94XJ donor for 87MJ questions

[streetjeep2.5]

We own both a 94XJ 4.0 4x2 auto trans, and an 87MJ 2.5 4x2 4speed. The XJ we bought new and has been such a good car, my wife dearly loved it cuz it fit her well, it now has 260,000 on it, and we need to get a different "family" car because to see our daughters and grand kids we have to drive 6 hours one way. My MJ has no PS, no AC, and living in Missouri, it would be nice to have at least the AC.

Because we have loved the XJ, I would like to make its power train the power train for the MJ, and so a part of the XJ lives on in our life. I know I will need to take all the electronics for the XJ and put them in the MJ, so here are some preliminary questions:

1. I recently added a gauge dash to my MJ that was made for the 87 year. With all the electronics for the 94 in the 87, and if I use the 94 gauge sending units for the oil, temp, etc. will the gauges work correctly? I know I will need to readjust the potentiometer for the 4.0.

2. I will want to keep it a standard transmission, preferably a 5 speed. Any speedo cable issues at the transmission end when it comes to it being an 87 speedo cable?

3. And, what suggestions for a transmission, and do you know of any issues I will have with the clutch working properly, such as should I get the clutch master and slave cylinder from the 5 speed donor vehicle? What years will fit the 94 4.0?

4. I will probably put the whole front axle from the 94XJ under the 87MJ since I am going to do power steering. I like the short turning radius of the 94 due to the wheels tilting compared to them not doing so on the 87. Or, can I just change out the steering knuckles and brakes?

5. I will, of course, use the radiator and support and all other stuff under the hood of the 94 for the 87. Can you think of any other issues?

6. Finally, the rear axle. I will swap, but would it be better to find a 4.0 MJ rear axle since there would need to be modifications?

 

Ok, guys, what can ya'all help me with!

 

Thanks in advance!

[64 Cheyenne]

You'll need to swap the gauge cluster from the XJ into the MJ. One is Renix the other is HO.

Rearend shouldn't need to be swapped.Should be able to swap F/axle.

No speedo cable anymore,just needs electronic sending unit since your swapping to HO cluster and wiring.

Transmission,AX-15 2wd.(why not convert to 4x4 while your at it,your gonna be half way there) Long as you get all the same components-flywheel,clutch,slave,MC from a HO,you'll be fine.When I did my conversion I got a flywheel from a HO,It looked different from the Renix one so I didn't use it.

Don't forget to get the clutch and brake pedals from the donor vehicle also.

You won't need to be readjusting a potentiometer cause you won't have one any more,it'll be all electronic.

FWIW just be aware that to do this swap you'll have to (mark my words) swap over EVERYTHING

from the XJ over to the MJ.

[streetjeep2.5]

You'll need to swap the gauge cluster from the XJ into the MJ. One is Renix the other is HO.

Rearend shouldn't need to be swapped.Should be able to swap F/axle.

No speedo cable anymore,just needs electronic sending unit since your swapping to HO cluster and wiring.

Transmission,AX-15 2wd.(why not convert to 4x4 while your at it,your gonna be half way there) Long as you get all the same components-flywheel,clutch,slave,MC from a HO,you'll be fine.When I did my conversion I got a flywheel from a HO,It looked different from the Renix one so I didn't use it.

Don't forget to get the clutch and brake pedals from the donor vehicle also.

You won't need to be readjusting a potentiometer cause you won't have one any more,it'll be all electronic.

FWIW just be aware that to do this swap you'll have to (mark my words) swap over EVERYTHING

from the XJ over to the MJ.

 

Thanks!

1. Afraid of that IRT gauge cluster. I will have to get a later one since XJ does not have gauge cluster.

2. IRT Rear Diff; MJ is a 35. Should go 44 w/4.0, shouldn't I?

3. My 94 XJ has a speedo cable (its an Auto Trans). Whatcha mean electronic?

3. Yep, kinda figured AX15.

4. Nope, not gonna go 4WD. Thanks anyway!

5. My MJ is a standard. Won't those pedals work with an AX15?

6. Yep, kinda figured EVERYTHING under the hood IRT to engine would need to come over.

[Eagle]

Thanks!

1. Afraid of that IRT gauge cluster. I will have to get a later one since XJ does not have gauge cluster.

The biggest issue is that the fuel gauge reads backwards on the 91+ models unless you change to a '91+ sender ... or retain the pre-91 gauge cluster.

 

2. IRT Rear Diff; MJ is a 35. Should go 44 w/4.0, shouldn't I?

Why? Sure, a D44 would be nice, but my '88 XJ with Dana 35 has been wheeled all over the northeast, currently has 285,000 miles on it, and is my daily driver. All on the original D35.

 

3. My 94 XJ has a speedo cable (its an Auto Trans). Whatcha mean electronic?

Whaddaya mean speedo cable? If you XJ has a mechanical speedometer with a cable, either it isn't a '94 or it has been monkeyed with. Chrysler changed to using electronic speedometers effective with the 91 model year.

 

5. My MJ is a standard. Won't those pedals work with an AX15?

Yes, they will.

