drivetrain swap...2wd to 4wd

[1974CJ5]

I have a 1987 MJ 2.5 ax4 2wd (d35 rear 3.55 gears) w/ rebuilt motor, and 130,000 miles on everything else.

 

I also have a 1985 xj 4x4 with a problematic motor, the xj has: 2.5 a904 np207 d35r/d30f (4.11 gears). (only 70,000 miles)

 

So I am planning on taking the axles and tranny and tcase from the xj and putting them all in my truck. Is there any fitment issues since the firewall was moved between the years of these vehicles?

 

I am under the assumption that:

The transmission will bolt up, as I know of no bolt changes from 85 to 87.

The front driveshaft will work, as the distances should all be similar to the from xj to mj.

The axles should basically be a direct swap, and I will keep the xj's brakes, as the front brakes will not swap from the 2wd front axle to 4wd front axle.

Am I right so far?

 

I am not sure about:

Exhaust routing, looks like it will work, but looks and does are many times different.

The MJ only had 904's in 86, so the firewall moved in 87, and the np207 was dropped somewhere in there, so I am not sure if any 4x4 mj rear drive shaft will work. Will I have to have one built?

Also, will the tranny/tcase mounts swap from xj to mj of these years?

Should I take the xj's suspension parts? They look like the same ride height, not sure if the rear parts are the same anyway.

Will there be any steering issues? Will I need to rob the xj's steering components?

 

The mj being manual (ax4) and going to automatic, I know there is some engine to transmission brackes to attach to the 2.5 in the mj (a long rod, that I am unsure of the function of ((not an auto guy))). Is there any electrical parts that control the 904 that needs to be brought over?

 

This may be a lot more complex than I am thinking it is going to be. Would it be worth the money to just switch to an 4x4 version of an ax5? (i would rather not, if possible, as I have the 904)

 

A little off topic, but related. The front axle on the xj is a vacuum disconnect axle, is their any mpg advantage to not just shimming it to be engaged all the time?

 

Not that I am expecting an answer to every question, just if someone happens to know, and can help, I would really appreciate it. If this will work, I may try to do a write up w/ pictures if it would beneficial to others...

 

If I can get this to work, I can stop lusting after new compact 4x4 trucks, and save some money!

 

Also note: not terribly concerned with the strength of these parts as the truck is a garbage truck first and for-most and there aren't any rocks to climb to get to the dump. So I am not terrible interested it a stronger rear axle or tcase or tranny, for the purpose of increased durability off road.

[86customanche]

Your exhaust will probably have to be custom made unless the old MJ exhaust isnt ruined.

Rear drive shaft: depending on ride height you may have to get a new one. I personally took a shaft from a longbed and shortened it to the exact length I needed, only about 70 bucks and havent have a problem with it.

All of the front suspension parts will bolt right up, rear parts are completely different. Leaf springs are longer for MJs.

The front axle vacuum, some people will say there is a difference but it would be very very little if any IMO so go ahead and shim it to avoid any problems with the vacuum.

[1974CJ5]

Your exhaust will probably have to be custom made unless the old MJ exhaust isnt ruined.

Old MJ exhaust is in pretty good shape, so I hope it won't run into anything during the swap.

Rear drive shaft: depending on ride height you may have to get a new one. I personally took a shaft from a longbed and shortened it to the exact length I needed, only about 70 bucks and havent have a problem with it.

Hadn't thought of that, good call!

All of the front suspension parts will bolt right up, rear parts are completely different. Leaf springs are longer for MJs.

The axles should be a direct swap though right?

The front axle vacuum, some people will say there is a difference but it would be very very little if any IMO so go ahead and shim it to avoid any problems with the vacuum.

thats kinda my thought as well, but as for now one vote for shimming.

[freakjeep93]

you will need to move the spring perceh to the width of the mj spring perch

[1974CJ5]

you will need to move the spring perceh to the width of the mj spring perch

Posted: Mon Apr 23, 2012 3:46 pm

 

:fs1: could the guts be swapped, because my welding looks like chicken poo, and holds almost as well.

[freakjeep93]

probably but thats out of my leugue. i don't know squat in a diff lol

you will need to move the spring perceh to the width of the mj spring perch

Posted: Mon Apr 23, 2012 3:46 pm

 

:fs1: could the guts be swapped, because my welding looks like chicken poo, and holds almost as well.

[Jeep Driver]

What's the condition of your MJ?

[Jeep Driver]

Never mind the above question..........

 

 

Here's what you do-

 

Since I'm just down the road from ya you sell me your XJ for $500. Sell your MJ for $1800. You dig in your pocket for $200.

 

Now you got $2500 to buy yourself an already 4x4 MJ, you can git yerself a nice one too.

 

 

 

I have no trouble driving sticks or problematics. :)

[Jeep Driver]

http://charlottesville.craigslist.org/c ... 57019.html

 

 

OK, $3K.

[Pete M]

you will need to move the spring perceh to the width of the mj spring perch

Posted: Mon Apr 23, 2012 3:46 pm

 

:fs1: could the guts be swapped, because my welding looks like chicken poo, and holds almost as well.

 

 

swapping the gears is not a simple (or cheap) job. it's infinitely easier to tack weld new perches where you need them on the XJ axle and then take the axle to a shop for final welding. any muffler joint should be able to take care of it for ya. :thumbsup:

[1974CJ5]

Crap, I thought maybe I could just take both axles to "my jeep guy" and have him swap em for me for cheap, doesn't sound like it would be cheap from what you say. Thanks for the reply. Pete do you have any other insight on the myriad of questions ive posed in the OP?Would you use a mig or a stick welder on the spring perches? I have friends who can weld.

