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4.0 to 5.9 swap

Old 09-21-2012, 09:02 PM
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Default 4.0 to 5.9 swap

K so i did some homework and heres the deal. My buddy and i are doing r second gas to cummins swap in another ram. So i will have motor trans the wiring harness and computer. Now seems like a good start. I know i will need to order motor mounts. Easy enough. The trans on the 5.9 is 2wd. I have a 42re with 249 tcase. His is 46rh-re. I am hoping i can use that trans with my tail shaft with my tcase?? Cant find a good answer online. Next best thing i assume is buy a trans and tcase from a 5.2 or 5.9 zj. Worst case. Next is the wiring. It probably wont be a great concern but am hoping to use my interior harness and the engine and trans harness or engine to computer and probably relay box?? I am hoping to find some intrest on here for good input from somebody who KNOWS what they are talking bout.
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Old 09-21-2012, 09:38 PM
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You'll need a 4WD V8 trans (short shaft), as that long shaft 2WD trans won't work with a t-case. You'll also need a set of V8 ZJ exhaust manifolds, as I don't believe those Ram manifolds will fit in the ZJ's unibody.
You need to find the engine compartment wiring harness & PCM, and transmission wiring harness and PCM, from a 4X4 V8 ZJ from a donor vehicle.
The Jeep and Dodge blocks may use different mounting patterns, so don't be surprised if you have to make the mounts.
The Dodge intake may be taller so you could have hood clearance issues. I know the Dodge 5.9 R/T engine and the '98 ZJ 5.9 used different intakes because the Jeep has a lower hoodline.
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Old 09-21-2012, 09:53 PM
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Uuuhhhhhh.... Lol. That kinda sucks. All in all i thought it would kinda be cake walk seems i have a donor truck pretty much for the swap but didnt think i would have so many issues. I thought it would be just like dropping a 5.2 or 5.9 from another zj in but guess not. I was looking at some mods and things i would have to pick up but not that much. When we did the gas to cummins swap it was pretty simple but i guess its alot diff. From this. My buddy actually bolted his 2wd tailshaft ont his 4wd trans and it was fine and i did tons of research on that so kinda want to disagree on that. And the motormounts was the laest on my worries. I can make them from the donor truck mounts. Exhaust i just assumed would be the same like tge 5.9 zj. The wiring and compuers was most of my worries.
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Old 09-21-2012, 10:24 PM
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how is a 2wd tailshaft going to work with a 4wd transmission? 2wd tailshaft isnt made to have a transfer case bolted to the back of it. plus the trans from the 4.0 wont bolt to the back of a 5.9, and even if it did, the power of the 5.9 would probably blow the 4.0 trans apart

