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Unread 07-31-2010, 08:42 PM   #1
saylorjerry
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TJ 2.5 to 4.0 swap question...

I've read a bit into what a swap would involve, and in my hunt for parts I ran into a question. If 89 and later XJ's used a 4.0 with a AX5 and NP231, what is the issue with putting a 4.0 in front of my TJ's AX5 and NP231? Thanks in advance for any input.

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Unread 07-31-2010, 08:53 PM   #2
moonshinefuel
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Ax5's don't go behind 4.0's.
Its a lot of work you are talking about, you will need a new transmission too. Many opt for a V-8 conversion as you will need to replace the wiring harness as well, and weld in new motor mounts. Again an ax5 is a no-go behind a 4.0.
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Unread 07-31-2010, 09:07 PM   #3
Ron98jeep
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so i would be better off replacing the 2.5 & not attempting
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Unread 07-31-2010, 09:17 PM   #4
Ron98jeep
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being a previous ford owner, what would it take to install a 300 six cylinder into a wrangler? I've never had a problem with that motor & i would think it would be a powerhouse in a wrangler
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Unread 07-31-2010, 09:27 PM   #5
Ron98jeep
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1998 engine swap 2.5 without A/C to 1995 4.0 with A/C

any assistance appreciated
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Unread 07-31-2010, 10:51 PM   #6
Ethan79
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Quote:
Originally Posted by Ron98jeep View Post
any assistance appreciated
obviousl motor mounts/wiring/ecu/tranny... but this would be a goooooood swap. those motors are amazing. they just go and go and go
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Unread 07-31-2010, 11:04 PM   #7
RogueSpear2023
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The problem with the 300 is it has way less HP and torque than the 4.0L I6 has, and it would require the same amount of work a 4.0L and the 4.0L will probably last longer. I would say the best bet if you want to do a motor swap is to do a V8 it's the same amount of work as the 4.0L, ReMoVeR on JF did the 4.0L swap ask him, he says every time this comes up, he wishes he would have done a V8 way more power, and it's the same amount of work. Also the AX5 will not take the power of a the I6, in the cherokees the AX5 was behind a the 2.8L V6 which was a real pooch power and torque wise. So it was never behind the 4.0L, why because it wouldn't last long. All 89+ Cherokees with the 4.0L use the AX15, not sure where you get the info that the AX5 was behind the 4.0L.

Whats involved in the swap
New Engine/transmission 4.0L/AX15, or V8/many options
New motor and transmission mounts
New Radiator
New wiring harness
Also will have to change the input shaft on the t-case.
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Unread 08-01-2010, 07:11 AM   #8
Shrek
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I did the 2.5 to 4.0 swap. I had a low mile 4.0 donor for free or I would not have done it! Computer, wiring, motor mounts etc. Hell, even the steering shaft mount is different on the 4.0. I wouldn't attempt it unless you're a welder and monster garage type mechanic. To completely rebuild the 4cyl is($1400). Put a V8 in it. No matter what you do, the AX5 is worthless behind anything other than the 2.5.
Having said all that, the 4.0 is a superior TRAIL engine over the V8. Most V8s won't give you the torque at 600-1000 rpm like the 4.0 when your crawling around. On the street or in the mud the V8 would be a panic but for a trail Jeep, the 4.0 is pretty hard to beat.
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Unread 08-01-2010, 09:16 AM   #9
saylorjerry
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Thanks for the clearup and input guys. There must have been a typo in the XJ section on here. Unless I read it wrong. I wsa looking into a V8 because for the dollars I heard it was a better swap, but I really don't need all that power for the running I do. Really the 2.5 does the job, I'd just like to be able to go 70 on the freeway without having to have the wind at my back. I also am not a huge fan of cramming a smallblock into the engine compartment. I've got rather large meathooks and like to have some room to play. Again thanks for the input.
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Unread 08-01-2010, 09:22 AM   #10
saylorjerry
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yep...that was my bad, I looked at one and noted the other... it is the AX15 in the XJ
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Unread 08-01-2010, 09:55 AM   #11
gensysmike
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I had a shop do my 2.5 to 4.0 upgrade. They did not have to put a new wire harness in. They sent the 4.0 wire harness out for modification to mate to the 2.5. They claim it is better than putting in a new wire harness. It works fine. No issues on my end. If you are interested let me know and I will find out and pass along the details.
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Unread 08-01-2010, 04:14 PM   #12
saylorjerry
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how much did the shop charge for the swap? I'm definately interested.
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Unread 08-01-2010, 07:49 PM   #13
JeepN95YJ
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LOL @ V8 as easy as 4.0.

I've swapped both. Love the 2.5 to 4.0 swap. Very easy and inexpensive if you shop around. My swap: http://4bangerjp.com/forums/index.php/topic,8673.0.html

The 4.0 doesn't require a modified harness in any way. Simply unplug the 2.5 engine harness from the firewall and computer and plug in the 4.0 harness.
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Unread 08-01-2010, 07:56 PM   #14
JeepN95YJ
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Quote:
Originally Posted by Shrek View Post
Computer, wiring, motor mounts etc. Hell, even the steering shaft mount is different on the 4.0. I wouldn't attempt it unless you're a welder and monster garage type mechanic.
I cut and reused the 2.5 motor mounts. The only difference in wiring was the engine harness but it is plug and play. No modification required. Same with computer. The steering shaft didn't need to be touched except to unbolt it while I welded on the frame side motor mount.

I'd hardly call myself a monster garage mechanic. What specific problems did you have with the swap? Did you use a TJ 4.0 and harness?
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Unread 08-01-2010, 08:08 PM   #15
davidchancey
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I've also done the swap. Very easy swap I thought. It's alot easier if you use the same year parts. Was also cheaper than regearing. Got the whole swap done for $200 including price of motor.
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