[Pete M]

unless you really want an auto, I'd skip that and hunt down a 4wd AX-5. the 904 isn't exactly desirable. it'll fit fine though.

 

you can use any welder to burn on perches. the bigger, the better, but in the end it's about as easy as it gets. I do recommend stitching an inch at a time and moving around so as to minimize any chance of warping from heat. :thumbsup:

 

the 207 will work fine as long as it's in good shape.

 

the CAD is worthless and should be shimmed for sure.

 

I had my 2wd shaft shortened locally for like 40 bucks.

 

steering parts are all interchangeable.

 

be sure to align everything after you're done swapping things around.

[1974CJ5]

I have thought about using an ax5 but my reasons for wanting the 904 are:

 

It works, I already have it, I was going to use the truck to tow around a couple atvs ( it is to my understanding that automatics increase tow rating a bit) also automatics are just easier to use when towing in my experience. ( I do prefer sticks tho) and its only got 70k miles on it.

 

Is the 904 such a dog that it's crappiness out weighs all things above?

 

Also do you see enough benefit in me making a write up on this swap that it would be worth the effort?

[Pete M]

a possible hiccup I can see is the later EFI 2.5 needs a flywheel with the cps notches, but the earlier 904 needs the torque converter stuff. not sure if it'll bolt together or, if not, what part you'll need for the hybrid. maybe AW-4 parts will work? or maybe not. :dunno:

 

there's a reason that the 2.5L/auto eventually died out. it was so gutless that jeep put its deepest gears ever in it (87+though, not 84-86), 4.56s. also, I don't believe it has an overdrive. but it might work for what you want. a couple ATVs shouldn't weigh all that much as long as they are on a light-weight trailer. also be aware that the stock bumpers aren't rated for much. and if the bumper is at all rusty, it shouldn't be used for towing.

[Geonovast]

Didn't they use the 904 in 86 behind the 2.5? Should be able to get a CPS style flex plate from that.

[1974CJ5]

On yeah! For some reason I always think that Renix Tbi started in 87, but it was 86! So I can source that from xj's so I'll actually maybe find one. Would the CPs from a manual be any different from the auto's CPs? Basically all I know about the CPs Is that it plays a role in ignition timing, and I had to put it back in when I rebuilt the motor a while back.

 

Also is the 85 904's electronically controlled at all? Because I don't want to get into a wiring nightmare!

 

I think I will move forward with the 904 if possible, and keep the things close by to go ax5 if I hate it.

[Geonovast]

AFAIK none of the 904s were electronic. I can't be sure though.

 

The CPS itself is the same. However, the CPS is a magnetic sensor that detects cutouts in the ring gear on the flywheel. If a vehicle doesn't use a CPS, the flywheel won't have what the CPS needs.

 

Another issue is whether or not the 904 you have even has the cutout for the sensor. It would be near the top of the bellhousing, on the driver's side.

[Pete M]

Didn't they use the 904 in 86 behind the 2.5? Should be able to get a CPS style flex plate from that.

 

good catch! :bowdown:

[mvusse]

Was the 904 not also used behind the 2.5 in Wranglers up through at least 94?

[1974CJ5]

So assuming I get this flex plate and all is good, how hard it is going to be to make the hole for the cps. I tried to see if my 904 had the cut out, but I can't get back there to see for all the :mad: vacuum lines. I am 99.9% sure it doesn't. If my memory serves the cps cutout is only about a half inch wide, and 1.5 to 2 inches long, but getting the positioning right scares me... The AX5 is sounding better all the time... :wall: Especially since I think if I use an ax5 I can just source a drive shaft from a junked that has the ax5/np207 set up.

[Geonovast]

If I were in your position, I would find a 4wd AX-5/231. I think it's going to be much less of a headache. Your 904 not having the CPS window is kind of a dealbreaker.

 

You'll probably need a T-case with whatever AX-5 you find, IIRC the 904 has a 23 spline output, so your 207 wouldn't be able to bolt up to the 21 spline AX-5.

[Jeep Driver]

I was somewhat teasing you before but I'm not now.

 

 

What you need is a dead 94+ XJ. You'll have a no-CAD axle and external slave and linkages....etc...

 

You will eventually find one for $500 and after you rape it and scrap it the swap is a wash, IOWs will cost you near nothing. With exception of new parts of choice of coarse.

 

 

Otherwise you are wasting your time.

 

 

As for the 85 2.5? I'm always looking for an older 2.5, I wasn't teasing about that.

 

 

The auto in your truck? dog, and you'll regret it.

[1974CJ5]

Well folks thanks for all the help. I was only considering this swap because I already had the parts and at first glance didn't seem like that much of a ordeal, and I was willing to deal with an under powered auto 4x4 mj, just for the perceived cheapness, and the increase in functionality.

 

Since it is going to cost much more than I had hoped, I think I will begin trying to source a chevy 350, sm465, np241 for the mj.

as for the 85 2.5? I'm always looking for an older 2.5, I wasn't teasing about that.

 

I appreciate that you would offer me 500 for the xj, but the interior is so super clean, and the vehicle so low mileage I think I could beat that price by parting it out or simply by fixing it, by quite a bit, and I know that means a lot of work, but I am not afraid of a lot of work. So thank you anyway.