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Unread 05-01-2012, 04:24 PM   #1
yamaha4282
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1988 YJ Wrangler 
 
Join Date: May 2012
Location: college station, texas
Posts: 6
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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Unread 05-01-2012, 07:38 PM   #2
dodger889
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1989 YJ Wrangler 
 
Join Date: Jan 2009
Location: mi
Posts: 4,161
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.
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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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Unread 05-01-2012, 09:21 PM   #3
yamaha4282
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1988 YJ Wrangler 
 
Join Date: May 2012
Location: college station, texas
Posts: 6
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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Unread 05-02-2012, 07:45 AM   #4
wendell
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1987 YJ Wrangler 
 
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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.
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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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Unread 05-03-2012, 02:19 PM   #5
yamaha4282
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1988 YJ Wrangler 
 
Join Date: May 2012
Location: college station, texas
Posts: 6
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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Unread 05-03-2012, 03:00 PM   #6
94chb
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1989 YJ Wrangler 
 
Join Date: Dec 2009
Location: Whitwell, TN
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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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Unread 05-03-2012, 06:31 PM   #7
yamaha4282
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1988 YJ Wrangler 
 
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Location: college station, texas
Posts: 6
What year is your jeep. And what all did u pull it of that other jeep?
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Unread 05-03-2012, 07:18 PM   #8
94chb
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1989 YJ Wrangler 
 
Join Date: Dec 2009
Location: Whitwell, TN
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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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Unread 05-04-2012, 12:14 PM   #9
wendell
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1987 YJ Wrangler 
 
Join Date: Aug 2006
Location: grafton ohio
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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.
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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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Unread 08-15-2012, 10:34 AM   #10
SSRx7
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1988 YJ Wrangler 
 
Join Date: Jul 2012
Location: Huachuca City, Arizona
Posts: 366
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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engine swap , transmission

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