XJ engine swap feasability

So in one of my bored on a saturday googling for jeep things moments, I came across a post talking about the 3.5l V6 that Chrysler put in the 300m in '99, being an aluminum block and heads and doing 250 hp. A little more research told me that it was designed to be mounted longitudinally and mounts to the 42LE auto.

Then I figured out that the 42LE was modified by Chrysler for the liberties and wranglers into the 42RLE and they bolted a 231 to the back of it. So that got me thinking. An HO version of an all aluminum V6, controlled by late 90's Chrysler computers, SOHC and putting out 250/250 hp and tq and theoretically mounts to an already existing 4wd Jeep tranny/tcase package.

What's not to love here? Is there a reason this hasn't been a viable engine swap for XJ guys? I mean other than the fact that the 4.0 lasts a long time and it's not getting you V8 power, it's still bumping up the performance, maybe the mileage, and it could plug itself into the gauge package without any fuss.

Tell me I'm crazy. These cars down here are $700 on craigslist all day.

Re: 3.5l engine swap feasability

Humm.

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3.5l engine swap feasability

There's a Libby trans and tcase on craigslist up here for $125. Saw it yesterday looking at tractor parts.

Re: 3.5l engine swap feasability

RedHeep said:

Is there a reason this hasn't been a viable engine swap for XJ guys?

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Yeah, probably because the XJ only came with either an AX15 manual or an AW4 automatic, and the Chrysler 3.5 V6 doesn't bolt up to either of them. Therefore to make the engine swap viable, you'd also have to swap in a new tranny so it ain't worth it when you have the simple option of building a 4.6L stroker that can put out the same 250hp (at much lower rpm) but with 60lbft more torque.
____________________________________________________
1992 XJ 4.6L "Poor Man's" Stroker
202rwhp @ 4700rpm (248bhp)
258rwtq @ 3400rpm (311lbft)
1/4 mile: 14.63 @ 94.4, 3450lb curb
Stroker build-up, Stroker "recipes"

Re: 3.5l engine swap feasability

Those 3.5s aren't very reliable....

Re: 3.5l engine swap feasability

The fact that the 42RLE is the worst transmission ever made along with horrible TCM programming is a good reason not to do this. I love my LJ, but I hate driving it because of the dumb transmission that I had to replace already. :/

Re: 3.5l engine swap feasability

This sounds like a lot of work to step in a different pile of dog crap. And that pile of dog crap is the 42rle.

If you want to do an original v6 swap in an xj I would put a supercharged 3800 in it. You'll do just as much work in wiring and there are existing bell housings that bolt it up to an aw4. The aw4 IMO is the best light duty auto out there, and unless you are swapping in a 5 speed or a beefy Chevy auto anything else just seems like a step down. I've always wanted to do a 3800 swap into a jeep I just haven't had a good project vehicle for it.

Re: 3.5l engine swap feasability

First, not being reliable I would disagree with. The engine was in production for 19 years in a mulitude of platforms. Second, that transmission came in a lot of Jeeps and while maybe not the best option, certainly not the worst.

Strokers are not plug and play. I wouldn't even bother building one if I was going to spend the same amount of money on a 5.3 swap. I get the love of the 4.0 and I understand the v8 swap mentality.

I don't want to be different, I'm just trying to figure out why not. Not because you don't like the idea, but technically why not. What's preventing me from mechanically and electrically putting this engine/tranny combo into an XJ?

Re: 3.5l engine swap feasability

I would take a Peugeot BA10/5 manual from a Cherokee over the 42RLE. One must drive a Wrangler with a 42RLE transmission to truly feel how bad it is. The bad TCM programming is part of why it has so many issues. For example, the AW4 will properly sense engine load and demand properly downshifting when going up hills as needed without hesitation. The 42RLE will sit there with the accelerator floored with the engine lugging half way up the hill until finally decides to downshift. The majority of my driving experience with the 42RLE is hitting the Overdrive Off switch like it is a manual transmission. In short, the 42RLE will suck a considerable amount of power out of the engine while not acting like a good automatic transmission.

Strokers are plug and play with a fuel injector upgrade. They are an attractive option especially if building it yourself.

As for the mechanical side the 42RLE in the Wrangler uses the 4.0L bell housing bolt pattern and does not have a removable bell housing. I believe a 42RLE from a 2005-2010 3.5L Dodge Charger would work, but then it is a 2WD transmission. However, I do believe the rear outputs are swappable.(Fact check this, please.)

The electrical issue will come down to that the 42RLE uses a dedicated TCM that is reliant on the PCM. So whatever TCM that works with the 42RLE you source will need to be compatible with the TCM you choose.

Re: 3.5l engine swap feasability

I love an underdog engine swap as much or more than the next guy.
That being said...
It's going to involve exhaust, driveshaft, linkage, wiring, coolant plumbing & a ton of other stuff to make it work. There will be zero aftermarket parts designed to help you along the way.
It's a ton of work, for a Chrysler V6 & crappy transmission.
Why not do a ton of work and get a bitchin' Chevy V8 with an awesome transmission?
If it would really honestly be cheap / easy to set up the Chryco V6 then that's one thing, but I don't think it would be any easier than an LS swap. It's cool to be different I guess...

Re: 3.5l engine swap feasability

Alexia said:

So whatever TCM that works with the 42RLE you source will need to be compatible with the PCM you choose.

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I can not edit posts so all of you get this useless post with my correction.

