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2.5 to 4.0 swap in TJ

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40K views 23 replies 17 participants last post by  2000TeeJ  
B
#1 ·
ok so heres the deal. i currently have a 97 TJ with a 2.5 that has 160,000 miles on it. needless to say, its on its way out. so instead of putting another 2.5 in, i want to put a 4.0 in. i have an AX-15 and NP231 from a 1990 4.0 XJ. i also have a wiring harness, computer, intake, air box, etc. from an 1989 4.0 XJ. i havn't found an engine for it yet. i was told to get a 4.0 h.o. out of a cherokee because it has more power and will bolt/plug into what i already have. anyway, the engine isn't my concern as i can make motor mounts and get driveshafts and all of that.

my concern is the wiring from the 89 XJ to my 97 TJ. i am wondering if there is anyone out there that has done this swap (XJ 4.0 to TJ 2.5) and was successful. if so, can you share what i'll need to consider or wiring diagrams, etc. i have an 89 XJ service manual and also one for my TJ. i guess this will give me a starting point as far as wiring, but i was wondering if anyone had anything with better detail. the digital odometer and speedometer concern me too because the XJ is cable driven. is there any solution for this problem too?

thanks everyone .. hope i get some good help out of this.

-Bob
 
T
#2 ·
The 89 won't be an HO motor. Therefor you would have to get a non HO motor if you want to use the wiring harness you have. The 89 also used the Renix fuel management.....ick. The easiest swap is 91-95 cherokee's/YJ's engines, because they are OBD I wiring/fuel...etc. It's very simple and easy to wire up. The 96-up stuff can be done, and has been many times, just takes a little more patience, as there are more sensors, etc to satisfy regards to wiring.

Granted, mine was a YJ....but the principle is the same.

The removal of the 4banger is very very easy. I had the whole pig out in a mornings work.

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The cherokee driveline is a little harder to remove, simply because you have to be careful of the wires you are pulling. It's more tedious than anything.

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Once those are out, simply get YJ motor mounts and move them forward approximately 3-4"...depending on fan application. Weld them in and set the pig.

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Once thats done, wiring and such...again application specific. The AW4 works great. I'd never go back to a manual tranny on the trail again. The engine has butt loads more power than the 4 banger. The swap can easily be done with out tearing it down to the frame. The I6/AW4 pig is longer than the 4banger drivetrain...so shortening the driveshafts will have to be done as well. The tcase does hang down a bit more....but not much. I cut a small portion out of the skid to allow the drivers rear corner to hang down the 1" below the skid. Granted, I'm SOA...but I've never hit that tcase. Worth every skinned knuckle, wife yelling, no money greasy fingernail moment.

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B
#3 ·
hey thanks man for the info and pics. i will let you know how the swap goes when its in progress/over. can i ask you for help if i need it when i'm doing the swap? it stinks i can't use an H.O. motor, but i think there will be a helluva lot more power from 4-6 cylinders.
 
T
#4 ·
Your TJ is OBD 2, you are going to have to have a computer AND engine harness from a TJ. If you get those it is just plug and play.. As for the motor it can be any motor you will just need the proper intake for it. I just put a motor from a 94 into my 99 tj that had the 4 cyl in it,,
 
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P
#6 ·
why are you going to an old motor? why dont you try and track down another tj motor? I know the cost is abit more. But you can get an adapter for mating the new 4l to your old tranny, it's new on the market, it either comes from novak or advanced adapters.
 
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B
#7 ·
I am in the process of doing this right now. I have the engine tcase and transmission in and running. Still buttoning little things up. Get an engine harness for a TJ and an OBDII computer and just put it in. You won't have to do any wiring on the inside of the jeep. The harness that goes across the firewall and into the jeep just plugs into the computer nothing needs to be changed, at least in my situation but I used an XJ computer and TJ harness from the same year 98. The engine harness plugs into the computer and the 2 plugs in the middleof the firewall and runs all the way back to the gas tank. I was going to use an XJ harness until I got started doing it and quickley changed my mind because it was a wiring nightmare.

Pallister

I think the adaptor you are thinking about is to put a 4 banger to the AX15 not 4.0 to AX5
 
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C
#8 ·
I have done the swap in my 95 YJ. I used a 94 XJ driveline and the XJ harness had a different plug into the firewall, so that guy that did the electrical just wired in the 2 extra cylinders into my 2.5L wiring harness, and all is good. He did use the XJ computer.
 
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W
#9 ·
I just swapped a 5.2 and automatic out of a 97 ZJ into my 97 TJ that had a 2.5. All in all it was a really easy swap. I did tons of research before I did my swap and I suggest you find a complete engine/wiring/comp out of a jeep that is a 97 or newer. It will make the wiring a million times easier. Your stock dash and emissions equip will work with all OBDII engines. Just get a fsm for your TJ and the jeep the engine came out of and slpice wires as needed. On my swap I only needed to swap out 2 connectors in the engine harness and it worked perfectly.


You can bolt that AX15 and 231 to any 97+ 4.0 and 5.2 AND 5.7 Grand Cherokee/ Dakota engines (diffrent bellhousing for V8)

Your 231 will bolt up to all the automatic trannys used with above motors.

About the spedo? You just need a vehicle speed sensor for your 231. your stock tcase should have this..... swap it out.

