Intermittent Clutch/Shift Porblems 90MJ

[Sleepydog]

I 've got a recently acquired '90 MJ 4.0 with an AX15. (150,000 miles). Runs like a top, no major problems, but every now and then I have difficulty getting it to shift (especially into 2nd and 5th).

This weekend I took it on an extended trip (4hrs) on the highway, and towards then end of the trip it didn't want to downshift at all. I was able to force it, but it left me feeling a little uneasy...

Today I'm out at lunch and I can't get it into reverse (without grinding). Once I got her going, it shifted flawlessly...

Is this just the beginning of the end for my clutch?

The fluid in the master cylinder reservoir is clean and it is full, no leaks on my feet or the fuse box...

Any advice would be appreciated.

 

[Johann]

If it has an internal slave cyl (in bellhousing) you may be experiencing the beginning of the end. Whoever designed the internal slave has a special place in hell waiting for them.

Mine acted up like that untill full out failure on a 600 mile trip. It was sucking air at the slave- not loosing fluid at all. I thought it was the master and replaced it but no luck. Managed to get home by bleeding the clutch at every gas station from PA to NC. Great fun...

Try bleeding the system to see if it cures the problem. It just might. If it returns you probably need to open it up. 150,000 is about when mine gave up. My clutch plate and all were not all the way down to the rivets but close. The slave quit first.

If you do go in I would suggest you consider swapping in an external slave system from a 95+ AX15 while you are in there. The parts are available from any decent junkyard for not too much money. Having the external slave allows you to fix this problem in the future without having to pull the tranny. I have a write up on my inststall if you want it- just pm me.


Johann

 

[MaXJohnson]

Also, check and see how close the fluid line comes to your exhaust header. Your problem sounds like it might be heat related to me. Extended driving on the freeway boils fluid so clutch doesn't fully disengage when you press the peddle. The heat can also damage the flexible part of the hose. If you have the infamous cracked header (pipe #6), this will make it even worse.

I'd try bleeding the system at the slave cylinder as Johann suggested too.

 

[Pete M]

Or it could be a low fluid level in the tranny. My old peugeot gave me shifting problems as the oil leaked and the level dropped. I'd top it off and she'd shift fine again.
Could maybe even be the synchros going south. Your tranny needs GL-3 oil and I'm betting it's got GL-5 in it like the shop manual mistakenly says. The sulphur compounds in GL-5 eventually eat away at the brass synchros. If it turns out that your clutch assembly is fine, now might be a good time to drain it and refill with the right stuff before it gets any worse.
Jeep on!
--Pete

 

[dan f.]

i had the EXACT problem Johann described. if bleeding the system temporarily cures your problem, its most likely what you have. i also converted to the external slave and couldn't be happier. a word of caution: i'm fairly certain that if you convert to the later style, you must use the clutch from the years that used the later style, check Johann's write-up, it might say. i didn't and had to get a newer one. good luck.
dan f.