94 YJ swapping in the 4.0 - JeepForum.com
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Unread 06-11-2014, 09:48 PM   #1
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1994 YJ Wrangler 
Join Date: Jun 2014
Location: Rockford, IL
Posts: 4
94 YJ swapping in the 4.0

I have a 94 YJ wrangler with a 2.5l engine, ax5 trans, and 231j t-case. I have a 94 xj as a donor for the 4.0. An 87 yj will provide the BA10/5 trans (i know its crap but its what ive got and cant find an ax15).
What all do i need to do to get it to work right? The trans currently has an AMC 231 t-case mounted to it. The amc and the 231j are identicle when it comes to the bolt pattern right? Also, i heard the trans needs a crank position sensor. I think there is a place to mount it to the bellhousing but i do not know what i need.
Any advice or input on the project would be appreciated.

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Unread 06-16-2014, 11:29 PM   #2
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1994 YJ Wrangler 
Join Date: Jun 2014
Location: Rockford, IL
Posts: 4
I want to use the flywheel and pressure plate from the 4.2l but cant find a sensor that it compatible. Anybody know of one? If not, I will need to get a flywheel for a 4.0. I think the pressure plate will bolt up to it. Anybody have info on this matter?
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Unread 06-17-2014, 07:54 AM   #3
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1995 YJ Wrangler 
Join Date: Feb 2013
Location: Austin, Texas
Posts: 1,874
There are many things wrong here, which is probably why you aren't getting any responses.

First, find a AX15. Hopefully later than 94, so it has the external slave. Otherwise, you'll be trying to hack the CPS onto the old transmission bell housing. Yes, it's possible, if you have a machine shop available.

Second, you can't use the 4.2 flywheel and PP. The flywheel must match whatever ECU that you are using - I'm assuming 94 XJ 4.0L ECU? So you need a 91-98 flywheel, pressure plate and clutch.

Third, you really need to do a bunch more research.

There's wiring details, ECU details, transfer case input gear lengths and spline counts, and I'm not sure that you have taken all these things into account.

Research, research, research...
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