If the AX15 isn't broke, should I rebuild it?

- 91 XJ
- 235,000 miles.
- Rebuilt 4.0L HO with 40k miles.
- AX15 with internal slave
- NP231 TC

Ok ... I need to pull my tranny to get at the internal slave cylinder. I'm thinking while I have it out, I should rebuild it, because I think it has 235K miles on it. It is shifting fine now and not really showing any problems, but I'm thinking "while it's out" I might as well do a full rebuild -- bearings, seals and synchros.

Here's some more info:

- I've never done a trans rebuild before and I'm kind of itching to do it as a learning experience.

- The serial number stamped on the bottom shows that it was made in November of 1990

- The tranny has a small amount red RTV sticking out between the case sections. Perhaps it's already had some work done before I bought it? Or does it come from the factory with red RTV?

- I plan on keeping this jeep forever ... at least another 10 years or so, and if the trans has high miles, I'd prefer to do it now, rather than wait for it to screw up in the future.

- If a main bearing goes bad in the future, and it's not addressed quickly, it can create more damage from the mis-aligned shafts and forks.

So ... what do you think? Should I rebuild it or not? The only thing that makes me think maybe not do the rebuild is that red RTV might mean it's already had major work done on it.

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i'm contemplating a rebuild on the one i just pulled out of my project jeep as well. mine has 282k on it and there is quite a bit of metal dust on the magnetic drain plug. I've rebuilt chevy autos before but never a manual, i hope it's easier because autos are a pain in the ass lol. I was just going to slap it in and keep going but it's going behind a stroker and will be my daily driver, so I'm a little worried about the metal in the oil.

yeah ... I forgot to mention there was some metal dust on my drain plug too.

And ... this would be a great excuse to get a hydraulic shop press!

google turns up some decent rebuild articles if you search for "ax15 rebuild forum", i won't directly link them here because they aren't on this board but maybe that will help you decide what to do on yours. :cheers:

Yeah ... thanks. :cheers:

I've found some really good writeups, a pdf file of the complete rebuild instructions, and a great video by "robinsonauto" on YouTube. I'm really psyched to do this job, but some little red flag in the back of my head says "if it ain't broke, don't break it."

Anybody know if the AX15 came with red RTV from the factory?

Since you are going to the trouble of rebuilding the transmission why not change over the slave cylinder location from inside the bellhousing to outside the bellhousing. If there is ever a leak in the slave cylinder it is easy to replace and will not damage your flex plate, clutch and pressure plate.
IIRC the change over took place some wheres around 1994.
The AX-15 in my '98 has red RTV between the sections of the transmission case and it has never been disassembled.

Hi Charles:

Thanks for the response. The reason I have to access the slave cylinder is because I had the flywheel resurfaced when I put in the new motor. Big mistake. The shop took off .080", which moves the pressure plate and disk farther from the slave cylinder throw-out. This is why they say you should never resurface the flywheel.

So ... Now the clutch doesn't fully disengage. Since the slave throw-out is farther from the pressure plate, it doesn't push it far enough to fully disengage the clutch. It's a very, very tiny amount of engagement ... you can hardly tell that the clutch isn't fully disengaged, and it shifts fine when the jeep is moving. But when the transmission is warmed up (and the fluid is thinner), and the motor is running, it's very hard to get it into first gear. When the trans oil is cold and thicker, the slight engagement of the clutch doesn't turn the transmission shafts, because they are resistant to spinning in the thick oil bath. That shows how minor the clutch engagement is

My solution is to make a shim plate to put under the slave cylinder to move it closer to the flywheel. You just have to be careful to not shim it too much, or the clutch won't fully engage!

I've thought of going through the trouble of switching to an external slave. I would *definitely* prefer an external. Can you adjust the throw action on an external slave? It seems like and PITA, and there is a significant expense also. How much would something like that cost?

Most of the Junk yards in my area don't have xjs anymore, and they also don't allow you to go in there and look around, which is disappointing.

I believe that all that is required would be the newer style bellhousing, the fork that holds the throwout bearing, and the clutch master cylinder/hose/slave cylinder assembly (comes as one assembly). Not sure what they would cost, but there are online Recycling Yards that sell Jeep parts.
You might even find the bell housing assembly on Ebay.... http://cgi.ebay.com/ebaymotors/Jeep...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
Shouldn't be more than $75......
Why not replace the flywheel instead of shimming since the transmission will be removed.....??

CharlesS said:

I believe that all that is required would be the newer style bellhousing, the fork that holds the throwout bearing, and the clutch master cylinder/hose/slave cylinder assembly (comes as one assembly).

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Doesn't it also need a new front bearing retainer for the transmission?

CharlesS said:

Not sure what they would cost, but there are online Recycling Yards that sell Jeep parts. You might even find the bell housing assembly on Ebay.... Shouldn't be more than $75......

Click to expand...

I guess the ideal thing would be to find a junk yard with a ruined ax15 to use as a donor. Then get new hydraulics.

CharlesS said:

Why not replace the flywheel instead of shimming since the transmission will be removed.....??

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Well ... I think the shimming would work just fine. The old flywheel is still in good shape, and a new one costs another $75.00. Why throw money away when there is a perfectly good solution? Another option is flywheel shims. They sell them in 0.50 and 0.25 sizes. I might do that, since it would save me from having to fab a shim for the slave cyl.

If I put in an external slave, does it have adjustable throw? That would save me from doing any shimming at all.

montanaman said:

Doesn't it also need a new front bearing retainer for the transmission?



I guess the ideal thing would be to find a junk yard with a ruined ax15 to use as a donor. Then get new hydraulics.



Well ... I think the shimming would work just fine. The old flywheel is still in good shape, and a new one costs another $75.00. Why throw money away when there is a perfectly good solution? Another option is flywheel shims. They sell them in 0.50 and 0.25 sizes. I might do that, since it would save me from having to fab a shim for the slave cyl.

If I put in an external slave, does it have adjustable throw? That would save me from doing any shimming at all.

Click to expand...

Not sure about the bearing retainer....

When I removed the external slave a few years ago to replace the throwout bearing, clutch & pressure plate; I didn't see any adjustment for throw length....

The OP question was the trans. Jeep did not use red sealant on the cases (leastways in would not have squeezed out...) so your box has been apart. For the minor costs of a small parts kit and set of syncro's, I'd freshen it up as it is out anyway. For that matter, the large bearings are not all that expensive either...

I've seen red rtv sticking out on a couple and doubt that they were rebuilt. I have a 2wd ax15 that I bought from a guy that rebuilds them in the middle of PA. I believe I destroyed at least the input shaft bearing from doing a 1.5 roll@75mph in my 94 some years back because when I tried using it in my stroker, there was noise in a couple of the gears. I do want to take it apart and fix it(about the only thing I haven't done on a jeep). I remember watching the guy use a stick magnet to take out ball bearings. Need a good pair of snap ring pliers.

So, there is nothing wrong with the AX-15 right now other than the resurfaced flywheel problem? I would not rebuild it if it's working fine now.

The AX-15 in my '92 had over 750,000 KMs (466,000 miles) and needed nothing but a couple of clutch jobs.

If you treat is right it will last a long time.

If you are worried about future availability of parts, as you say you want to run it at least another 10 years, buy a rebuild kit or a JU AX-15 now and throw them in storage 'til you need them.