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Old 08-01-2011, 08:38 AM   #1
Join Date: Nov 2010
Posts: 8
91 Comanche 4.0 into YJ swap questions

I got a line on a 4.0L from a 91 Comanche for a good price and am thinking about picking it up to swap into my 92 YJ. I've searched and have found a few answers but still have some more questions.

I'm going back and forth between picking up an AX15 or an AX5, as the engine doesn't come with the trans or transfer case. I know I can use either, but are there pros/cons as it comes to ease of swapping? Can I grab just about any year?

Can I re-use my stock rear end?

I'll need a stock 4.0 front and rear driveshaft, correct?

What harness should I use? I'm thinking I'll have to pick up a harness and ECU for the 91 comanche and splice it into my YJ body harness?

What all is needed for the swap?

Thanks in advance for all the help, to return the favor I'll keep this thread updated with pictures and hopefully turn it into a How-To worth being stickied.

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Old 08-01-2011, 08:44 AM   #2
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Location: North NJ
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The AX5 is not well known for it's durability or strength. I'd go AX15 if i were doing the swap. From Novak conversions' page:

"The AX5 is prevalent, but sadly it's strength is minimal, making it a questionable off-road transmission. Failures behind even stock engines are not uncommon. We do not make any conversions components available to retain the AX5 with six or eight cylinder engines."

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Old 08-01-2011, 08:54 AM   #3
Join Date: Jul 2011
Posts: 107
AX5 sucks... AX15 is much better. The stock 4.0L drivelines should work. Make sure you aren't going to have any emissions issues... some areas require that the engine be the same year or newer than the body it goes into.

The Comanche harness MIGHT be able to be used as stock... if it plug into the bulkhead connector with everything in the right place. The sending units and such should all be fine.
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Old 08-01-2011, 09:29 AM   #4
Join Date: Nov 2010
Posts: 8
Color me retarded, I meant AW4. I have an AX5 in my 2.5 now and honestly that's 75% of the reason I want to do the swap in the first place, because it's so weak. Editing first post.
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Old 08-01-2011, 09:51 AM   #5
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In that case, it's mainly going to break down to personal preference. Do you enjoy driving an auto or manual more? If you go auto, remember to get an external transmission fluid radiator. All of the Jeep auto transmissions have a bit of a habit of overheating if you ride the torque converter on obstacles or crawl up hill for an extended period of time.

I'm no expert, but Novak implies that you HAVE to have the PCM from an '87 to /01 Jeep 4.0 to control the electronic shift points on the AW4. Make sure you have that wiring harness worked out before you pull the trigger. Either your YJ or the Comanche PCM should work, as long as they don't have different plugs.

The Jeep AW4 Transmissions - Novak Conversions
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