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Discussion Starter #1
I have a 1988 YJ Sahara V6 Manual Trans. that I acquired a few months ago. Since then I've been having a heck of a time getting the transmission and clutch reliable. As far as I can tell it looks to be the AX15. I noticed a small leak coming from the clutch bell housing and and also noticed that 1st and 2nd gear were a bit clunky. I took it in to have the leak repaired thinking the fluid is low and should be a quick fix once the leak is stopped. However we noticed that the drip was actually looking more like engine oil seeping into the housing, which they felt came from a worn out hydraulic clutch slave. Replaced that, a worn out clutch disc, and also the differential seal which was leaking a bit as well.

Thought the issue was fixed. But within a matter of days it felt just as clunky, if not worse, and the leak continued. Brought it back and they felt the slave was somehow wrong so replaced it with another slightly different one, did the bleed job and sent me on my way again.

Leak still continued and after a few weeks the clutch had started to show signs of serious issues. 1st and 2nd would sometimes be near impossible to get into. The clutch pedal was losing the distance at which it engaged. Pumping did nothing, an occasional restart of the engine would mend the issue for a few minutes. After a few days of fighting it, finally the clutch was simply gone, no hydraulic pressure, a brick. Had to tow it to the shop.

They're diagnosis: redo the bleed job. It seemed to have worked for a bit, but now, once again, after a couple weeks, Im recognizing the signs of the clutch slowly deteriorating. And of couse, the leak continues. It's most noticeable when the engine has been on for while, hot days, etc. During a 90mile road trip, it starts to loose reliability about halfway and it nerve wrecking getting to the destination. Not knowing if Ill be able to get into gear once I hit traffic. Also, there is a distinct sharp tiny rattle, most noticeable in 5th gear at 75mph and over. Sounds almost like tiny rocks knocking around in there, or what I'm guessing is a worn bearing.

So... Im bringing it to a jeep specific mechanic to get his diagnosis, even though I feel the previous guys that worked on it should really try to make it right. But after 3 attempts and still dealing with it, I feel they arent the right ones for the job, unfortunately. As nice as they are were for not charging me every time I came back.

My question: Is this signs of a transmission that is in need of rebuilding, or could it be something more simple? i.e Wrong transmission fluid weight or a leak in the hydraulic line... What could explain oil in the transmission housing and causing this pesky leak? I'm over spending time and money fixing one component here and there without results. I could be into just swapping it out for a rebuilt one that maybe even has some better synchro rings etc. Any other transmissions out there that maybe would be an easy and cheap-ish upgrade from OEM?

Thanks in advance.
 

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Welcome to the Forum nikopiko,

You probably meant to say I6 engine.

If the shop stated that it's engine oil seeping onto the clutch the most likely culprit is a leaking Rear Main Seal. If you're lucky it could be a valve cover gasket that allowing the motor oil to run down the back of the engine, imitating a RMS leak or a pan gasket leak.

My guess is that if what you see leaking isn't engine oil then it's probably brake fluid. Do you check your master cylinder reservoir often, and if you do, do you need to add brake fluid?

It seems that all the original equipment clutch slave cylinders have been sold and used. That leaves aftermarket slave cylinders as the only available parts. It seems that many of the aftermarket slave cylinders suffer from poor quality control.
Talk to the shop foreman about which brand of slave cylinder they used. Other posters here might be able to recommend a quality brand of slave cylinder.
The ultimate fix is to convert your internal slave cylinder to the 1994-1995 external slave cylinder. Early TJ's may have the correct external slave setup that's compatible with the YJ platform.

If you aren't loosing brake fluid, your issue may be with the master cylinder.
In order for us to help you, you'll need to check your brake master cylinder daily and let us know if it needs topping off often.

Keep us posted.

Good Luck, L.M.
 
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Discussion Starter #3
@Luckymac. Indeed I meant I6 :) You are 100% right.

Really appreciate the insight! Clutch Master Cylinder level is showing full when turned off. It's been about 2 weeks since the last time they bled the system. I'll keep checking on it. But you mentioned, "If you aren't losing brake fluid, your issue may be with the master cylinder." Can you elaborate?

I don't think we looked at the main seal. Looks like that could easily be it too, so thanks for that!

I've captured the drip on some white cardboard in the past and it really does look like oil, possibly mixed with transmission fluid. I didn't mention it in my first post, but I actually also replaced the valve cover gasket at the same time as the transmission work since it has a small bit of oil seeping out. Looks like they did a good job, but I'll give it a good look over. regardless, you bring up a good point. I will check around to see if I can see any oil leaking from elsewhere and try to determine if my leak is coming from an external source. Oil is definitely low after only about 2K miles.

Thanks again.
 

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She's running pretty good now. Replaced the clutch master cylinder and the shifting issues went away. Also replaced the rear main seal to see if that would fix that pesky oil leak coming from the the transmission. Unfortunately it didnt do much. My Jeep guy explained that with the mopar fuel injection conversion on this motor, the resulting higher oil pressures will simply always allow for some oil to find a way to escape. The rear main seal simply isn't hearty enough to withstand the pressure from the conversion. So Ive accepted defeat and will just deal with a small leak for as long as I have this engine. Its not enough of a leak to really worry about. I'm simply checking the oil every so often and making sure the levels are good. So far havent noticed any kind of severe oil loss. At best maybe a half quart is lost between oil changes. Thanks for the help
 

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My Jeep guy explained that with the mopar fuel injection conversion on this motor, the resulting higher oil pressures will simply always allow for some oil to find a way to escape.
I'd ask the "Jeep guy" how does a fuel injection conversion affect oil pressure. My stock oil pressure gauge reads 60# pressure at highway speeds and my RMS doesn't leak. I'm running a stock carb, but I don't see how a FI conversion can have anything to do with a RMS leak.

Let us know what he says.

Good Luck, L.M.
 

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Your Jeep guy is telling you a bunch of BS! The fuel injection has nothing to do with oil pressure.
 

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Hmmmm, well crap. Then the mystery continues. Only thing I can think of is maybe it's escaping somewhere else that I can't see/access and dripping down. But I've searched high and low for that prospect with no success. It definitely seems to be coming from inside the bell housing. Thus the rear main seal seemed a likely culprit and also replaced the clutch slave cylinder for good measure. But so far, it continues.

My oil pressure seems normal although it varies between 30 and 70ish depending on how much Im pushing the engine.

If anyone has any other ideas, I'd love to hear them.

I actually noticed a new issue with my shifter/transmission last night: It seems to be an issue only after an extended drive i.e. freeway for more than 20minutes. Im not that familiar with the internal workings or the jargon for the transmission assembly, so pardon my vague description here, but basically the “springiness,” that tension if you will, which automatically centers the shifter when out of gear (in neutral) disappears. It becomes sort of rough and clunky (for lack of better words) and slides around freely when out of gear, which doesn't feel like a good thing. Can still get it into gear but it just feels off. But then after she cools, it's back to normal once I fire her up again. Could it be transmission fluid being low? I haven't been able to check yet. Im hoping its a simple thing.

Thanks, once again!
 

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I'm having a similar problem... Were you able to resolve your issue?

I found I had a shift column seat totally disintegrated in the shift housing...(photo attached) It's a quick fix... Don't know if it will solve my problem... As I'm waiting for parts as I write this...

I just had to replace my transfer case and clutch... Also found a very small master cylinder leak (waiting for part) so once both installed I'll have a better idea if I've solved my problem.

Hoping to narrow my search further with others successes...
 

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