4.0 conversion....help - JeepForum.com
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post #1 of 30 Old 06-02-2016, 10:34 PM Thread Starter
CherryYJ
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4.0 conversion....help

So I'm fixing to start on my 4.0 conversion in my 1989 Jeep Wrangler that's currently a 2.5 TBI.

I currently have a 1994 XJ 4.0(that was mated to an automatic)with the engine and the computer/ECM. I have a 1994 YJ 4.0 engine wiring harness. I have an ax15 with a NP 231 with 23 splines.

My question is I was told that I have to have a 4.0 ECM that came from a manual jeep, and that the intake engine harness and computer need to be from the same 4 0 manual yj.

I was also told that the obd1 ecm doesn't control the trans and that the engine harness computer just needs to be a 4.0 and the same year range 91-95 4.0

Is that right. I find it hard to believe that the current parts I have won't mess together perfectly.


PLEASE HELP. :-) THANK YOU

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post #2 of 30 Old 06-03-2016, 02:33 AM
jsawduste
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As long as you ground circuit T41 and the donor doesn't have anti theft you can run any combination.
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post #3 of 30 Old 06-03-2016, 04:09 AM
xeroid81
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If the donor 4.0 from the xj is connected to the AW4 trans then it's controlled by the TCU which would have been located behind the dash panel by the glove compartment on the donor vehicle. Are going to use the ax15 you have or the aw4.
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post #4 of 30 Old 06-03-2016, 06:43 AM
jsawduste
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Which is a very true statement. However the ECM doesn't care.

Ground T41 and drive it.
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post #5 of 30 Old 06-03-2016, 09:04 PM
mattsez
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the auto in a wrangler isnt ecm controlled.....and a stick dosnt care.
I am however wondering how your going to make a trans and transfercase from an xj work in a wrangler....transfer case clocking is different. Front drive shaft will hit, i assume its the same with a manual . Trans support.....drive shafts......4:11 diffs .....wow theres gonna be alot of issues.
Ecm will be easy.....plug and play.
Honestly....lol.....id buy a good running basket case with a 4.0.....and use the 2 to make one......save you ALOT of head aches
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post #6 of 30 Old 06-04-2016, 12:30 AM
jsawduste
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Doesn't say he is going to reuse the XJ auto/TC.


Reread the question.
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post #7 of 30 Old 06-04-2016, 03:14 AM
xeroid81
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He doesn't appear to have made up his mind which way he's going probably because of some misinformation he's gotten. One being the roll of the ECM controlling trans function./ That's why I corrected his inquiry in line 4 of his post. It should be obvious by now that I,as well as many others on this forum,have done this conversion. I used the complete drive train from an XJ with no major problems. I kept the AW4 for the overdrive. Kept the 4.11 also with no problems. I didn't have to reclock the case,no problems with the front drive shaft. You have to move the motor mounts IF YOU GO WITH AUTO ONLY. Manual would not be a problem. Also 4.11 aren't a problem with overdrive 4th at .75:1. As far as the tranny mount I made a simple adapter using 1/2' " plate stock with 4 holes drilled in it. It's not that complicated when you figure out what you want to do.I would refer the OP to read the FAQ'S on this subject. Plenty of info there from guys who have done this successfully.Again it depends on what his goals are and what he's trying to accomplish. I agree the ax15 swap would be the easiest route to go if that's what his intentions are.
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post #8 of 30 Old 06-05-2016, 08:35 AM Thread Starter
CherryYJ
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I'm only using the 4.0 and the ECM. Trans/tc are both from wranglers. Completely taking out 2.5/ax5/21st line np231.
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post #9 of 30 Old 06-08-2016, 12:00 AM Thread Starter
CherryYJ
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Quote:
Originally Posted by xeroid81 View Post
He doesn't appear to have made up his mind which way he's going probably because of some misinformation he's gotten. One being the roll of the ECM controlling trans function./ That's why I corrected his inquiry in line 4 of his post. It should be obvious by now that I,as well as many others on this forum,have done this conversion. I used the complete drive train from an XJ with no major problems. I kept the AW4 for the overdrive. Kept the 4.11 also with no problems. I didn't have to reclock the case,no problems with the front drive shaft. You have to move the motor mounts IF YOU GO WITH AUTO ONLY. Manual would not be a problem. Also 4.11 aren't a problem with overdrive 4th at .75:1. As far as the tranny mount I made a simple adapter using 1/2' " plate stock with 4 holes drilled in it. It's not that complicated when you figure out what you want to do.I would refer the OP to read the FAQ'S on this subject. Plenty of info there from guys who have done this successfully.Again it depends on what his goals are and what he's trying to accomplish. I agree the ax15 swap would be the easiest route to go if that's what his intentions are.
You sir are correct I'm getting my marbles all gathered up. I want there to be no curve balls once it comes to actually doing the swap.

I am using an AX15 which a great friend of mine is rebuilding for me.

As for earlier someone said T41 circuit?what is this and where can I find it.

Another question I have yet to find out the 1994 electrical system have/require a electronic speedometer sending unit (my 89 is cable driven)

Discussing the conversion with my friend he said the Tach will be different too.

