Advice Needed: Internal-External Slave Cyl Swap on AX-4

[NickyV]

Well… I was collecting the parts and psyching myself up to finally tackle installing AC in my MJ. And then the clutch went out. Again.

 

So now the clutch is my priority.

 

I have been limping along by bleeding it regularly (not fun, but I guess I’m getting better at it).

 

Can someone give me a shopping list for making the internal-external slave swap? I have a 1987 2.5L AX-4.

 

I’ve seen some posts that say I just need a different bell housing plus a few more parts. So what do I need?

 

One more question. I’ve had the clutch fixed a few times by mechanics. This was before I really started researching how to do this myself.

 

I know the most recent time it was done that only the master was changed out.

If the clutch keeps going out, and even if it is leaking at the master (it is) should I assume the slave is going out as well? Maybe you can tell, but I’m just wondering if there is any way I DON’T have to drop the transmission.

 

Sigh. I know what the answer is going to be already. No way to know. I should probably replace all of it to be sure.

[89 MJ]

Some of this depends on what year external slave stuff you’re after. The 84-86 XJs were also external slave. 
 

This thread might help you a little bit if you’re interested in going the early route:

 

[ghetdjc320]

As for parts, if you don’t go with the 84-86 setup mentioned above, you’ll need an external slave bell housing, input shaft retainer, clutch fork, pivot ball with retainer clip, throw out bearing (DO NOT GET CHEAP WITH THIS ONE ), and the slave cylinder along with the line. Often times the master/slave are sold as a unit but you can purchase separately. Luk and Centric seem to have been good after market suppliers for clutch components. Go timken, precision, national or SKF for the throw out bearing. Transmission has to be removed. Just take it one bolt at a time and you’ll be done in no time . When bleeding an external slave setup, I’d recommend “reverse bleeding”. There are a few good YouTube videos regarding the process. It would probably be worth it to swap the clutch and pilot bearing as well. Luk rep-set clutch and a bronze pilot bushing normally are good values. External slave cylinders use a different line fitting than the old 7/16 inverted flare master cylinders used but can be adapted. 

[pizzaman09]

I went through this trouble on my AX-15. 

 

You say it is leaking at the master, I'd change that out before doing anything on the slave side.  

 

That said, when I was deal with clutch issues on my internal slave, it was sucking in air from somewhere.  It was easy to hop under the truck, crack the bleeder, and let it bleed for 10 seconds until no air bubbles were seen in the fluid stream.  Then I would top off the fluid. 

 

I needed a new slave cylinder and swapped to an external slave, resulting in a perfectly reliable clutch setup. 

[NickyV]

Hey @89 MJ and @ghetdjc320 — So if I am reading you both right, you are saying that there is a way to do this without swapping the bell housing, input shaft retainer and all that? But in order to do that, I need to find a working external slave cylinder on an 84-86 XJ?

 

Sorry… I’m doing this out of order. I will read the post from @eaglescout526 and hopefully that will make it clear.

 

On 5/11/2025 at 9:45 AM, 89 MJ said:

Some of this depends on what year external slave stuff you’re after. The 84-86 XJs were also external slave. 
 

This thread might help you a little bit if you’re interested in going the early route:

 

 

[NickyV]

OK. I just read it real quick. I need to take a closer look. Wonder if @eaglescout526wants to chime in.

 

Based on my initial understanding of this method, I’m a bit concerned that I would have to first FIND the parts or locate an XJ that old and pull the required components. 
 

Then they would have to work. And if they broke, I’d have to do it all over again. The point of doing this swap is so I can do a bunch of work all at once and then make my life easier down the road.

 

Not sure I want to set myself up for finding 40 year old components every time my clutch starts acting up.

 

Oh the joys of MJ ownership!

[ghetdjc320]

4 minutes ago, NickyV said:

OK. I just read it real quick. I need to take a closer look. Wonder if @eaglescout526wants to chime in.

 

Based on my initial understanding of this method, I’m a bit concerned that I would have to first FIND the parts or locate an XJ that old and pull the required components. 
 

Then they would have to work. And if they broke, I’d have to do it all over again. The point of doing this swap is so I can do a bunch of work all at once and then make my life easier down the road.

 

Not sure I want to set myself up for finding 40 year old components every time my clutch starts acting up.

 

Oh the joys of MJ ownership!

I posted the parts needed for a swap to the newer style vs the somewhat obscure (albeit intriguing) 84-86 style. You’ll need to pull the trans though regardless. But for sure swap the master if it’s leaking or giving any issues

[89 MJ]

15 minutes ago, NickyV said:

Hey @89 MJ and @ghetdjc320 — So if I am reading you both right, you are saying that there is a way to do this without swapping the bell housing, input shaft retainer and all that? But in order to do that, I need to find a working external slave cylinder on an 84-86 XJ?

