I'd like to ditch my 2.5

I have a very straight 96 two door with a 3" lift... and 225/75/15s. It looks sharp on 17" ATs, but the 2.5 can hardly push them. I'd like to swap the 2.5/AX5/231 for a 4.0/AW4/242.

I have a YJ that needs an AX5, figured I'd just swap the whole mess as a complete assembly into it. This saves me from putting a perfectly good running engine on the ground to ruin. It also provides a home for the old harness, and to ditch the TBI in favor of Chrysler MPI, but that's another topic in itself.

I have an 86 two door with a 4.0/AW4/231 in place of a 2.8/AX5/207. It can't be as much work as that was. The firewall and core support are the same for the most part in later models. What I'd like to do is leave the dash harness alone. I know the engine harness will have to change, as well as the computer, and it'll need accommodation for the TCM too. I'd be pretty happy if I could just replace everything forward of the bulkhead connector and run the existing fuse panel without having to splice anything. I'd be really happy if it looks like it came that way from the factory.

I know a 96 donor would be ideal, even (or especially) a two wheel drive, but would any OBDII donor work just as well? I find donors all the time, but looking specifically for a worthless 96 two wheeler is taking longer than anticipated.

I assume the dash harness is identical between two door or four door, four cylinder or six, but I know there's some differences between 95-96. If the bulkhead connector is pinned the same it'll be an easy swap.

Why a AW4 out of curiosity? If it was me, I'd be trying to find a 4.0 with an AX-15. Granted, that seems to be the one that everyone and their grandma wants so they command a bit of a premium price, but you're getting a deeper first gear (even the factory final drive ratio is deeper on stock 3.07 5-speed gears vs. stock 3.545 automatic gears.) the final drive in overdrive for the AX-15 running stock gears is taller vs the AW4 running stock gears (despite the AX-15 having a slightly deeper overdrive, 0.79 vs 0.75),

Everything you need is pretty much already there and cut out (shifter location, slave/master cylinder, etc.) so the whole install would be a lot simpler than sourcing the electronics, shifter, cable, cooler lines, etc for an AW4, PLUS, as long as you run the right fluid in the AX-15 (Long story there and, I suspect, also part of the reason these things command a premium price.) she's a skookum choocher.

Just my $0.02, I'll get off the soapbox now. It may just be that I don't like the added complexity of slush boxes...

The '96 has always been a problem year as far as electronics go. The engine itself doesn't matter but the transmission does. You would need a wiring harness and ECU/TCU at the minimum.

Because it's cheap, durable, and I'd rather have an automatic. For no more than I care for the manual truck I already own, I wouldn't pay anything extra for the same experience with more power. I put an automatic in place of a manual in my 86, and didn't consider it any trouble at all. All the parts are boxed should the need for them arise.

I have two AW4s and one AX5 registered and insured at present, and the manual transmission sees the least miles. It's like a backup, despite the fact that there's nothing wrong with it. Given my experience with the 86, the only thing I think I could enjoy more with 4.10s and the AW4 would be AWD. I could build something I really enjoy for less that the price of one used AX15 that may even need work.

I have six Cherokees for parts at present, ten total. The only thing I really need to source is an OBDII wiring harness for a 4.0. I'd buy another complete Jeep for the right price just for that.

Most would say it isn't worth the effort to put a 4.0 in place of a V6, but I had a good time making that swap work, and it cost less than $500 to build. I really enjoy the results, too. Still has the 2.8 emblem.

RCP Phx said:

The '96 has always been a problem year as far as electronics go. The engine itself doesn't matter but the transmission does. You would need a wiring harness and ECU/TCU at the minimum.

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I used a transmission from an 89 in my other 96 when I converted it to 4WD about ten years ago, and it's still going strong, or do you mean the wiring in the dash harness is different between the auto and manual? This is an important point to me in this particular project. I'll change the dash harness if need be.

It's my experience that the engine harness will include the PCM and the TCM harness, which to my knowledge is not connected to the dash harness although it mounts under the dash.

I guess I should look at the interior fuse panel for a TCM fuse or equivalent. Perhaps a manual equipped vehicle would lack that fuse and related wiring. That would tell me if the power to the TCM comes from the PCM, along with TPS signal, etc.

