yj 4.2 to 4.0 swap - JeepForum.com
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post #1 of 17 Old 05-01-2012, 05:24 PM Thread Starter
yamaha4282
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1988 YJ Wrangler 
 
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yj 4.2 to 4.0 swap

In a couple weeks i will be swapping my 4.2l carb engine from a 88 YJ to a 4.0l engine out of a tj wrangler, the transmission is a BA10/5 which will be replaced with an AX-15. I need to know what problems i might run into regarding (Motor mounts, transmission, t-case, Ect.) I also would like to know what parts im going to need besides the motor and transmission of course. Should everything just bolt right up or will other parts be necessary. Thanks!

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post #2 of 17 Old 05-01-2012, 08:38 PM
dodger889
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The right flywheel, for the ECM you are planning to use. I'm not sure if if your TC will work or not. Then what gauges are you going to use and which ECM? It's not the engine and trans that will give you the most problems in most of these swaps. It is the external components and electronics is more of a problems.

A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
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im just cheap, and cheap makes you creative.
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post #3 of 17 Old 05-01-2012, 10:21 PM Thread Starter
yamaha4282
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im planning on using the same gauges if i can. Good thing im doing this swap i tried to start my jeep today and the battery was dead so i charged it. it turns over now but wont start.
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post #4 of 17 Old 05-02-2012, 08:45 AM
wendell
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It would be easier just to build your 4.2. With a few old school parts my 4.2 makes well over 200 hp and there's no computer or sensors to mess with, plus you retain your manual fuel pump. People are to fast to throw the baby out with the bath water. The 4.0 is an awesome engine as I've had a few, but so is the 4.2 witch makes peak torque at 1,800 rpm's. If I had a 4.0, I would keep it, just as I would keep the 4.2. For the cost of the swap, you could of added a 4 barrel, intake, cam, header and so on, or you could inject the 4.2 if carbs aren't your thing. On mine I had installed a holley 470 4 barrel, offy intake, comp cam, rollor rockers, ported head, header, hipo pistons, HEI and MSD, it screams. I can't knock anyone for wanting more hp, but there are easier ways to get it without swapping and adding a computer, wires, sensors, electric fuel pump and so on. Just my 2 cents, 4.0's are great, good luck with your swap.

1987 wrangler, 258 I-6, 5-speed.
2007 liberty sport 4X4, automatic
2009 ford ranger 4x4 FX4 OFF/ROAD, 5-speed
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post #5 of 17 Old 05-03-2012, 03:19 PM Thread Starter
yamaha4282
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I need to replace the engine anyway. If I stick with the 4.2 does anybody know where a good place to buy it? I want to get a long block or does anybody sell a 100% complete motor? because most things under the hood needs to be replaced anyway. Also my tranny is an BA10/5 and I want to put an AX15 in it. If I keep the 4.2 will the AX15 bold straight up or will anything need to be replaced?
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post #6 of 17 Old 05-03-2012, 04:00 PM
94chb
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ive swapped my 4.2/auto to a 4.0/ax15 and LOVE IT!! i got everything i needed from a 91 wrangler.

http://www.jeepforum.com/forum/f12/m...-swap-1290604/

Trying to climb Carb'd
https://www.facebook.com/video/video...37179689658813


Climbing Fuel injected






And a pic of my Current Setup

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post #7 of 17 Old 05-03-2012, 07:31 PM Thread Starter
yamaha4282
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What year is your jeep. And what all did u pull it of that other jeep?
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post #8 of 17 Old 05-03-2012, 08:18 PM
94chb
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Look at the link i posted and you would know. My jeep is an 89
i used engine , trans, wiring harness and under dash wiring harness , fuel pump assembly.
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post #9 of 17 Old 05-04-2012, 01:14 PM
wendell
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The AX-15 is pretty much a straight forward swap behind the 4.2, you will need the t-case for the 15 as well, or swap the shafts.

1987 wrangler, 258 I-6, 5-speed.
2007 liberty sport 4X4, automatic
2009 ford ranger 4x4 FX4 OFF/ROAD, 5-speed
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post #10 of 17 Old 08-15-2012, 11:34 AM
SSRx7
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I swapped a 92 Cherokee 4.0/Ax15 into my 88 yj. I tried the old 5 wire to get it running trick that so many people recommended and it became a nightmare rats nest. So I went on ebay and bought a complete wiring harness (from the front of the jeep to the back) from a 94 wrangler. I pulled out all the old wiring and installed the new ones. I also had to swap out to newer style gauges and tail lites as the connectors are different. Other things you will need are the ecm, vehicle speed sensor, different throttle cable and power steering lines, and an electric fuel pump. The 20 gallon tank in the YJ accepts the factory electric pump and pickup in place of just the pickup, so you don't have to wire / splice in an aftermarket inline pump. Since my engine was out of a cherokee, it had the offset engine driven fan. I went with a strait electric Hayden 16" fan and it works fine, even with the 105* weather we get here in Southern Az. The results of my swap are great. I have a completely uncut wiring harness, all my gauges work fine, and I get pretty decent power and gas mileage.