Correct. I think. I’m not a 2.5L expert haha. 
 

7 minutes ago, NickyV said:

Based on my initial understanding of this method, I’m a bit concerned that I would have to first FIND the parts or locate an XJ that old and pull the required components. 
 

Then they would have to work. And if they broke, I’d have to do it all over again. The point of doing this swap is so I can do a bunch of work all at once and then make my life easier down the road.

 

Not sure I want to set myself up for finding 40 year old components every time my clutch starts acting up.

This is correct. You will need to find the parts, which can be tricky. That’s said, they don’t seem to really have any issues, so I don’t think you need to worry about much breaking. 

[ghetdjc320]

As far as I can tell, the only difference with the 84-86 swap is you can reuse your bell housing .
 

I will say though, a good internal slave cylinder normally works very well. Many vehicles use the internal design. I actually prefer it, provided that it’s a good quality unit. Should provide many years of trouble free operation and last as long as a decent clutch.

[eaglescout526]

I learned a lot with this swap on my 88. When I was looking at the digital catalog I saw that the bell house was pretty much the same on 86. So it got me thinking. I hunted down all the parts, pressed in the pivot ball on my bell house and put it all together with pleasing results. 
Oh you also need the transmission bearing retainer plate from an 84-86 as well. It might work without it but I didn’t want to tempt it. 

On my 84 I had to swap the bell for the fuel injection. There were no more pressed in pivots left and I wasn’t about to hunt that down. 84-85 bells use a detent where a ball bearing sits as the pivot. But I was able to take a later Chrysler screw in style pivot and put it into the bell where the pivot gets pressed in and I honestly haven’t had an issue at all either. 
 

 

But I’m all ears for any questions on the 84-86 external. 

[NickyV]

Hey @eaglescout526 and everyone else. I got busy with life the past couple weeks. I just sat down to do some more research. Everything I'm finding on EBay when it comes to bell housings says AX5 or AX15. But I have the four-speed. Does that matter?

 

And another question, I've learned a lot over the years, but I'm getting lost in a lot of the technical talk here. I feel confident I have the tools and capability to do this, but I'm just getting overwhelmed by figuring out what parts I should even get in the first place.

 

As for @ghetdjc320's point about an internal slave working well if it is a quality build... that has me thinking. If I have to drop the transmission anyway and I'm getting overwhelmed by trying to figure out this bell housing and additional equipment stuff, maybe I should just replace the internal slave. If I went that route, do you all have recommendations for the parts I should buy.

 

A few more observations and questions:

 

When the clutch went out most recently, I had to park the truck overnight on the side of the road and come back out and fix it there. It was not ideal. I found what appeared to be a pinhole in the hose that connects the metal portion of the clutch line (up in the engine bay) to the transmission. I put tape over it and wrapped a couple small hose clamps around it. I drove it about 20 more miles and it was starting to fail by the time I got home.

 

Once I was home, I worked on it some more. I took my time re-wrapping the location where I found the pinhole using some pipe tape and I re-tightened the hose clamps. It's been a few weeks now, and I haven't driven it very far, but every time I've gotten in the truck since then the clutch has seemed pretty good.

 

All of this to say I'm not 100% that the slave is actually leaking. It might have been that pinhole that I think I found. Maybe I should start by replacing that length of hose and the master cylinder first. I'm not entirely sure what kind of hose I should get though.

 

All the creature comfort work I've done on this truck has come pretty easy to me, but the mechanics under the hood is harder.

 

Sorry... I'm just kinda thinking out loud right now. And I know I'm going to be busy this weekend and next so I don't really have the ability to work on this thing yet. I know I can figure this out. But any more help would be appreciated. And explaining it like I'm 5 would also be helpful.

 

Thanks.

[89 MJ]

I’d start with replacing that line, like you’re thinking. 
 

The AX5 parts should work on your AX4. 

[eaglescout526]

Like Carter said the AX4 and 5 are basically the same. Just the 4 doesn’t have the 5th gear. So you’ll want an AX5 bell. That being said you shouldn’t have to swap bell houses but I do not know a damn thing about the HO 91-01 bell houses. I only know about the 84-86 set up. 

[ghetdjc320]

Swap that hydraulic line. You’ll need to just replace it from the master to the slave cylinder. Don’t try to splice it as it will not last. You’ll need to bleed out the air afterward. 

[pizzaman09]

Absolutely agree, replace the line first, that's a fairly easy job.  

 

I've found with Comanche clutches, that gravity bleeding works very well, just open the bleeder at the slave and keep toping off the fluid at the master cylinder.  Eventually close the slave bleeder and top it off one more time at the master.