I'm hoping it's all self contained within the under hood harness for an automatic equipped vehicle.

the 96 is obd 2. more wires to run inside to feed the data port, they have a diffrent guage clsuter, the 96 is eletric speedo, 86 is machanical. 96 fuel pump is diffrent. and i think the tcu for the 96 is part of the ecm, where as the 86 is two seperate entities.

Dragonlich1961 said:

the 96 is obd 2. more wires to run inside to feed the data port, they have a diffrent guage clsuter, the 96 is eletric speedo, 86 is machanical. 96 fuel pump is diffrent. and i think the tcu for the 96 is part of the ecm, where as the 86 is two seperate entities.

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Yeah, I know all this, as I already built the 86, drove it for six months, and broke it. It's OBDI now, has a VSS and electronic cruise, 4.0/AW4/231. I replaced the entire dash harness and spliced the old body connectors to it so it plugs in.

What I'd like to know is if there's any difference in the dash harness between 2.5/AX5 and 4.0/AW4. I kind of doubt there is, but it would be nice to have a definitive answer. In lieu of this, I'll figure it out on my own when I get there and act accordingly.

I'm pretty sure the TCM circuits are all contained in the engine harness, besides the part which passes through the firewall to the TCM itself, which doesn't connect to anything else under the dash.

I'll have to pull the dash to add the the TCM circuit anyway because it routes behind the HVAC cabinet, and the knee bolster gets replaced with one that has studs for the TCM itself.

FWIW, any AW4 TCM will plug into a 96 and work, up to 96.

I could use verification that any OBDII harness will work. That would be nice.

Overland said:

I could use verification that any OBDII harness will work. That would be nice.

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Nope, the harness's are quite specific to the year/options.

RCP Phx said:

Nope, the harness's are quite specific to the year/options.

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Sorry, I meant between 94-96. I know obviously anything from 97-01 isn't going to work. I'm hoping anything with an airbag will be similar as I'm sure the Saginaw equipped models are different.

Then again, I could always use an older dash harness, swap in a Saginaw column, and have a nice leather wrapped wheel. I'm both cheap and impatient, but at least I know what I can do, even if it's not exactly what I want.

96 was the first year of OBD-II. 94-55 will be OBD-1.

Dang.

Looks like I'll be going OBDI if I don't find a 96 donor this year.

You really need a 96 donor for it to all bolt in. There are going to be fairly minor differences harness wise (I think, don't quote me on this...) plugging a 95 engine bay harness into a 96 bulkhead connector. You'd want to carefully compare pinouts on the bulkhead connector in 95 and 96 FSMs.

4 vs 6 cylinder does not matter for anything dash electrical on 91 and later, so that's no concern. It doesn't matter on RENIX either, except that the tach will be wrong, but that's neither here nor there.

You really want to aim for a 95 or 96 as the cruise control wiring, plugs, and switches are the same those two years - they use the early Chrysler column instead of the old GM one used till 94 or the new Chrysler column used in 97 and up.

The TCU is NOT part of the ECU on 96s. Well, not exactly. On 4 cylinder 91 and later autos, there is a PCM instead of a TCU and ECU. All 4.0L auto XJs use an ECU and a TCU. However, the TCU plugs into the engine bay harness on a branch that sticks through a big rubber plug on the firewall, so just use whatever TCU comes with your harness and drivetrain and it'll be fine.

The NSS is different 96 down vs 97 up. The entire harness interface from interior to engine bay at the bulkhead/firewall is different on 97 up anyways though so you can't use those donors regardless.

The 96 uses a single returnless fuel rail system but if you swap the fuel lines and fuel pump assembly from a 95 it'll be fine, though you will have to splice the harness to make a 91-95 fuel pump assembly plug into the 96 body harness. You might have to swap the instrument panel too, I'm not 100% sure if 91-95 vs 96 clusters have slightly different fuel gauge guts. Or you can put the returnless rail from a 96 on your 95 motor, cap the vacuum line that used to go to the FPR, and bolt it right in. Might need the fuel line from the filter to the rail off a 96 4.0L donor, but not sure. The rail and fuel line are small enough to be cheap at a junkyard either way.

Cliff notes: You can use whatever 91-01 donor you want depending on how much work you want to put in, but if you go 97 or later, or 90 or earlier, you are in for some serious pain, and if you use a 91-94 you are in for almost as much pain, so for your sanity you really should just use a 95 or ideally a 96 donor.