If you have any question about how I did something, pm me and let me know, I'll tell you how I did it.

Bill
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post #11 of 17 Old 06-15-2017, 04:44 AM
Nixonsbudz
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Quote:
Originally Posted by SSRx7 View Post
I swapped a 92 Cherokee 4.0/Ax15 into my 88 yj. I tried the old 5 wire to get it running trick that so many people recommended and it became a nightmare rats nest. So I went on ebay and bought a complete wiring harness (from the front of the jeep to the back) from a 94 wrangler. I pulled out all the old wiring and installed the new ones. I also had to swap out to newer style gauges and tail lites as the connectors are different. Other things you will need are the ecm, vehicle speed sensor, different throttle cable and power steering lines, and an electric fuel pump. The 20 gallon tank in the YJ accepts the factory electric pump and pickup in place of just the pickup, so you don't have to wire / splice in an aftermarket inline pump. Since my engine was out of a cherokee, it had the offset engine driven fan. I went with a strait electric Hayden 16" fan and it works fine, even with the 105* weather we get here in Southern Az. The results of my swap are great. I have a completely uncut wiring harness, all my gauges work fine, and I get pretty decent power and gas mileage.

If you have any question about how I did something, pm me and let me know, I'll tell you how I did it.

Bill
Sorry I'm replying 5 years later but im doing this exact swap but have a complete running 92 Cherokee. Do I need anything new or will I be able to get everything I need from the Cherokee?
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post #12 of 17 Old 06-15-2017, 02:36 PM
project_mercy
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Quote:
Originally Posted by Nixonsbudz View Post
Sorry I'm replying 5 years later but im doing this exact swap but have a complete running 92 Cherokee. Do I need anything new or will I be able to get everything I need from the Cherokee?
The post you quoted sorta says all the things he did.
  1. He had to find/buy a complete YJ engine and interior harness with all the gauges and the PCM and basically rewired the whole Jeep.
  2. He bought a new fuel pump (and I'm guessing sending unit) and rear tail lights
  3. He also had to convert the speed sensor on the transfer case from cable to electric.
  4. He also changed the throttle cable out and the power steering lines.
  5. He also bought an electric fan and removed the mechanical fan because he said the positioning is different. I'm not sure what the deal is with that, I guess I would just change the mechanical fan so it fit the YJ shroud.

That said, I think there's some steps he didn't mention. I know one step was changing the clock position of the transfer case. I also think he had to do something about the clutch and the input gear on the transfer case. I'm assuming he didn't get the TC with the engine and trans, because he mentions swapping the VSS. Considering how little I know about Jeeps, I imagine there's probably a ton of other little things you'd also have to do. I'm guessing if you keep searching this forum you can piece together the full list. I generally find I can find answers for 95% of my questions here given enough persistence with the "Search this Forum" box at the top of the forum.

He also suggests PMing him, you might try that.

With your help I will resist the urge to buy a chrome grill guard for yet another day.
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post #13 of 17 Old 06-16-2017, 10:20 AM
Nixonsbudz
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It won't let me pm anyone until i have 15 posts. New member. I've got 90% of the info needed from these forums and are very helpful. I guess I was wondering if having a complete donor 92 Cherokee at my disposal if the things he bought could be salvaged from it and fit into my yj. Fuel pump or even the entire fuel tank, mounts, cooling system even if it involved swapping the rad itself. Labor is not an issue but money is. Its also go a 3" body lift. And would i need to clock the transfer case if i took it from the Cherokee as well. Not sure if it's a clearance issue, mounting issue, operational issue, ect
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post #14 of 17 Old 06-16-2017, 01:22 PM
Bobs85Reny
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My son and I are in the middle of a 4.0 conversion right now. on an 89YJ We started with a 99 WJ Grand Cherokee. Its more complicated because it OBD2 so we needed the entire harness from the WJ. Here is the thread.

