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post #1 of 3 Old 05-14-2019, 06:04 PM Thread Starter
Rob K
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1995 XJ Cherokee 
Join Date: Sep 2007
Location: River Falls
Posts: 1,959
Engine swap and rebuild questions

I have a 1995 XJ with 2.5L and AX5 trans. 180k miles and the engine idles a little rough due to low compression. It's my favorite year and color so at some point I will fix what's left of the floors and replace the engine even though things are getting pretty bad. I just bought a Millermatic 211 welder and I'm fired up to put it to use.

My neighbor just started to part out his 1999 Wrangler because the body and frame are bad. It has the straight six 4.0L with AX15 trans. I think he said 240k miles, runs and doesn't burn oil.

I assume with the proper mounts his engine and trans would bolt into my XJ without to much trouble. Maybe would have to get different drive shafts. What do you all think? If I do this what else should I be harvesting off his Wrangler to make the swap?

My XJ has OBD1 electrical and his is likely OBD2. I don't imagine that's too much of problem since I'm just swapping the engine and manual trans.

Also the XJ is my secondary vehicle. It doesn't need an engine anytime soon so I could also rebuild the the 4.0L before putting it in. I've never done it and it would be good learning experience. What does it typically cost to rebuild and engine if you try to do most of it yourself? I done all my own repairs for 20 years or more, I've never had the opportunity to do a rebuild though. Would it make more sense to put the 4.0L in and rebuild it later when it really needs it? Obviously it would make sense to at least replace the freeze plugs.

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post #2 of 3 Old 05-16-2019, 03:02 AM
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1981 CJ7 
Join Date: Jul 2009
Location: Bali
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I assume both are 4WD?

You may both have an NP231 with a driver side drop to the front axle. I would check this before doing anything else, as it will be comforting to know it will drop into position and your issues are concentrated in the engine bay.

Forward of the bulkhead you should be thinking of retaining the harness and boxes from the Wrangler. teh 2.5 and 4.0 are different, eliminate this straight away.

You will then need all sorts of bits from a 4.0 HO Cherokee to finish the swap off from exhaust manifolds to air cleaners. There may be a long list.

Once you have it running, you may need to change the axle ratios.

Cost of rebuild can be as low as $1000. Darn sight easier before you put it in, energy evaporates over time on these projects.

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1981 CJ7 258ci - Bagusjeep
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post #3 of 3 Old 05-16-2019, 09:20 PM Thread Starter
Rob K
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1995 XJ Cherokee 
Join Date: Sep 2007
Location: River Falls
Posts: 1,959
Thanks for the extensive reply. Yes both are 4x4. Mine has NP231 transfer case, D30 front axle, C8.25 rear axle, 4.10 gears. The part you don't think about is all the bits that will get the drive train linked up to the XJ. From what you said and thinking on it, that list can be pretty long. This would be a lot easier if the donor vehicle was an XJ. Maybe it makes more sense to rebuild and turn the 4 cylinder into a fresh 2.8L stroker. Or maybe just another XJ completely with 4.0L/AX15/NP231. I'm really fighting giving up the one I have though. I'll think on it.
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