You really need a 96 donor for it to all bolt in. There are going to be fairly minor differences harness wise (I think, don't quote me on this...) plugging a 95 engine bay harness into a 96 bulkhead connector. You'd want to carefully compare pinouts on the bulkhead connector in 95 and 96 FSMs.

This is good to know. Fortunately, type 56 pins are easy to remove and relocate in the bulkhead. I should really own a few of those manuals.

4 vs 6 cylinder does not matter for anything dash electrical on 91 and later, so that's no concern. It doesn't matter on RENIX either, except that the tach will be wrong, but that's neither here nor there.

That's a good point, because if I found a 96 donor for the engine wiring harness, I could pull the dash to add the TCU circuit without having to undo all of those dash harness retainers that always break.

You really want to aim for a 95 or 96 as the cruise control wiring, plugs, and switches are the same those two years - they use the early Chrysler column instead of the old GM one used till 94 or the new Chrysler column used in 97 and up.

Thanks, I didn't know what year they started with the Chrysler column, and had always assumed it to be 94. That's one year I haven't owned yet.

The TCU is NOT part of the ECU on 96s. Well, not exactly. On 4 cylinder 91 and later autos, there is a PCM instead of a TCU and ECU. All 4.0L auto XJs use an ECU and a TCU. However, the TCU plugs into the engine bay harness on a branch that sticks through a big rubber plug on the firewall, so just use whatever TCU comes with your harness and drivetrain and it'll be fine.

I've covered this in previous posts. While it enters the firewall, drops behind the HVAC cabinet, and goes to the TCM on the knee bolster, it doesn't connect to anything else inside the cab. I didn't know there was a difference with the 2.5 autos, but I should have known because to my knowledge they didn't come with the AW4.

The NSS is different 96 down vs 97 up. The entire harness interface from interior to engine bay at the bulkhead/firewall is different on 97 up anyways though so you can't use those donors regardless.

Right. I have an 01 that donated the engine, tinted glass, and door seals for other projects. I look forward to using the AC components in a 90 I'm also building at present, but don't see a whole lot left in it I want to use. The seats are uncomfortable and I never cared for the Dodge Neon style interior. If you can suggest anything else which might be desirable for use in an early model, I'm all ears. Otherwise, the body remains as parts storage. There's a 4.0 and an AW4 sitting inside it, with a few transfer cases and various other parts.

The 96 uses a single returnless fuel rail system but if you swap the fuel lines and fuel pump assembly from a 95 it'll be fine, though you will have to splice the harness to make a 91-95 fuel pump assembly plug into the 96 body harness. You might have to swap the instrument panel too, I'm not 100% sure if 91-95 vs 96 clusters have slightly different fuel gauge guts. Or you can put the returnless rail from a 96 on your 95 motor, cap the vacuum line that used to go to the FPR, and bolt it right in. Might need the fuel line from the filter to the rail off a 96 4.0L donor, but not sure. The rail and fuel line are small enough to be cheap at a junkyard either way.

Fun fact, all the small gauges in the cluster are the same save the faces. You can use a temperature gauge for fuel, volts, etc for all Chrysler years up to 96. This 96 presently has a functioning cluster from a 91. On that note, because it had a bad speedometer from the junkyard, I put the original base model speedometer in it and added the trip odometer so the upgraded face would look right and because trip is nice for overlanding. The only difference between Chrysler clusters that I'm aware of is the difference between mechanical and electronic speedometers. Never tried to mix and match those. As for the fuel pump, I'd keep the original 96 that's in the tank and replace fuel lines as needed. I know the connector is different but I used an older pump to run the 2.5 for a while at first with a modified connector. Some rearrangement at the body harness connectors behind the kick panel may be in order depending on how far apart the years are.

Cliff notes: You can use whatever 91-01 donor you want depending on how much work you want to put in, but if you go 97 or later, or 90 or earlier, you are in for some serious pain, and if you use a 91-94 you are in for almost as much pain, so for your sanity you really should just use a 95 or ideally a 96 donor.

I'll be looking for 95/96 then, unless one doesn't come up, then I'm going 91-94, replacing the dash harness, column, rewiring the body connectors,
etc. Done that before, it's not hard.

97-01 is completely out of the question, I just don't care for those years personally.


Please pardon my lack of experience with the quote feature.

Overland said:

That's a good point, because if I found a 96 donor for the engine wiring harness, I could pull the dash to add the TCU circuit without having to undo all of those dash harness retainers that always break.