Last edited by dnuccio; 09-21-2012 at 10:27 PM.
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Old 09-21-2012, 10:37 PM
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The ZJ and Ram use totally different design/shaped exhaust manifolds because with the ZJ's tight subframe rails. The Ram had a lot more room, so clearance for the manifolds wasn't an issue. I read the early V8 ZJ's used the same manifolds as the V8 Dakota's though. Those are easy to find, and flow fairly well.
On the 2WD trans, the output shaft is longer so I doubt it'll work, but I guess you know more than me.
Good luck with this. I know you'll enjoy the V8 as I had a '97 V8 ZJ.
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Old 09-22-2012, 12:02 AM
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Dnuccio, the trans are realistically the same. The tailshaft is like a adaptor to the tcase wich makes it 4wd. U have a 4wd and 2wd trans the same. Take the tail shaft off the 2wd and bolt it directly on the 4wd. Now u have a 2wd trans. Pretty simple. Now 42re and 46rh-re trans are pretty similar from what i have researched granted the 46 is 2wd my tail shaft if it bolts up will allow my tcase to bolt up therefore it will be 4wd. The 42 and 46 determins the internals power ratio. The 46 is stronger to with hold the power hints the reason i am not looking for a adaptor to make my 42 bolt up to the v8. The e is for electronic as for the h is for hydro from my research. All in all if the tail shadt bolts up and i use the engine and trans harness from the 5.9 it will work. I was just hoping somebody would know right off hand if the tail shaft bolts the same to both of these trans? If all fails i get a v8 trans from a zj. Easy enough. I am just trying to get point outs of things u dont always consider like the exhaust manifolds, intake, and i know the radiator might have to change. I know it seems stupid to put the time and money in this but i kinda have a attachment to this jeep and love doin what people say cant be done. The cummins we build is a 2500 single cab shortbed 2wd. Find another one lol. I am just looking for more power out of it. Depending on how much other things i can figure ill run into i may just build a stroker of the 4.0.
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Old 09-22-2012, 01:14 AM
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my point is, its not worth it. if you want a 5.9 in a ZJ, then buy a 1998 5.9 limited. much much less hassle, and that way you know its done right. as opposed to your method of frankensteining 2 transmissions together that were never meant to be that way. even if the tail shaft from the 42re will bolt to the 46rh (idk if it will or not), you will still have that weak spot since the 42re is not meant for the power of a V8.
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Old 09-22-2012, 09:47 AM
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I dont really care for the 5.9 lol i just am gathering onfo on this swap since i have a motor and trans sitting right here. Its funny cuz when i did tryvto research info pn this subject. The threads were full of people saying its not worth it instead of actual knowledgable info. As if u know wats worth my time or money. Thats what makes me want to most of all.
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Old 09-22-2012, 11:25 AM
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However you do the swap, you are going to run into electronic problems you can't even begin to imagine. I just hope you take this into concideration. Of course it can be done, but are you ready to take the time and $$ it's going to require?

There is a lot of satisfaction in building something yourself. When I was younger, we put a Chevy 327 in the back seat of a VW Beetle! Lots of fun until the motor ripped the floor out! We just did this for fun and to see if we could do it.

I love classic cars because I understand them. Once you start throwing electronics into the mix, it becomes intense! Good luck with you project.
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Old 09-22-2012, 12:28 PM
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I've enjoyed reading the above.

I was thinking of fitting an Alfa Romeo 2.4 JTD engine in my 98 XJ 4.0 Auto.

The 2.4 JTD engine is an excellent 5 cylinder deisel engine producing anywhere from 150-207+hp from the factory but with shed loads of torque (225-295 ft lb).

Then I had a moment of sanity and realised this would be a complete headache with ECU's, custom bellhousings and more to worry about.

So I decided to be happy with my 4.0 instead.
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Old 09-22-2012, 08:33 PM
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If I were in your shoes, I'd probably do the swap, but I'd do it the easiest way I could. I'd use as many parts from a donor V8 ZJ as I clould get from the salvage yard. My son found an engine harness for my ZJ V8 when I needed one because a squirrel had chewed through mine. That only cost me $20 bucks at pick a part.
If you get the correct parts, it's just plug and play. A lot less headaches means a lot more fun IMO.

Work smarter, not harder.
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Old 09-23-2012, 12:52 AM
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Very true guys. Thanks for all the input and opinions. I talked with my friend today anx thought some things over. Lookin into the stroker more now too. Althogh my trans is bout to **** anyways i think we goin to hold onto the motor and start looking into a 5.2 or 5.9 trans and tcase. Then its just mounts. A harness and some little things to finish up
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Old 09-23-2012, 06:51 PM
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If your trans is getting weak, you know you'll have to replace that when/if you go the stroker route. That's very easy though.
But either way, you'll love having the extra power available when you need it.
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Old 12-06-2015, 07:47 PM
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How old is this thread? Anyone reading it still? I have a 1996 with a three inch lift. I will have questions on that eventually but for now i am replacing a blown 5.2 with a 5.9 with 155k , warranty for 550. I have researched this a little and see that there is a torque converter controversy. The engine is out of a 1995 Dodge Ram 2500. I know about flashing the computer but do not know how or where to do it. I have read to use the torque converter from the 5.9 and read to not use it since it fits a different tranny, but from the posts i was reading it was unclear it was because of years or the engine size. But i have to know by tommorrow whether or not to buy a torque converter made for the 5.9.
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Old 12-07-2015, 12:49 AM
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You can look up the part numbers for both the 5.2 and the 5.9 and see if they are different. That should help you make up your mind.
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