Re: 3.5l engine swap feasability

I agree with yossarian19. Any engine swap is a lot of work, why not make it worth it? You can do a ls swap for what you will end up spending on this.

Re: 3.5l engine swap feasability

I have a Pacifica in my shop with a bad 3.5 in it. After looking at it and the reman that came from Chrysler...

No, not in a million years would I want one in a Jeep.

99SJ 'Still putting it back together' Ex

Re: Re: 3.5l engine swap feasability

99SJ_Ex said:

I have a Pacifica in my shop with a bad 3.5 in it. After looking at it and the reman that came from Chrysler...

No, not in a million years would I want one in a Jeep.

99SJ 'Still putting it back together' Ex

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Exactly how I feel and how I came to that conclusion lol

3.5l engine swap feasability

RedHeep said:

What's preventing me from mechanically and electrically putting this engine/tranny combo into an XJ?

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Nothing. Anything is possible, but its a debate of function at this point. Im not sure it has enough function to warrant the extra considerable effort and compromise in components. And i think even if you built it you would would look at an ls powered jeep and wish you spent your money on that.

If you're dead set on an odd engine swap then go for it. I like odd shit, and i would look forward to how you would solve a lot of the design riddles it would present.

Re: 3.5l engine swap feasability

RedHeep said:

What's preventing me from mechanically and electrically putting this engine/tranny combo into an XJ?

Click to expand...

nothing more than would prevent you from doing an LS swap...but with an LS swap you have a million more options for aftermarket support including computers, adapters and performance upgrades, not to mention you get a transmission that was designed for a truck and not a minivan. if you look long enough you can find rusted out trucks with LS drivetrains for less than 1k...so it just seems like a huge waste of time when you will be doing the same amount of fab work. you will still have to find a way to get all the electronics to be happy since you are basically creating the bastard child of an xj, liberty and a 300m. i'm also going to guess that 250 is pushing that motor pretty hard, which means more stress on motor parts and a larger likelihood of failure.

feasible...sure, anythings possible with the right amount of money...in the long run, it doesn't seem like the best option

Re: 3.5l engine swap feasability

And for the record my dream odd engine swap is a Lexus 1uz to an aw4..... Easier than you think.

Re: 3.5l engine swap feasability

I'm not advocating some sort of change to everyone's mindset here, but it is a little concerning that some of you haven't bothered to read, but simply offer an opinion.

The 3.5 has forged internals, free floating pistons, cross bolted 4 bolt mains and 4 valves per cylinder. I don't see how 250 hp is pushing it too hard. I've read a few threads on other boards about boost and tuning because it was stout.

I get that an LS swap is the flavor of the month or that I can avoid swapping a drivetrain with a stroker. Both of those come with their own host of problems, such as cooling an LS with a $600 radiator or working out the fuel management of a stroker. An LS swap also means a custom gauge package, hood and accessory clearance issues and most importantly, me breaking stuff with 350 hp under my foot.

I was hoping to engage in a technical discussion on how to make this work, rather than a discussion on why it wouldn't. Can the 3.5l talk to the jeep gauges? Is there a way to mate the 42RLE to the engine and make the computers talk together? Does the bellhousing even mount to it?

I understand the work involved. I don't need a lesson on an engine swap. I've ridden in an LJ with an auto and it drives just like my XJ with an auto. I guess the technical expertise of is limited to don't do it because no one has ever done it before.

Re: 3.5l engine swap feasability

RedHeep said:

I was hoping to engage in a technical discussion on how to make this work, rather than a discussion on why it wouldn't. Can the 3.5l talk to the jeep gauges? Is there a way to mate the 42RLE to the engine and make the computers talk together? Does the bellhousing even mount to it?

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Alexia said:

As for the mechanical side the 42RLE in the Wrangler uses the 4.0L bell housing bolt pattern and does not have a removable bell housing. I believe a 42RLE from a 2005-2010 3.5L Dodge Charger would work, but then it is a 2WD transmission. However, I do believe the rear outputs are swappable.(Fact check this, please.)

The electrical issue will come down to that the 42RLE uses a dedicated TCM that is reliant on the PCM. So whatever TCM that works with the 42RLE you source will need to be compatible with the PCM you choose.

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http://naxja.org/forum/showpost.php?p=246143335&postcount=9

Additionally, newer TJ gauge cluster components could be retrofitted into a XJ cluster housing if a newer PCM was used to run the engine.

Re: 3.5l engine swap feasability

whether or not PCM talks to guage cluster is going to be dependent on what language they both talk.

I would make the assumption that they're both j1939, in which case yes, 300M PCM should talk to late model XJ cluster.
some things in the PCM might need to be chnged to get them to read properly, depending on idiot lights or full cluster in the donor. Anyone that can tune the PCM could do that.

42rle was also used in durangos/dakotas/1500s. Only difference I've seen is they got an electronically shifted t-case, but you can adapt them to a manual linkage, or just bolt a 231/242 to it. I know that the dakotas of the era got a 233, it looked identical other than a shift motor. Probably be easier to find one in a pickup than a liberty. I wouldn't be worried about the factory performance, because some software changes all of that. I'd make a bet that they were programmed to hold a gear as long as possible for EPA nonsense. Jennie's 01 is the same way, whatever mercedes did to the TCM programming was bad, I'm always manually dropping it out of OD, it's particularly stupid because you have to hit the brakes at 65 to shift it down... I hate that thing.


No comment on the motor or its durability, but I surmise that most problems relate to maintenance, just like any other complicated OHC motor. Don't change the fluids and bad things happen.