 

6. Yep, kinda figured EVERYTHING under the hood IRT to engine would need to come over.

Everything under the hood, but don't go nuts. Remember -- Chrysler sells (or used to sell) through the Performance Catalog a kit to convert the old, carbureted 4.2L Wranglers to MPFI. The kit was essentially the ECU, intake manifold, injection rail and wiring from a '94 Wrangler 4.0L. Which means the engine harness can used as a stand-alone in an older vehicle if you pay attention to what you're doing.

[streetjeep2.5]

Thanks! My D35 is doing well, so if I am "nice", it should do fine behind the 4.0? And, my 94 4.0 4x2 with an automatic does have a speedo cable, (at least what looks like a speedo cable, and comes loose like a speedo cable when I checked for a possible leak there, and has a square end to fit in the gear is attached to the tranny) and I did buy it brand new, and no one has changed anything so the tranny is still original except for fluid changing, and has never been out of the XJ, so I am not sure of the whole electronic thing, unless the cable went to something electronic that transferred signals to the speedometer.

My 87 is throttle body injected, not carbed. The 94 is multi-port. Based on your speaking IRT a 4.2 carbed to MPFI, I would think I could transfer the computer, etc of the 94, and all the harness, and be ok?

[64 Cheyenne]

the 94 should have a speedo sending unit in the usual location on the tranny,it even has a gear on the end of it to drive the electronic pickup.Then you have a "cable",actually wires,that plug into the sending unit on the trans.

You should be fine with the D35 as long as it hasn't been abused IE: burnouts,extreme towing,etc.

I think what Eagle is saying,is that you could possibly swap in a "stand alone" engine harness into the MJ,instead of the stuff from the XJ,allowing you to use the XJ HO motor without all the HO body stuff.

[streetjeep2.5]

the 94 should have a speedo sending unit in the usual location on the tranny,it even has a gear on the end of it to drive the electronic pickup.Then you have a "cable",actually wires,that plug into the sending unit on the trans.

You should be fine with the D35 as long as it hasn't been abused IE: burnouts,extreme towing,etc.

I think what Eagle is saying,is that you could possibly swap in a "stand alone" engine harness into the MJ,instead of the stuff from the XJ,allowing you to use the XJ HO motor without all the HO body stuff.

 

I will check out the speedo cable in the morning. Won't get home from the office till about 10 tonight. No noise from the D35, so I think it should do fine. I will check out the stand alone harness. Any suggestions as to where to get one? Is Chrysler Performance the only supplier of such things?

[mvusse]

My MJ has a D35, 4.0/auto, 33" tires.

 

Yes, I'm asking for trouble with the 33s, but so far it has survived 6 wheeling trips (including this afternoon for a few hours) on the 33s, and three more before that on 29s. It will soon depart. Gotta get going on that 8.25, as the brake shoes are shot again, and no more warranty on them. 3 sets of brake shoes in 4 months. Sand/gravel and drum brakes don't mix well.

 

But I'm going off on a tangent here.

 

Either way, a D35 will be fine behind a 4.0. Just be nice to it.

[Geonovast]

Out of the 5 D35s I've run, the only one I've actually managed to kill was the one behind my only 4 cylinder I've ever owned.

 

The D35 will certainly be fine for a stocker, but if you get a good deal on something else 8.25, 8.8, D44, whatever, I definitely wouldn't turn it down and get it in there.

[64 Cheyenne]

Since I have more time than money,Myself,I would do the whole HO swap.

You got the donor vehicle,put it next to the MJ,gut the MJ,swap over all from the XJ.

Bing Bang Boom,Done! Just had to say that,As I know the swap is very involved.

Very doable as others on CC have done this swap,use the search.

[Eagle]

I will check out the stand alone harness. Any suggestions as to where to get one? Is Chrysler Performance the only supplier of such things?

HESCO can sell you one, but you won't want to pay for it.

 

The point of what I wrote is that the '94 engine harness can be used as a stand-alone, without changing over the entire chassis wiring harness. All Chrysler did with the 4.2L conversions was take the engine harness part and leave out the chassis harness parts. Get a '94 XJ wiring diagram.

[streetjeep2.5]

I will check out the stand alone harness. Any suggestions as to where to get one? Is Chrysler Performance the only supplier of such things?

HESCO can sell you one, but you won't want to pay for it.

 

The point of what I wrote is that the '94 engine harness can be used as a stand-alone, without changing over the entire chassis wiring harness. All Chrysler did with the 4.2L conversions was take the engine harness part and leave out the chassis harness parts. Get a '94 XJ wiring diagram.

 

I wanna go back to the 1960's when it wasn't this tough!!! :mad:

Seriously, thanks, guys. I will do some contemplating. I would like the power of the 4.0 and the ability to have AC, etc, since this is my daily driver (all highway stuff and thus the reason for it staying 4x2).

Just thunk of sumptin'; I would probably need to use the front springs from the cherokee also, right?

[64 Cheyenne]

Springs-either or,shouldn't matter,same type suspension set-up.