document it so you can help other people. I'm sure there are lots in your same boat , and again good luck but most of all have fun!!!
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Old Mar 10, 2009 | 10:32 PM
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Default 2.5 to 4.0 Jeep MJ

I have a 95 XJ with typical rust problems has a good 4.0 5spd 231 transfer case. And I just got a 87 MJ that is rust free but has blown 2.5 with 4spd with 4:10s. If I swap wiring computer and such will the whole drive train fit?
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Old Mar 10, 2009 | 10:44 PM
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thanks for all the input fellas. I may reconsider after hearing what i've heard. haha.
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Old Mar 10, 2009 | 10:46 PM
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Another thing, if i remember right the fire wall was actually shaped differently for the different engines. I could be wrong on this but i remember hearing it somewhere.
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Old Mar 10, 2009 | 10:47 PM
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Originally Posted by xer0
what is the reason for the 4.0 over 2.5

just to have a little more gusto.
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Old Mar 11, 2009 | 07:07 AM
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Basically you will need the wiring harness from the firewall forward, and the computer and ALL brackets, and associated parts from the 4.0 donor. This includes the frame horns. You MIGHT also need the x-member and t-case shift linkage.

A buddy of mine did this with his MJ... all his parts came from my garage, or the PNP. It took him about 2 months if you do a search on Comancheclub.com you will find the info in the project section.
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Old Mar 11, 2009 | 11:36 AM
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I like my weiner so far. I mean my 2.5.
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Old Mar 11, 2009 | 12:35 PM
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Originally Posted by PingPong
Basically you will need the wiring harness from the firewall forward, and the computer and ALL brackets, and associated parts from the 4.0 donor. This includes the frame horns. You MIGHT also need the x-member and t-case shift linkage.

A buddy of mine did this with his MJ... all his parts came from my garage, or the PNP. It took him about 2 months if you do a search on Comancheclub.com you will find the info in the project section.
yeah, it does seem like quite the long headache porject.
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