http://www.jeepforum.com/forum/f22/p...26/index3.html

my son has not updated it in a while but we are near the point of putting the tub back on and have worked out most of the drive train nightmares. Even with an entire donor vehicle there is still a lot we had to get the drivetrain to work. We are 2 years into this swap so far. However we only spend our summer months working on it. Be prepared for a lot of work over just putting back in a 4.2

1. Motor Mounts (We used Brown dog with a 1 inch MML)
2. Clock ring adapter (Transfer case needed to be rotated to fit) Advanced adapters had the clock ring we needed. Note we also had to sleeve the shaft seal for the extra thikness of the clock ring advanced adapters had the that as well
3. Slip yoke eliminator. (Tom Woods) 2 reasons 1 shorten drivetrain length and deal with angle. 2 The wj got its VSS from its abs on tone rings from axle. We neither wanted the ABS and tone rings. By changing out the rear housing and slip yoke we were able to use the tranfercase now for our VSS we just need to calculate what speedo gear we need.
4. New front TC yoke. Rezeppa to conventional yoke. (Tom Woods)
5. 2 New double cardan drivesshafts Front and Rear (Tomwoods)
6. TC drop even with the MML we still had a fairly steep angle. We had installed an OME 2.5 inch lift. but do to the added length of the drive train we still needed a 3/4 inch drop
7. Axle shims (Rubicon express) Still to be installed. With using A double cardan shaft the rear pinion angle needs to be addressed. We ordered 6 and 8 degree steel shims. Once we get this set we will have the shims welded. We still have to work on either axle swap or gearing.
8. Fuel Pump. We are most likely choosing to go with an external on this. (Still to be done)
9. Fuel lines. Mix and match between yj lines and Wj lines
10. Brake lines all new

Still to be done items

11. New brake booster and proportioning valve (Still to be done) Thinking of going with a late model YJ 93 or newer
12. Power steering hoses. (Still to be done) Possibly New Durango steering box still to be determined
13. New radiator / Electric fan. Wj used an electric fan To wide to fit. Likely solution Ford Taurus fan (Still to be done)
14. AC condenser May be able to use the WJ condenser (Still to be done)

This will be where things will get interesting
15 Wiring harness and computer WJ
15. Gauge cluster. The gauge cluster from the wj is part of the ECU Its small enough that I think I can custom fit it. This will require a complete custom dash
16. WJ airbox This will replace the YJ one. Better AC Heat and Blower motor Plus it will wire in to the wj harness
17. Ignition and steering This will also come from the WJ.
18. updated headlights and signals etc.

So with all this still left to be done a 4.0 swap is not just plug and play.
an OBD1 solution from an XJ is an easier solution. However you will still need a late model YJ for the computer and gauges harness etc.
If you have any specific questions Let me know and I will answer whatever I can.
Most of my solutions came from this Forum.
Attached Thumbnails
-5.jpg   -4.jpg   -3.jpg  

Told my girl I just had to forget her, Rather buy me a new cartburettor,
So she made tracks sayin' ths is the end now, Cars don't talk back they're just four wheeled friends now
"Queen"
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post #15 of 17 Old 06-16-2017, 01:36 PM
project_mercy
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Quote:
Originally Posted by Nixonsbudz View Post
It won't let me pm anyone until i have 15 posts. New member. I've got 90% of the info needed from these forums and are very helpful. I guess I was wondering if having a complete donor 92 Cherokee at my disposal if the things he bought could be salvaged from it and fit into my yj. Fuel pump or even the entire fuel tank, mounts, cooling system even if it involved swapping the rad itself. Labor is not an issue but money is. Its also go a 3" body lift. And would i need to clock the transfer case if i took it from the Cherokee as well. Not sure if it's a clearance issue, mounting issue, operational issue, ect
None of those things he listed can you source from the XJ. You may be able to convert some of the things on your YJ to do that. In his post he basically didn't want to hack into harnesses and rewire anything so he bought all new things that plug into the harness. So new tail lights, new fuel pump & sending unit, new gauges, etc. If you had the time and inclination, I'm sure you could make most of those things work by just rewiring it. Solder and shrink-wrap is cheap.

I don't see the purpose on putting in a new rad and electric fan, especially if your current rad works fine. The 4.0L block is the same between the XJ and YJ. I don't know what causes the XJ fan to be offset but I'm sure you can convert it to be like a YJ. At worse I imagine it involves buying a new water pump (never a bad thing) and a fan clutch and fan, and maybe a different belt or something.

The throttle cable you have to buy.

The PS stuff will depend on where the XJ reservoir is. If you had a manual steering box in your YJ, then you don't have to worry about it.

With your help I will resist the urge to buy a chrome grill guard for yet another day.
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