I recently inherited a 96 XJ Sport that I am updating for my son. We are ready to dive in and make it his own!

130k towed miles, 30k driven. It was only driven on highways, no off road or towing any loads. Jeep had been sitting in a garage for 6 yrs. Engine runs great and drives great for the first 30 minutes.

Problem : After it is warm (30 minutes), shifting is nearly impossible. Clutch pedal feels strong, but I can't shift.

Symptoms are:
1. Cannot shift into any gear. Cannot even get it to "grind".
2. If engine is off, shifting is possible.
3. After engine is off and jeep is put into gear, start engine with clutch depressed and proceed as normal in that gear, No issues.

Had tranny flushed and filled about 50 miles ago. Problem still exists. I'm sure its not Redline or Syncromesh, which I will do if I can eliminate some other issue.

Before I go to the shop and they say I need a $1500 rebuild, I'd like to understand other potential options. Ideas?

 

Sounds like a clutch or hydraulic system problem.

 

Man im not a professional transmission tech, but hopefully you did not ruin the syncros in the transmission because of the fluid change. I know they can be sensitive with the liquid change.

Other the liquid i could only think the shifter part that connects into the transmission has a plastic boot on it, maybe that got ruined? I can see that being messed up and giving you problems.

i have an 87 and i only use the Redline for that reason. Let us know what it turns out to be.

 

Stiffness in the clutch pedal like when someone says it "feels good" means nothing other than there is pressure in the hydraulic system. I had a Civic that had a great feeling pedal but had a smooth clutch disc and 5 fingers broke off the pressure plate. Not to be preachy or anything I'm just saying.

Your problem might be fixed with a new slave cylinder and a good system bleed. It really sounds like a pressure plate/slave/hydro problem to me

 

I'm guessing pressure plate is bad. If it's the original clutch, over 100k of towing is a lot. Sitting is never good. Here's the key question --- Does it feel like it's releasing the clutch when you push down the pedal after warm?? If Yes, it's likely the synchros, if No, it's likely the pressure plate.

I lean pressure plate because most people find they have WORSE trouble with synchros when cold than they do when hot.

I'd start with a new clutch set. Once you have the transmission off you'll have a better idea of whether it's the plate or not.

If you do decide there's an issue with the hydraulic mechanism, you can get a pre-bled clutch master and slave assembly for a fair price. I'd go that route since bleeding the clutch is reportedly a real PITA.

 

I'm guessing it's not related to the fluid change since the O.P. mentions, the problem "remains" indicating it was present prior to the fluid change.

Do you have an AX15 in yours? IIRC the AX15 was 89-99 originally.

O.P.
I also will only run the Redline MT90 in my AX15. If you don't know what's in it, I'd change it out.

 

You can run 10w30 or 15w40 motor oil in the AX15 as well. I used 15w40 in mine and it shifted great.

 

Sounds similar to when the hydraulic master/slave cylinder system failed in my Jeep. The replacement is pure genius, already purged, just unbolt and remove the old one, install the new one. If I had a lift, or the right jacks, I am sure I could have done it myself after I saw it get replaced at a shop.

 

Yea i have an AX-15. was originally the Peugeot BA10/5 transmission

 

Nice! Does it use the internal or external style slave cylinder? Did it bolt right up or did you have to do modifications to make it happen?

 

Unfortunately at the time its an internal slave cylinder... i want to replace it to an external though, had to change the clutch out already and was a pain with the internal. And it was basically a bolt on... do not remember having any kinds of problem, just make sure you have everything for the AX-15 ( bell housing,etc...)

 

Took it for another drive to test a few suggestions:

1. Drives great, while in gear, even after getting hot. Can even start in 2nd with no hesitation.
2. Once the problem occurs, I shut off the engine, depress the clutch and it goes smoothly into gear , start the jeep and drive away. No issues. I don't "think" its the pressure plate.

With the engine off, does that change any hydraulic pressure from the clutch? I can't figure out why it would work fine with the engine off, but cannot shift with the engine on after its hot. Hoping for one of you experts point out something I'm missing.

Goal is to build this up over the next year, with a 3" inch lift, new tires/rims and other cool stuff for my son!

 

There should be zero difference between running and not running with the clutch hydraulic pressure. It's a self contained system (hence the ability to buy the pre-bled master/slave assembly).