Things needed still please let me know so far my understanding I need these)
1. ax15 np231 linkage (jeep used parts specialist says my ax5 linkage won't work with the ax15)
2. YJ motor mounts on the block (I have xj passenger and driver side)
3. Front drive shaft(supposedly the 2.5 ax5 fron and rear shaft won't work?
4. Tachometer
5. Power steering lines for the newer style power steering pump since my current one on the jeep is the single v belt(gm style pump)
6. There is what appears to be a switch on the ax15(do happen to know what it is)


Again thank you for all your help appreciated more than you know.
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bruinjeeper and CWBreeding like this.
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post #10 of 30 Old 06-08-2016, 12:02 AM Thread Starter
CherryYJ
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Quote:
Originally Posted by jsawduste View Post
which is a very true statement. However the ecm doesn't care.

Ground t41 and drive it.
t41????
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post #11 of 30 Old 06-08-2016, 12:06 AM Thread Starter
CherryYJ
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Also think I figured out my fuel pressure fix. Airtex E7311 it shows this as being a factory drop in fuel pump on advanced autoparts.c o m BUT it has min70psi to max90psi pressure. Anyone seen this swap. Only noticeable difference is that the ends on the fuel pump in the tank are blade style this have threaded terminals so I'll just switch the ends to eyelids to over come that issue*does this work?*
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post #12 of 30 Old 06-08-2016, 08:03 AM
jsawduste
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Quote:
Originally Posted by CherryYJ View Post

As for earlier someone said T41 circuit?what is this and where can I find it.

Another question I have yet to find out the 1994 electrical system have/require a electronic speedometer sending unit (my 89 is cable driven)

Discussing the conversion with my friend he said the Tach will be different too.

Things needed still please let me know so far my understanding I need these)
1. ax15 np231 linkage (jeep used parts specialist says my ax5 linkage won't work with the ax15)
2. YJ motor mounts on the block (I have xj passenger and driver side)
3. Front drive shaft(supposedly the 2.5 ax5 fron and rear shaft won't work?
4. Tachometer
5. Power steering lines for the newer style power steering pump since my current one on the jeep is the single v belt(gm style pump)
6. There is what appears to be a switch on the ax15(do happen to know what it is)


Again thank you for all your help appreciated more than you know.
T41 grounds the coil side of the relay.
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post #13 of 30 Old 06-08-2016, 09:27 AM
xeroid81
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Nice pics. As far as the concerns and questions you post,I didn't have any of those particular problems because I had a newer YJ. I also used the whole XJ drive train including the AW4 trans with the mated TC.I would advise you to check out the archives for the write ups on the 4.0 conversions. Maybe you'll find the answers for your specific questions.I believe you can use the same motor mounts. I cut and relocated mine up forward about 3" to compensate for the longer trans and motor.The hard part was the harness.The wires were not the same colors between the 2 vehicles so there was a lot of splicing. I didn't know about the spline count and length of the input shaft being different until I started putting it together.I guess I was lucky the guy still had all the parts I needed . I basically installed a 93 xj drive train in a 95 yj. Hope yours turns out okay! Love the header. What make is it? I used a dynomax originally but since changed to a stainless steel Gibson due to rusting.I mistakenly tried to use the xj downpipe but reordered the yj type so everything would line up correctly.I wasn't thinking at the time I guess.I also went with the advance adapter tc linkage conversion.It was much cleaner to install.
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post #14 of 30 Old 06-08-2016, 04:11 PM
rocketboy
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Jsawduste can correct me if I'm wrong but T41 is the circuit for the neutral switch on the automatic transmission. You ground it if you aren't using an automatic. Do you have the factory service manual with the wiring diagrams? You're going to want it.

An observation: the back end of your exhaust header is supposed to be attached with a stud/belleville washer/nut. Yours appears to be missing. It's common for the studs to break and then you have to remove it with an easy out and then replace it. If you don't replace it there's a good chance of getting an exhaust leak and then getting check engine codes and/or it will run rich. The job isn't too hard if the engine is on the stand. When the engine is installed it's a PITA to do. Ask me how I know...
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post #15 of 30 Old 06-08-2016, 08:37 PM Thread Starter
CherryYJ
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Yeah funny you say that. The previous owner snapped it off. :-(

Sucks working for the uncle Sam and not having a few bucks to spend on some nice upgrades. I've been deal hunting for 3-4 months now. Even with all the deals I'm steal roughly at 1600 into this swap so far.

Maybe you can answer this question for me. The 4.0 needs minimum of 43psi(fron what I've read) the yj 2.5 fuel pump puts out 30-46psi at like 30gph. I found an airtex E7311 f/p that puts out 70-95psi @ a flow rate of 30gph but the 94 4.0 f/p puts out about the same pressure @ 70-101/110psi @ 40-55pgh( will thay 10-15gph difference screw me into starving the motor or over working the pump?

Also advanced auto parts shows the E7311 as a replacement drop in fuel pump. can the factory 2.5 TBI regulate that 70-95psi down to the 18-20psi the tbi needs to run on? Only reason I'm asking is because I want to bring the jeep to someone who's interested in driving my jeep with the current drive train to sell it to him.

Thank you everyone you all are awesome!!!
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