Hope this helps
 
G
#11 ·
bfoster129 and wahzoo are both pointing you in the right direction. Do you have to pass emissions? If so I would think very strongly about going with a '97 or newer 4.0 HO that is already OBDII and if you can get one from a
TJ the fan is not offset and is one less problem. In any case it is best if you get the engine/ecm/all emission components/and harness all from the same vehicle. Anyway it will make you feel like you got a new rig. I did mine 3 years ago
 
B
#12 ·
yea, unfortunately i do have to pass emissions. i'm pretty sure i'm now convinced to use a 4.0 out of a 97+ TJ or XJ. looks like i'll be trying to sell off all the older stuff that i don't need now.

one question:
will the 89 XJ AX-15 and 231 t-case work with the 97+ 4.0?
 
C
#13 ·
I can't see why not they would not work. Also just so you know the XJ t-case is clocked a little lower than a YJ and I believe TJs
 
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S
#15 ·
Im interested

I dont mean to hijack the post, but I figure its better to discuss in the same post than start a new one thats basically the same.

Anyhow, this is a swap that Ive been seriously considering for my '01 2.5L TJ. Im in florida so i do not have to pass any emissions. Does this mean I can use a 4.0 engine/tranny/harness/computer setup from any year jeep? what about mixing and matching the years?

For you guys who have done this, how much did you end up spending total? I cant imagine this being too expensive if coming from a salvage yard.
 
J
#16 · (Edited)
ok so mine was a yj also but the research done was exhausting . You have an obd-II computer and trying to splice into it is next to impossible(people have said they've done it but its nothing but problems) . For your motor you NEED a computer and engine compartment harness out of a 97 to 06 tj and I would even spend more for the 97 and up 4.0 motor as you will be nickle and dimed for all the right sensors and fittings for them(until 95 the sensors are all 9.something volts and obd2 are 5 volt so they won't interchange. For your tranny you need to know if you have an external slave on the new ax15 like your ax5 all the clutch parts are interchangeable if you have a 94 or newer ax14 otherwise you will have to convert your GOOD external to an inferior internal slave. The parts to swap the internal to an external are pretty easy to find you need a bellhousing (94 or newer) a input bearing retainer, throwout bearing and thats it your ax5 shift fork is the same as the ax15.

Ok so my 200 cents hope it helps

oh yeah the radiator is the same also you just need a lower hose and you can cut the upper. You can also buy pretty new motor mounts from the dealer for about 90 bucks and they fit the contour of the frame perfect for the location
my whole project cost about $2200 getting parts at cost through my work including the motor and tranny, the atlas was 1350
 
T
#17 · (Edited)
OK again, I just did this swap in my 99 tj with the 2.5. If you have the 2.5 you will be required to cut off your old motor mounts and weld new ones in the proper place...I was fortunate enough to get a 6cyl frame at no cost so I skipped that step. Also if you have the 2.5 and go to the 4.0 HO you will need to run a fuel line to the fuel rail because the 4.0 HO has a feed and return line on the rail and the 2.5 does not. You will also need a computer and engine harness from a 97 to 2000 TJ, in 01 they changed some things. Now as far as what motor to use. You can use ANY 4.0. If you use an XJ motor, you will need to get an intake from a tj and the alternator bracketry off of a TJ motor so that you can eliminate the fan AND move the alternator into the proper position because it hits the frame (see my thread "My Build", in the jeep hardcore). Also you will need to change the center pully to one from a TJ so it can accept a fan, unless you plan on going electrical. Also, I found recently that there is also a difference in the steering column mount on the frame between the 2.5 and 4.0...it is currently hitting the motor mount on the 4.0 frame(I will fix this weekend). Now as for the trannys...if you do this swap from a 2.5 you will alson need to aqcuire a tranny AND tcase. The 2.5 tranny AX5 will not bolt up to the 4.0 block. Also, the AX5 tcase is 21 slpine and will not fit the 4.0 trannys because they are 23 spline(although you can change the input spline). If you try to use the XJ tranny you can, but like was mentioned above, the tcase is clocked lower (rotated) by 10 degrees, so you would need to clock and redrill holes in the tranny. If you have any questions on this or anything I have done to mine (only original thing is the body) you can send me a pm here or preferably go to my site www.nwfl4x4.com...

Stantjeeper I am in the panhandle of florida....
 
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W
#18 ·
this may be crazy but you may get more just a little more power out of a sbc or a 318. i could be wrong but this seems like the thing most people are doing and it won't be much harder than a 4litre unless you have a truck with a 4 litre sitting beside you. Its just an idea:smokin:
 
D
#19 · (Edited)
You don't give alot of details on your TJ, but unless you've done a ton of mods to it ( like put a better rear axle and installed a long arm kit and cut the frame mounts off etc) sell your 2.5L TJ and buy a TJ with a 4.0 if that's the motor you want and then get one with a D44 when you do. By the time you blow a bunch of cash on the engine swap you'll be too broke to upgrade the D35 (unless you have already done this).

At least work up the costs to see how much the swap is going to cost and compare that to the price difference for selling yours and buying another. If you factor in your time too then I'm fairly sure it will be more cost effective in to just get a different TJ with a 4.0 already in it.
 
B
#20 ·
i don't have that kind of money to just go and buy a 4.0 TJ. i have way too much time and money into my TJ (with the 2.5). i'm not just going to sell it and lose all that stuff. i could buy the 4.0 TJ and switch all my parts to it from the one i already have .. but again, i don't have that kind of money to go buy another rig.

looks like i'm keeping the 2.5 for now .. at least until it blows up. i like to be different anyway.
 
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