So let's consider what is going on in general:
1 - When the engine is on, the flywheel is spinning. When it's off, the flywheel is not. The disc grabs onto the flywheel and the pressure plate is bolted to the flywheel - when the clutch is not depressed the transmission is locked to the engine, so the input shaft is spinning at the same rate, when the clutch is pushed in, the transmission is disconnected from the engine, so the input shaft is possibly spinning (if you're moving) but might not be (the vehicle is stopped).
2 - What happens when things heat up? Metal expands. Metal can become more pliable. Fluids can thin. We know that hydraulic fluid looses it's ability to hold pressure when it becomes too hot.
3 - The way the transmission is designed, when the transmission input shaft is spinning at a certain rate of speed, it sort of locks out the ability to shift into a gear that's not consistent with that speed - hence the synchronizing of the input shaft, engine speed, output shaft.
4 - Manual transmissions are extremely difficult to shift if the clutch is not depressed while moving. It is possible, but risks damage to the transmission. They are easily shifted regardless of clutch when the engine is not running.

So let's consider your situation:
1 - Engine running and not a lot of heat present. Shifting is normal.
2 - Engine running and lots of heat present. Shifting is impaired.
3 - Engine stopped with or without heat present. Shifting is normal.

I think it's safe to assume that it's extremely unlikely to be:
- Worn or damaged synchros. This would be something that would cause problems at all times and likely isolated to a subset of gears.
- Issues with the transmission fluid. This would cause issues at all times and make shifting difficult in all conditions.
- Air in the clutch hydraulic line. This would cause problems with all clutch operation regardless of temperature.

So combining the general and specific considerations - it's possible that:
1 - The heat from the engine is causing poor quality or incorrect fluid in the clutch to fail to disengage the disc from the flywheel. That would cause difficulty shifting while moving, but allow shifting when stopped/engine off.
2 - The heat from the engine is causing the fingers on the pressure plate to not press firmly enough to release the disc from the flywheel. Again, that would cause difficulty shifting when moving but allow shifting when stopped/engine off.

So it's most probably an issue with the hydraulics and relationship with disengaging the disc.

If it were me, I'd approach it by:
1 - Seeing about bleeding all the hydraulic fluid out so that new, known correct fluid was in the master/slave system. I don't know how difficult this is as I've never had to do it.
2 - Replace the master/slave system with the full, pre-bled assembly. This is not overly expensive, relatively easy to do and not a ton of time. It is worth it to fire the parts cannon on this one if there's any chance of avoiding #3.
3 - If the problem remains, pull the tranny and put a new clutch set on it. (New pilot bearing, throw-out bearing, disc and pressure plate. I'd also replace the pivot clip for the fork.) This is a lot of work and there are a couple potential trouble spots (upper tranny bolts, aligning the transmission to re-install). It's certainly a job that anyone that is comfortable with turning wrenches can do, but it does require a serviceable floor jack and jack stands, some sort of transmission jack, a good 3+ feet of socket extensions and the inverse torx socket. A slide hammer with pilot bearing puller is helpful and can be borrowed as a loaner tool. Having a helper is also strongly recommended. If you can have the Jeep "in the garage" for at least a weekend (2 weekends and the week in between is even better) then it's a great learning experience and will save a LOT of money over having it done at a shop.

 

I'd check everything from your throw-out bearing to what has been mentioned above.... Fortunately on a manual trans... changing all of that out even if you had broken spines/fingers is not that bad of a DIY job...it's just time consuming.

 

It's VERY time consuming - and requires specialized equipment to do safely. I did find the dedicated HF tranny jack to be pretty good - definitely better than the "mounted to your floor jack" style and considering the savings by DIY clutch replacement, was an easy buy at ~130-ish (with coupons).

My gut feeling is that it's going to take a full clutch job to correct - but if it were me, it would definitely be worth it to do a new master/slave pre-bled assembly first...

When I first got my 95, between the TOB bearing growling at me every time my foot was on the clutch and the incorrect spacer plate between the tranny and engine (leaving a large section of the flywheel completely naked..), pulling the tranny was inevitable. I didn't look forward to doing it - but I got it done and the clutch and tranny have been working perfectly ever since.
If I have to do it again, I'm going to at least attempt to remove the transfer case first. The off-center weight distribution made aligning the tranny to mate with the engine very painful on both that last job and the one time I did the clutch on my old TJ.