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Discussion Starter #1
I've searched a bit before I stepped up to my own thread but didn't find any specifics on a TJ 4cyl. to a 6cyl. swap.

I have a 2.5l 97 automatic and looking do to a 4.0l swap. I presume the easiest way would be to get another OBDII engine from a TJ. My questions are, do i need the engine AND transmission? What complications will I have with the wiring, and so on?

I really need any help and pointers I can get. I do not have a FSM for the TJ. If anyone knows the best place to get one, that would be VERY appriciated. Thanks for any help!
 

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It is best to get the whole engine/trany/TC combo from the donor TJ. You can only reuse your TC if you change the input gear shaft to fit the 6 cyl trany.
 

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You can get the FSM from the dealer. I also believe a guy on Ebay had them on disk.

I know the 2.5 is a little short on the power side but unless the little beast is just plain worn out, you may consider gearing changes instead. I swapped in D44's from a Waggy with 5:13's and now I turn 35's with ease and I get 5th gear on the highway.

Swapping the engine can open a HUGE bag of worms unless you're ready. The tranny in your Jeep won't hold up to anything other than the 2.5 (even if it would bolt up) and the input shaft is different on the t-case from a 6 cyl. Dropping a 4.0 in is no easier than any other engine swap. A good canidate you may want to consider is a chevy 4.3 v6.

If you do an engine swap you're gonna want to change axles too. The stock stuff under your jeep now is marginal at best - throw even more H.P. at it and watch 'em go.

I know this is a LOT to digest but I believe that you have to troubleshoot all the options when taking on a task this big.

Good luck on whatever you decide!!!
 

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As far as the Tcase goes, it seems i can retain the 231 i have from what was said in this thread: http://www.pirate4x4.com/forum/showthread.php?t=242490

right now, the rig is on 36's with 4.56 gears. If it was a stick, it might be better, but the auto hurts it. I wheel with other guys with near similar setups, just a 6 instead of a 4 and its night and day.


i have an 8.8 in the back and a stock 30 up front, detroits in both. I've been wheelin it for a while and its rough just to drive around being so powerless.

I was hoping that the 4.0l from the equivalent year would be the easiest switch than anything..as far as motormounts, tranny mount, wiring, etc... I'm not afraid to change tranny mount if i have to and do a little wiring.
 

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crawlnTJ said:
As far as the Tcase goes, it seems i can retain the 231 i have from what was said in this thread: http://www.pirate4x4.com/forum/showthread.php?t=242490

right now, the rig is on 36's with 4.56 gears. If it was a stick, it might be better, but the auto hurts it. I wheel with other guys with near similar setups, just a 6 instead of a 4 and its night and day.


i have an 8.8 in the back and a stock 30 up front, detroits in both. I've been wheelin it for a while and its rough just to drive around being so powerless.

I was hoping that the 4.0l from the equivalent year would be the easiest switch than anything..as far as motormounts, tranny mount, wiring, etc... I'm not afraid to change tranny mount if i have to and do a little wiring.
It's already been said but you will need a new tranny. The AX-5 is only light duty and has 21 spline output. The AX-15 has 23, so your NP231 input shaft will need to be changed to 23 spline input.

Easiest route to go is buy a similar year 6 cyl TJ and swap the axles and other mods. Sell the 4 popper Jeep to recover some cash. But where is the fun in that?
 

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Discussion Starter #6
I have an auto...isn't the ax-5/15 manual tranny's? I figured i would get the tranny with it, but was just worried about the tcase. ..and according to that thread, the input shafts will not need to be changed.
 

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crawlnTJ said:
I've searched a bit before I stepped up to my own thread but didn't find any specifics on a TJ 4cyl. to a 6cyl. swap.

I have a 2.5l 97 automatic and looking do to a 4.0l swap. I presume the easiest way would be to get another OBDII engine from a TJ. My questions are, do i need the engine AND transmission? What complications will I have with the wiring, and so on?

I really need any help and pointers I can get. I do not have a FSM for the TJ. If anyone knows the best place to get one, that would be VERY appriciated. Thanks for any help!
Private message Peran on the board. He has some nightmare stories about his 2.5 to 4.0 swap and what NOT to do.
 

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If your gonna do an engine swap, do it right....go V-8. There is no more work sawpping a v-8 in rather than a 4.0. The one benefit of the 4.0 is that your guages will work. Other than that, everything will need to be changed....motor mounts, radiator, driveshafts, trannys, tcase.....
Josh
 

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Jeepin5.0 said:
If your gonna do an engine swap, do it right....go V-8. There is no more work sawpping a v-8 in rather than a 4.0. The one benefit of the 4.0 is that your guages will work. Other than that, everything will need to be changed....motor mounts, radiator, driveshafts, trannys, tcase.....
Josh
ditto...
 

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Discussion Starter #11
I would v8, but the thought of breaking everything doesn't sit easy. I dont think i really 'need' a v8, plus I was hoping to hear that taking a 97 TJ 2.5l and putting a 97 TJ 4.0l in it would be the near easiest way to go. any more info on that?
 

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been there done that, its freaking easy as hell. just need the motor (complete) compy and front engine harness, and make motor mounts. not hard at all
 

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Sell your Jeep and buy one with a 4.0. Most likely going to be cheaper and it's a hell of a lot easier.
 

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Discussion Starter #16
Chris... u used the stock trans...stock rad?


Tornado... I've had the jeep since almost 97 and have a lot of time and money in it. I'd be more willing to just do the swap.
 

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Do you want to stay auto? dont think you said yes or no. The only auto to even consider for a 4.0l is the aw4 and it takes a lot of work to do in a tj. BUT you could easily get the entire donor from a rolled XJ including the 231, you would just need to redrill the mounts so the t-case is clocked right, 6 holes and easy.

Wiring is whats gonna bite you in the ass to run an aw4, any tj trans would be an easy swap, just get the wires/clutch etc. Engine needs the ECU/entire wiring harness form the engine bay and the like. For the work either stroke it or v8 it a stock 4.0l aint worth the hassle
 

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The first thing is to decide how you are going to use this rig and do you have to smog it. Then you need to decide how much work you wnat to do, ie; fabrication, cooling exhaust and as mentioned the instruments. From the 4.0 on up you are going to need to change the transmission. My .02 is that the 4.0 OBDII is the easiest for you as a lot of the components are already in place. Do the reasearch and buy the Service Manual. If you can get a donor from the same year it should be almost plug and play. I put a "98 TJ 4.0 in my '84 CJ7. A fair amount of work but the end result has been most satisfying. Just keep in mind that somebody is always gonna be bigger, bader and break more. So what is your threshold of pain?
 

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Discussion Starter #20
I do have an auto and wasn't planning on swapping to a stick. If the aw4 is an XJ 4.0l tranny, does a TJ 4.0l have something different? I was planning on just getting the whole engine trans.

I dont have to worry about smog at all. I could run open headers around here if i wanted. I wouldn't run a cat, but i would still have everything running properly....not skimping on wires, etc.

I was thinking of going v8 if this is going to turn into something of equal difficulty. Maybe trying to keep it obdII i should look for a 97-98 grand cherokee 318?
 
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