1. #1
    Bigfork's Avatar
    Bigfork is offline Junior Member
    Join Date
    Aug 2017

    Converting from the 2.5L to the 4.0L

    I'm interested in changing out the 2.5L 4-cylinder for the 4.0L 6-cylinder motor for my '92 base YJ. I'm trying to get educated in what is involved. On the highest level, I know there are 3 important steps in the process.
    1. Get a 4.0 liter motor
    2. Remove 2.5L motor
    3. Install 4.0 liter motor

    I am wondering what else is involved or needed. For example: Are the engine mounts in the same location? Does the drive train match up? Is the transmission that comes on the 2.5L version sufficient for the increased HP and torque? Do other pieces parts need to change if the motor changes? That sort of thing. I'm assuming I can keep the same side-view mirrors and so forth.

    I apologize if this question has been asked ad naseum in the past. I did some searches on the existing threads but for whatever reason did not see the answer there already.

    Thanks in advance.

  2. #2
    stumblnyj's Avatar
    stumblnyj is offline Senior Member
    Join Date
    Mar 2012
    Maryland USA

    Re: Converting from the 2.5L to the 4.0L

    I was looking into doing this same swap. I ended up doing a Chevy 350 swap. The motor mounts will need to move forward on the frame. The AX5 would work but depending on how you drive it may hold or may not hold up. I had a hard time finding odds and ends parts that you don't think of or realize you need for the right price (everybody want new prices for 20+ year old parts). So I decided to do the SBC swap. Parts are plentiful and usually in stock at your local parts store and a dime a dozen. I used an adapter kit to mate an AX15 trans (trans that goes with the 4.0) behind the motor for the time being. I'm happy with the end result but eventually when funds are restored I have plans to put heavy duty axles and other beefier upgrades in the future. Hope this helps you along your journey.

  3. #3
    Bounty__Hunter's Avatar
    Bounty__Hunter is offline Moderator
    Join Date
    Nov 2002
    Southern Illinois

    Re: Converting from the 2.5L to the 4.0L

    Old post from an apparent one-and-done member.

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