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Moses!

I have a 95 XJ (Project Bumble Jeep) I am building. Mostly stock at this point except for a Zone 3" lift and and all that goes with that. My stock 4.0L runs great but gets only about 11-14 mpg. To be fair I only fill the tank once a month (8k miles in 2 yrs) so I've had to switch to non ethanol (93) fuel. My question is I'm thinking of swapping in a more modern straight 6 (looking at possibly an RB or even a 1J or 2J.) I've been told by some fellows down under these might bolt up to the AX15 without an adaptor plate. This would be great if true. Honestly I jut want better fuel economy. There is a company in Detroit that makes adaptor plates for the AX15 but they are quite pricey (for me) so I've also thinking if swapping is a stock 5.7 Hemi (keeping the AX15). I know most guys that swap in Hemi's go with the automatic which would require extensive modification or the floor. On the non XJ swaps you can get away with body lifts to clear the stock floor. Do you have any info on swapping in RB's or 1J or 2J  with the AX15's? Or can you point me to someone who does. Thanks for your time and any help you can give. God bless and stay well.

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Frank...I'm not clear on your swap engine list if you mean a Mopar RB big-block V-8, Toyota 2JZ, etc., please clarify which of these engines are on your list...The simplest swaps involve the 5.3L GM LS Gen 3 V-8 engine or the Mopar 5.7L Hemi.  Yes, the hemi usually means an automatic transmission, and the AX15 would be questionable for use behind this V-8.  If you're talking about Toyota engines, yes, the AX15 is essentially the same as an A150, R150F and similar "150" designation transmissions used in Toyota trucks and the Supra.  Aisin is the supplier.

The 5.3L GM LS is more popular and easier (relative when it comes to conversions!) to adapt.  Our good friends at Advance Adapters can provide the adapters. Example:  https://www.advanceadapters.com/products/712567--chevy-v8--v6-to-jeep-wrangler-ax15-adapter-bellhousing-kit/.  AA can also provide the motor mount kit, which typically requires some fabrication work.  Here is an example of how that engine fits into a Wrangler: 

https://www.4wdmechanix.com/HD-Video-Advance-Adapters-Jeep-TJ-Wrangler-LS-V-8-Conversion?r=1  [This example shows the 4L60E automatic versus your AX15.]

The LS Gen 3 V-8 is is not only a more orthodox swap, but if done correctly, it can also be emissions legal.  It might be possible to get this conversion approved at California and other states that follow similar guidelines.  See my coverage of conversions and legality:

https://www.4wdmechanix.com/Cummins+4BT+and+4+ISB+Diesel+Engine+Conversions  [Though this is diesel coverage, I devote an entire section to California emissions legality and engine conversions in general.]

I have been a strong proponent of the 4.6L stroker build of the 4.0L inline six;  however, fuel efficiency is never in the cards with these engines.  If I were to do an engine for the XJ Cherokee, other than a stock or 4.6L very mild stroker rebuild (good for another 250K miles), I would do an iron block version of the LS 5.3L V-8 engine.  High tech, plenty of power and likely far better fuel efficiency than the 4.0L inline six, the LS V-8 would take a Jeep YJ or XJ to the next level.  Stock LS Gen 3 power would be substantial, and fuel efficiency would climb considerably with milder use of throttle.

You and your family stay healthy, too!

Moses

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Moses,

Thanks for getting back to me. Not a fan of LS swaps into non GM vehicles. I prefer to keep a Mopar a true Mopar. The RB engines I was referring to were RB 24 and RB 25 (Nissen I think) I was told they would also bolt up to the AX15. If that's the case, it would make for an interesting swap. I've done some checking and I know the AX15 is only rated at 200/300 HP. But I'm not building a rock bouncer or even an off road beast. I'm just looking for better fuel economy. My 4.0L runs great and has plenty of power for what I do, but the mileage sucks. (10-13 MPG)

Even the 5.7 Hemi in the Rams is doing better than that. I've also thought about swapping in the old 225 slant 6 with the fuel injection conversion. 

Any how, I appreciate your input. God bles.

 

Frank

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Frank...As a point of interest, the GM S-trucks with the 4.3L Vortec V-6 used the NV3500.  This is similar to the NV3550 used in post-AX15 Jeep TJ Wranglers.  The GM Vortec (4.3L) V-6 and the V-8 engines share a common bellhousing pattern, too. 

The AX15 will replace an NV3550;  Advance Adapters sells new AX15s for this purpose.  Similarly, the AX15 might mate to a GM NV3500 bellhousing.  (You need to confirm this.)  There may be an easy way to use a GM Vortec V-6 in your Jeep.  Advance Adapters makes motor mount adapters and other pieces to facilitate this V-6 conversion.

A Vortec TBI V-6 or a 4.3L L-34 V-6 would be better on fuel than the Jeep 4.0L...You may be able to do this conversion with factory or recycled parts.  Notably, Howell Engineering makes a GM Vortec TBI wiring harness if you consider a Vortec TBI 4.3L V-6.  You would need the GM ECM and feedback sensors;  make sure these parts are included with the engine package.  Exhaust, cooling and all other swap related details would need address.

Moses

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Moses,

Not even considering swapping in any GM engine or transmission. If it doesn't have 3 pedals. I don't want it. It took me a long time to find to find my 5 speed XJ and not going to give it up for an automatic. I've heard of Advance Adapters. Good product, crazy price. Still exploring options that don't involve GM parts. The Hemi is the most likely swap at this time.

Frank

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Frank...The NV3500 and NV3550 are manual transmissions.  I was not suggesting that you give up the AX15 or a manual transmission.  If I were building a 5.7L Hemi 5.7L V-8 powered XJ or Wrangler with a manual transmission, I would use an NV4500 iron case five-speed.  The Hemi swap has been popular with a Mopar automatic transmission, but I agree, your rarer XJ with a manual ("3-pedal") setup is a prize.  Would have preferred our '99 with an AX15 instead of the Aisin AW4 automatic.  However, the AW4 is a rugged and long lasting transmission that gives the XJ Cherokee a reputation for longevity.  

To beat the fuel mileage dilemma with the 4.0L or inline stroker 4.6L, I considered a diesel R2.8L Cummins and the BT4.   I have the fabrication equipment and over fifty years of engine swapping experience.  From a consumer standpoint, the conversion costs dissuaded me from both engines.  I did a comprehensive article recently, addressing these diesel swaps and including pertinent emissions legality facts.  You can see my comments if interested:

https://www.4wdmechanix.com/Cummins+4BT+and+4+ISB+Diesel+Engine+Conversions

Moses

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Moses,

Thanks for the info, especially on the diesel swaps. I have thought about that as well. I follow Nate at dirt lifestyle on YouTube. He loves his diesel swaps in Jeeps. There are a lot of options when swapping in a diesel. If I had my own shop, that would be a real possibility. But first, I have many other things to finish on the Bumble Jeep (like paint). This nonsense with Corona has things all buggered up for me right now. Hopefully by the time I "retire" a year from August (66 and 2 months) I'll have the XJ and my retirement conversion camper done and I can start to travel some. Thanks again for all your help, I really appreciate it. God bless.

Frank

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