My 99 TJ with the 4.0 and 5-speed will not go into gear while running. When engine is off, I can run the shifter through all the gear positions (3rd can be a little tight) but when engine is running I cannot move shifter into any gear position except revers it seems able to move to but grinds when I start to move shifter into reverse so I immediately revert to neutral. So I guess my clutch will not release. I don't notice any fluid leaks, it is a hydraulic clutch.

Looking on-line at some how-to sites about changing a clutch, I decided this job would be way over my head. And I don't even know enough to diagnose the problem --clutch or cylinders? So I had it towed to a transmission shop. I expect they'll call me this afternoon to tell me what I need. Do I trust him if he says I need a new clutch or doesn't this just sound like a master-slave cylinder problem? On the phone before I had it towed there he was saying maybe new clutch, but another shop with too long a wait list said sounds like slave or master cylinders.

So if it is cylinders, would you replace both together? Or just the one that failed. A friend advised that if one goes (say, the slave) then should also replace master because it will probably go soon after. Treat them like a unit, like we did when we put new universal joints on both ends of rear axle even though only one seemed bad?

Also, if I do need a new clutch, is it worth the extra money to get a heavy-duty clutch or is OEM good enough? On-line I found OEM clutches for about $180 and Centerforce Heavy Duty clutch (they say its 90% stronger than OEM) for about $305. And those are not necessarily the brand and prices my mechanic will offer but I cite them as probably low approximations of the price difference he'll probably offer me if I enquire about a heavy duty clutch.

I do take it off-road sometimes, through swampy mud and over rocks and steep hills. I don't know how much it affects the issue but I'll add that I have 31 x 10.50 mud tires on it and a 2" suspension lift. Except for a great LoD xtreme duty rear bumper with spare mount, the Jeep is otherwise stock.

It sounds like the clutch just needs to be bled. If it isn't leaking fluid from the slave cyl. it is probably fine. If bleeding it does nothing then perhaps the master is bad. Unless you have the internal slave (probably not), I would only replace the defective part. The guy who did your rear shaft probably got paid for both joints... Whenever I replace parts I just fix the broken one and save my time and money on the good one(s).

Normally a clutch disk wears out gradually. To suddenly loose the clutch function usually means one of the cylinders has failed or something is wrong with the linkage. I believe a fellow in the local club had major issues with his clutch after getting stuck (big time) in some gumbo mud in his TJ. I didn't pay much attention to the problem as I barely knew the guy but I believe some how he filled the bellhousing with mud and the clutch suddenly didn't work at all. Did the clutch quit while you were playing in mud? I don't believe there is anything to be gained by paying more for a HD clutch unless you are planning on drag racing. I also wouldn't change a working cylinder just because it's partner was bad. The notion that one failed is a sign the other will soon is bogus IMO. <img src="/forums/images/graemlins/cheers.gif" alt="" />

I agree with sunder and Pete. I'd like to add, the HD clutch is for an engine with extended hP! Just go with stock clutches and you will be Ok.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

Thanks to everyone for the advice. It was the slave cylinder. Running great now! But if the clutch ever goes, I'll take the advice to stick with a stock replacement.