YJ 4cyl to 6cyl - JeepForum.com
 
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post #1 of 13 Old 09-10-2017, 06:41 PM Thread Starter
Uncleford
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YJ 4cyl to 6cyl

Hey guys,

I've been looking around through the forums trying to find info on this swap and other upgrades. Many of the links are unfortunately broken.

I have a 95 YJ 4cylinder and the frame has rotted pretty bad so I bought a 93-95 YJ frame except it was for a 6cylinder. I know that the engine mounts are in different places and I don't really want to mess with installing/welding new engine mounts in so I figured that maybe I could do a 6 cylinder engine/trans combo and drop my 4 cylinder body on top of it.

I have a line on a 98' TJ 6cyl with computer and harness. Problem is before I commit to buy, I wanted to make sure of a few things:

- Will the 98" TJ 6 cyl drop right in on the 93-95 YJ 6 cyl frame? (meaning bolt right onto frame mounts)
- Will the steering box for a 95 YJ work on the 6 cyl YJ frame and 98' TJ 6cyl
- Am I correct in assuming the transfer case from my YJ 4 cyl will not bolt up to a 98' TJ 6 cyl engine?
- I know the 4 cyl transmissions are mostly junk so what other 5sp transmissions will work with the 98' TJ 6cyl.

I have been searching and will continue to search but if anyone has some first hand knowledge I would appreciate it. Thanks!


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post #2 of 13 Old 09-11-2017, 06:50 AM
fishadventure
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Quote:
Originally Posted by Uncleford
Hey guys, Will the 98" TJ 6 cyl drop right in on the 93-95 YJ 6 cyl frame? (meaning bolt right onto frame mounts) - Will the steering box for a 95 YJ work on the 6 cyl YJ frame and 98' TJ 6cyl - Am I correct in assuming the transfer case from my YJ 4 cyl will not bolt up to a 98' TJ 6 cyl engine? - I know the 4 cyl transmissions are mostly junk so what other 5sp transmissions will work with the 98' TJ 6cyl. I have been searching and will continue to search but if anyone has some first hand knowledge I would appreciate it. Thanks!
You can use the 98TJ engine... but I would source a 91-95 YJ computer and merely add the two extra injector wires. Not whole thing to obd2. It's not quite that simple but pretty close. You will need YJ sensors and stuff. You will need to have the correct YJ 6 motor mounts.

The 4 cyl AX5 bellhousing will not work for the 6cyl. You need an AX15 and bellhousing, and that means either swapping the input shaft or getting a different NP231 to fit.

Yes you will need a new rear driveshaft to use the six.

There's other transmissions (that will, "work with a six") but why?! The transfer case and AX15 is plenty rugged enough and it doesn't take any figuring out, and they're inexpensive. (DON'T get a BA10!)

Shackles and D-rings: different things!
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post #3 of 13 Old 09-12-2017, 06:44 PM
jsawduste
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The TJ engine block has the cast in engine mounts in a different location than a YJ.
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post #4 of 13 Old 09-13-2017, 01:34 PM
Luuca
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Quote:
Originally Posted by jsawduste View Post
The TJ engine block has the cast in engine mounts in a different location than a YJ.
I don't believe that to be true on 4.0s prior to 2000 for the TJ. 97-99.

Do you have a source for that? I know I swapped in a TJ engine 4.0 int my kids YJ but we welded the engine mounts in place based upon the engine/trans alignment in the frame. So they may be different than trying to use a factory YJ 4.0 frame side mounts.

91 YJ "Alice" 4.0L, AX-15, NP 231 Flange, Adams Driveshafts F/R, 2.5" OME 36Rs, 5/8" /f12 Booms, 32" Yoko ATs, 4.10 D30/35 AutoLockers F/R
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post #5 of 13 Old 09-13-2017, 02:26 PM
jsawduste
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Hmmm, you may be right on the prior to 2000.
Get the block casting number and Google the applications.
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post #6 of 13 Old 09-13-2017, 03:42 PM
jsawduste
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I stand corrected Luuca


97, 98 TJ uses the same block mounting points as the YJ.


In 99 they change.


Stinkyfab or BrownDog both show this in their product listing.


On JeepStrokers the FAQ`s/Engine Blocks also makes this distinction.
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post #7 of 13 Old 09-14-2017, 07:32 AM
fishadventure
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Quote:
Originally Posted by jsawduste View Post
I stand corrected Luuca
97, 98 TJ uses the same block mounting points as the YJ
In 99 they change. Stinkyfab or BrownDog both show this in their product listing. On JeepStrokers the FAQ`s/Engine Blocks also makes this distinction.
Good to know. I had 'thought' he was good with that block, pretty sure anyway, but when I saw your post I just assumed you were correct!

