Thanks for the detailed and quick reply Moses, very interesting tech. I think you're right it is probably multiple worn parts making clattering together. I am looking forward to tearing down this engine one day and seeing how it looks/checking the wear. This is Mike at MCE Fenders (MCE Mike on Facebook) and this is the lime green Jeep in our photos. (Also emerald green before it was painted) I've owned this Jeep since I was 16 in 2000.
You are absolutely right, this is a testimonial for this engine. I am absolutely amazed at how problem free and durable this engine is. Since it doesn't have much power, and had larger than stock tires on it since ~60,000 miles, this engine spent a lot of time at full throttle and/or high RPM. It has had 31s and 4.10s for a few years, 33s and 4.10s for about 6 months, 33s and 4.88s for a few years, and has been on 35s with 4.88s since 2008. I could also go on about all the times it spent revving high in the snow, breathing dust in the Moab and PNW silt, and it has overheated a few times due to a water pump and electric fan issue. I always just kept the oil changed.
I am probably not going to do an engine swap for a while - just not enough time right now and focusing on other Jeeps and the company, but am collecting ideas on what to do. I am definitely leaning towards a small V8. I don't want a huge powerhouse, I rather have reliability of the entire Jeep rather than a HP number on paper. So was thinking a Vortec 4.8 or possibly a 5.3. From the research I have done, the Magnum 5.2 and 5.9 are the "easiest" swaps for my TJ electrically, so those are also on the drawing board.
One other idea is to try 505 Performance's new 2.5L stroker kit and head. (2.7 and 2.9 options) But I am still researching this. While the sound and power of a V8 is fun, keeping the light 4 banger but adding power might also be fun.
In '08 I swapped the AX-5 for an NV3550 with junkyard parts, and bolted on a NV241-J to that. So I am thinking they will be fine with either option. The front axle is a high pinion 30 out of a Cherokee. This would probably be fine for the stroker 4 cyl. option, but probably need replacing for the V8. This Jeep doesn't have a rear axle at the moment, but it will probably get a D44 when I have time to get to this project.
Too many options, haha!