First of all, sorry if this is in the wrong section. I'm looking to swap from a 2.5 auto to a 4.0 manual or auto. I dont want people saying "the 4.0 swap isnt worth the effort". I just want something that can handle 33s and reliable for a daily and I have a lot of experience with 4.0s. Now that thats out of the way, I found a 2002 TJ that was in a wreck but still runs and drives with a 4.0 manual for around $1500 and i have a 1997 TJ. I'm new to TJs so how difficult would it be to swap everything including the computer to my TJ? The doner TJ has lot of other parts that I could use on mine too so I think it's a fair price as long as it's not too hard to do the swap. Thanks
2.5 to 4.0 swap
- Thread starter Djbtraxxas
- Start date
It's not worth the effort, you're right 
But, if you insist on doing it, the easiest way to do this (hands down) is by having the entire donor vehicle with you so that you have easy access to everything you need (and there will be lots of things, since it's all different.
None of your parts will work with the 4.0, not even the radiator.
You'll also have to cut and weld the engine mounts, as the frame for the 4 cylinder has different engine mounts than the 4.0. So you'll need welding skills or access to someone who has welding skills.
Keep in mind you'll also need the transmission from the 4.0, as whatever transmission is in your 2.5 will not work.
But, if you insist on doing it, the easiest way to do this (hands down) is by having the entire donor vehicle with you so that you have easy access to everything you need (and there will be lots of things, since it's all different.
None of your parts will work with the 4.0, not even the radiator.
You'll also have to cut and weld the engine mounts, as the frame for the 4 cylinder has different engine mounts than the 4.0. So you'll need welding skills or access to someone who has welding skills.
Keep in mind you'll also need the transmission from the 4.0, as whatever transmission is in your 2.5 will not work.
Yeah I know somebody who is a retired professional welder so I could have him help me with the mounts. My uncle has done many engine swaps so he can help me with the swap too. This is the doner Jeep and the only thing I'd need to buy is a radiator and engine mounts. I was going to buy this TJ anyways just to use as a doner for whenever I need parts and I figured I would do a 4.0 swap too if I got it. Here is a pic of itIt's not worth the effort, you're right
But, if you insist on doing it, the easiest way to do this (hands down) is by having the entire donor vehicle with you so that you have easy access to everything you need (and there will be lots of things, since it's all different.
None of your parts will work with the 4.0, not even the radiator.
You'll also have to cut and weld the engine mounts, as the frame for the 4 cylinder has different engine mounts than the 4.0. So you'll need welding skills or access to someone who has welding skills.
Keep in mind you'll also need the transmission from the 4.0, as whatever transmission is in your 2.5 will not work.
That should do it then! Having the entire vehicle will make life a lot easier! At that point it will literally just be swapping things over as oppose to hunting for parts you need.
My friend is selling a 1998 XJ with a 4.0 for $500 because it's a rust bucket so I was considering getting that but I dont know if the engine mounts are the same on the block and even if they are, I would still have to source a lot of parts
Oh no... DO NOT try and swap the 4.0 from the XJ in, it's a nightmare. The entire engine block is different, as are the mounting points and a host of other things.
@UPJOHN just helped his son do this on his TJ, and I think he will agree with me that next time around, it would be a mistake to use an XJ as the donor vehicle.
Here's that thread just so you can see why swapping in a 4.0 from an XJ is a bad idea: XJ 4.0 into TJ: Hardest engine swap ever
Yeah I was considering taking the risk to save $1000 but I wouldnt not want to deal with all the issues that it would cause while trying to install it
Yep, not worth it IMHO. And even once you get it in and all figured out (not to mention the issues you'll have trying to use the transmission from the XJ), you won't be able to retain A/C (assuming you want to keep A/C).
A TJ is a much better donor vehicle.
:meparto::meparto::meparto:
@Djbtraxxas I’m sure you’ve heard this before but if you’re going to go through all the custom fan work, why not swap in a V8? Not to impede the 4.0 because it is by far the best engine I’ve ever owned. Ultimately it comes down to what you want.
Keep in mind a couple things.
1). There are different variations over the model years. ‘97 is its own breed. Lots of differences from the first year through the rest.
2). The next issue you’ll run into is CCD vs PCI bus. Those are the terms for the way the ECM talks to the instrument cluster, airbags, and PDC. 97-00 was CCD whereas 01-06 was PCI. In addition to swapping the 4.0 and engine harness, I would swap in ALL the dash wiring (if it were me I would just swap in the entire dash) so your dash and interior functions can communicate with the engine and ECM. You might find a few differences like your blower motor for instance. In my 2002 it’s in the passenger footwell whereas in a 1997 it’s inserted into the firewall behind the battery.
Basically I would strip everything electrical from the 2002 and put it in your 97 tub. I’ve replaced a couple of the wiring harnesses before and it’s not hard at all. I’m sure other jeepers will chime in with stuff but this is what came to mind.
This is what I was going to recommend as well. Clearly you know more about it than I do (I didn't know about the PCI vs. CCD), but it's definitely going to be easier if he swaps over anything and everything from the 4.0 in terms of engine, transmission, and the complete wiring harness.
hi guys, sorry to bring back the dead, but when swapping 4.0 to 2.5, does abs matter? does it have any role playing in how the speedo or odo work? got a 97 tj 2.5 w/ no abs, and might have a donor 98 tj 4.0 w/ abs.
Do you know the build date on your TJ? The 97 TJ were started assembly in 01/96 and the wiring from 01-03 1996 had some different wiring which might cause your only problem.
Since ABS was an option a lot of times the same wiring harness if used and then the needed plugs for options are left empty. So as far as I know there shouldn't be any issues with the 98 TJ harness.
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its 04/97, just looked at the wiring diagram, saw 1 wire going to DLC, and 1 to ecu data lines. both pink in color. they start from abs module, 1 pink wire sci tranmit, splits to two lines and 1 going to DLC, and one going to ecu data line
Okay from the information I have you are good. It's the 01-03 96 build dates that has the different wiring. Sorry I just looked at my other post and saw that I'd said 01-04 which isn't correct it's 01-03. Which of course the build date I have on my 97 TJ.
TYVM for confirming. u know where i can get my hands on the engine mount bracket? one that goes on the frame for the inline 6? haha discontinued for years i see haha. possible i can reuse the one from the donor car if its not rusted to hell?
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