Shackles and D-rings: different things!
Cranking IS turning over
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post #8 of 13 Old 09-14-2017, 12:56 PM
Luuca
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Quote:
Originally Posted by fishadventure View Post

Good to know. I had 'thought' he was good with that block, pretty sure anyway, but when I saw your post I just assumed you were correct!
Back on topic, i would take a lobg look at the engine bay harness and decide if you want to find a 6cylder engine bay harness or modify your 4 cylinder harness. IMO buying a good factory harness used is quicker and cheaper in the long run u less your akill set amd love is hunting down wires and soldering. You will need a 6 cyl computer out of any manual XJ or YJ as well AFAIK.

91 YJ "Alice" 4.0L, AX-15, NP 231 Flange, Adams Driveshafts F/R, 2.5" OME 36Rs, 5/8" /f12 Booms, 32" Yoko ATs, 4.10 D30/35 AutoLockers F/R
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post #9 of 13 Old 09-15-2017, 02:46 PM
StanF
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I've done that swap (98 TJ 4.0L into 95 YJ 2.5L)...here's a couple of helpful threads:

http://www.jeepforum.com/forum/f12/1.../#post19892297

http://bb.bc4x4.com/showthread.php?1...nto-94-XJ-OBD1


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post #10 of 13 Old 09-19-2017, 05:38 AM Thread Starter
Uncleford
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great information guys, thanks for all the input. I am looking into the harness. This engine supposedly comes with the 98' computer and engine harness. Is there a separate harness besides the engine harness?

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post #11 of 13 Old 10-19-2017, 05:16 PM
Juegernaut
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Hey,

So I'm going to hijack this a bit here, I'm looking at doing the same swap. Complete 99 TJ drivetrain into my 95 YJ. The TJ this is coming out of is in fine running condition, if I harvest the ECU and harness from the TJ, I'm thinking that I shouldn't need to do any splicing or major modifications. That being said this is my first engine swap so I'm just trying to wrap my head around what I need to do so I'm not completely unprepared.
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post #12 of 13 Old 10-19-2017, 05:43 PM
Luuca
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The issues with using the TJ harness will arise in a few places;

1. Connector ends - the TJ will have different connector ends for the sensors. Your sensors will want to stay 95YJ so your gauges and computer will read correctly.

2. The Bulkhead connector and the wiring from the firewall back are going to be different. You can't just plug and play the TJ harness. This is why I suggested getting a 1995 YJ 6-cylinder harness and either a 6 cyl manual XJ or YJ computer. By using the YJ harness, your connectors will all be the same, the bulkhead will line up the wires properly, and the computer will work on the first fire. Yes, you can use you 4cy harness and extend the Alternator wires, the Coil Wires, and add in two more Fuel Injector wires into your 4cy computer - IT WILL WORK - but for me, the guy who hates electrical work, getting the harness you need is cheap enough not to have to eff with it at all. It's plug and play.

my 2

91 YJ "Alice" 4.0L, AX-15, NP 231 Flange, Adams Driveshafts F/R, 2.5" OME 36Rs, 5/8" /f12 Booms, 32" Yoko ATs, 4.10 D30/35 AutoLockers F/R
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post #13 of 13 Old 10-20-2017, 10:33 AM
project_mercy
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What Luuca said is spot on (which is always true). You really REALLY don't want to try to tie the TJ harness in. It took me probably 8-10 hours to just repair a 6cyl YJ harness I got off E-bay.

In addition, you will probably not have a spot on the TJ head to screw the your temp gauge sending unit in. So you will either have to leave it off, move it somewhere else, or drill and tap a new hole in the head for it. I opted for the "move it somewhere else" and used an aftermarket thermostat housing ( http://www.hesco.us/products/7882/co...-housing-hfth2 ) The only bad part about it is, the sender is pretty long due to how it normally fits in the head, and that means that when you screw it into the thermostat housing it blocks a lot of the flow back from the heater core. I plan on putting an extension on it so it moves the sender out some so just the tip sits in the flow. I've been meaning to post a thread/pictures on it since this comes up a decent amount, but some HomeDepot delivery guy smashed into my internet cable and ripped it out and they haven't gotten to fixing it yet.

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