I've covered this in previous posts. While it enters the firewall, drops behind the HVAC cabinet, and goes to the TCM on the knee bolster, it doesn't connect to anything else inside the cab. I didn't know there was a difference with the 2.5 autos, but I should have known because to my knowledge they didn't come with the AW4.

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I think we're agreeing here but not sure - you don't have to pull the dash to add any TCU circuits, just pull it back through the firewall and then push the new harness through the same hole and plug it into the new TCU.

2.5 autos came with the AW4 for only a very few years - 87-90. It's an incredibly rare option, I've only even heard of a half a dozen in existence in the last ten years. go11um (iirc - guy from upper peninsula Michigan who used to be on here) had one and used to have another. MoparManiac and Dundy saw two of them sitting in a junkyard in Millis MA years ago. esennert knows where one is hiding in middle-of-nowhere ND, and I believe some of the socal guys have seen a handful of others around. That's pretty much it. It was a super rare option, and they came with 4.56 stock diffs. 86 down and 91 up 2.5 autos are Chrysler 3-speed boxes, the 86 down ones were fully hydraulic control while the 91-up ones are just a 32re or whatever (iirc) like the YJ and TJ 4cyl used, with a governor pressure sensor and solenoid to turn the previously hydraulic auto into a pseudo-electrical auto.

Overland said:

The seats are uncomfortable and I never cared for the Dodge Neon style interior. If you can suggest anything else which might be desirable for use in an early model, I'm all ears.

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I hate the 95 and later buckets, but especially the 97 and later ones. The earlier ones have those high bolsters that actually make you feel like you're sitting in a bucket seat, not on half of a bench seat someone took a chainsaw to and called it a bucket seat.

The interior I never used to like but it grew on me after all my 96-down interiors started cracking and falling apart. I'll likely swap it into my 88 at some point but that point isn't here yet.

Only stuff I'd consider swapping are... hmm. I'd keep all the driveline and suspension parts of course, and you might consider swapping the front doors if you like the newer window style vs the old two window style. If not, you can swap the mirrors alone. I like the look of the old mirrors more but it's nice to actually be able to see out of my mirrors so I swap to the larger new style ones.

Overland said:

Fun fact, all the small gauges in the cluster are the same save the faces. You can use a temperature gauge for fuel, volts, etc for all Chrysler years up to 96. This 96 presently has a functioning cluster from a 91. On that note, because it had a bad speedometer from the junkyard, I put the original base model speedometer in it and added the trip odometer so the upgraded face would look right and because trip is nice for overlanding. The only difference between Chrysler clusters that I'm aware of is the difference between mechanical and electronic speedometers. Never tried to mix and match those. As for the fuel pump, I'd keep the original 96 that's in the tank and replace fuel lines as needed. I know the connector is different but I used an older pump to run the 2.5 for a while at first with a modified connector. Some rearrangement at the body harness connectors behind the kick panel may be in order depending on how far apart the years are.

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Interesting. I figured that was true, but the 96 fuel sender has two sender wires aside from ground (IIRC... been years, I've got the FSM at home) - one for the empty warning lamp and one for the level measurement itself. So I always assumed the 96 gauge would get cranky without having both wires hooked up, and the 91-95 sender of course only has one wire for the level sender.

Not sure about the extra wire, but they all had a low fuel warning light, unless you had the basic cluster. Swapping in an old cluster in place of basic in the 96 provided a working light. I figure it's integrated with the PCB the assembly is mounted to.

Had to run outside and check to be sure I wouldn't have to make that hole for the TCU, but it's there with a plug covering it. I know it changed size and shape at some point, getting larger sometime around 90-91. There's a recess behind the HVAC cabinet where the harness fits but I'm not sure I could fish the plug and all through there. It's worth a shot.

Turns out I'm wrong - it's for the ECU, not the gauge warning lamp... it is a low fuel sense signal though!



I haven't read the section of the FSM that goes over *why* it's present, but my guess is that it's so the ECU can tell how full the tank is and determine when to run the evap purge solenoid. It's not present on 97-01 because on those years, there's a single-element fuel level sender that is wired to the ECU (so it can already see the fuel level data) which also forwards that info to the cluster via the CCD bus.

Thanks, I learned something today. Hadn't looked at this diagram since 2009-ish when I knew a lot less about XJs.

No, thank you. I always wondered myself.