Slave Cylinder upgrade recommendations?

[Gator Overland]

Hi all, I'm sharing my experience with clutch issues, as it seems many of us are encountering similar symptoms with varying mileage, some with stock clutch, some with centerforce upgrades, some with ACT upgrades. Reflecting on this has made me question if I should have addressed my shifting symptoms/quirks earlier.

Background

• About two years ago, I collaborated with ACT and they installed their JP6 clutch + ProMass combo after 62k miles on the factory clutch (which showed 50% wear and was on par for mileage).
• They did extensive testing of my OEM clutch as well as multiple installations tests with their clutch to show efficiency improvments dry and with grease and compared it to the OEM clutch tests to reveal a significant improvment in overall efficiency.
• The new clutch drastically improved pedal feel and engagement, eliminating the mushy and vague feeling of the factory clutch. Since then, I’ve driven 30k miles, including off-road adventures and towing, with excellent performance overall.

Symptoms
However, over time, I’ve noticed:

1. Occasionally needing to shift into 2nd before 1st gear.
2. Notchy shifts between gears, feeling resistance rather than smooth transitions.
3. Recently, difficulty getting into 1st and Reverse, especially when stationary.
   • At times, the vehicle creeps forward even with the clutch fully depressed.
   • Difficulty pulling out of 1st gear, despite the pedal being fully pressed.
4. No noticeable change in pedal firmness or engagement/disengagement distance (there may be instances that it feels as though im pushing the pedal through packing peanuts)
5. No groaning or screeching noises, all operation seems normal

Observations and Diagnosis

• The clutch master cylinder reservoir was at the MIN line.
• Visual inspection revealed:
  • Dry connections between the reservoir and clutch master cylinder.
  • Dry hydraulic line from the clutch master cylinder to the slave cylinder.
  • Residual oil around the slave cylinder (SC) flange and bellhousing. (see photo)

This indicates a potential leak causing incomplete clutch disengagement or retraction. Comparing this to their ACT Jeep Gladiator install video where they used my truck (see photo), the oil residue is a recent development after 30k miles of use (92k miles total operation).

Plan of Action

Due to the holidays, correspondance with Dirk/ACT is limited, but they are typically very involved in resolving issues via forums and facebook groups. Thankfully I’ve sourced a replacement SC in Houston. My next steps are:

1. Inspect the Existing SC:
   • Remove the SC and check for visible oil on the plunger or internal parts (a clear sign of a leak).
2. Bleed the Pedal:
   • If no oil is visible, I’ll perform a pedal bleed to rule out air in the hydraulic line.
3. Replace and Bleed:
   • If oil is present, I’ll replace the SC, bleed the system, and test functionality.

Based on threads I've read, many of you report similar issues shortly after clutch install (@Jeremynolan94 @LatteSipper @ski-line900 @BHank0688 or even after replacing hydraulic components (@SadRobot) , so my confidence in resolving this issue with a part replacement is cautious. Nonetheless, I’ll document every step of this process, as detailed information on JL/JT SC or master cylinder replacement is scarce.

(photo below shows residue leak at SC flange and dampness around bellhousing casting)

(photo below was at the time of clutch install @ ACT in April 2023. NO oil residue visible)

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[SadRobot]

Hi all, I'm sharing my experience with clutch issues, as it seems many of us are encountering similar symptoms with varying mileage, some with stock clutch, some with centerforce upgrades, some with ACT upgrades. Reflecting on this has made me question if I should have addressed my shifting symptoms/quirks earlier.

Background

• About two years ago, I collaborated with ACT and they installed their JP6 clutch + ProMass combo after 62k miles on the factory clutch (which showed 50% wear and was on par for mileage).
• They did extensive testing of my OEM clutch as well as multiple installations tests with their clutch to show efficiency improvments dry and with grease and compared it to the OEM clutch tests to reveal a significant improvment in overall efficiency.
• The new clutch drastically improved pedal feel and engagement, eliminating the mushy and vague feeling of the factory clutch. Since then, I’ve driven 30k miles, including off-road adventures and towing, with excellent performance overall.

Symptoms
However, over time, I’ve noticed:

1. Occasionally needing to shift into 2nd before 1st gear.
2. Notchy shifts between gears, feeling resistance rather than smooth transitions.
3. Recently, difficulty getting into 1st and Reverse, especially when stationary.
   • At times, the vehicle creeps forward even with the clutch fully depressed.
   • Difficulty pulling out of 1st gear, despite the pedal being fully pressed.
4. No noticeable change in pedal firmness or engagement/disengagement distance.

Observations and Diagnosis

• The clutch master cylinder reservoir was at the MIN line.
• Visual inspection revealed:
  • Dry connections between the reservoir and clutch master cylinder.
  • Dry hydraulic line from the clutch master cylinder to the slave cylinder.
  • Residual oil around the slave cylinder (SC) flange and bellhousing. (see photo)

This indicates a potential leak causing incomplete clutch disengagement or retraction. Comparing this to their ACT Jeep Gladiator install video where they used my truck (see photo), the oil residue is a recent development after 30k miles of use (92k miles total operation).

Plan of Action

Due to the holidays, correspondance with Dirk/ACT is limited, but they are typically very involved in resolving issues via forums and facebook groups. Thankfully I’ve sourced a replacement SC in Houston. My next steps are:

1. Inspect the Existing SC:
   • Remove the SC and check for visible oil on the plunger or internal parts (a clear sign of a leak).
2. Bleed the Pedal:
   • If no oil is visible, I’ll perform a pedal bleed to rule out air in the hydraulic line.
3. Replace and Bleed:
   • If oil is present, I’ll replace the SC, bleed the system, and test functionality.

Based on threads I've read, many of you report similar issues shortly after clutch install or even after replacing hydraulic components (@SadRobot) , so my confidence in resolving this issue with a part replacement is cautious. Nonetheless, I’ll document every step of this process, as detailed information on JL/JT SC or master cylinder replacement is scarce.

(photo below shows residue leak at SC flange and dampness around bellhousing casting)

(photo below was at the time of clutch install @ ACT in April 2023. NO oil residue visible)

Welcome to the party. I'm very interested in the outcome of your slave cylinder replacement and if your bleed process is successful.

 

[fczabala]

this makes me wanna buy a replacement master and slave with new hydraulic lines, centerforce has a kit that includes all these for a factory replacement, with the lines being steel braided,
@SadRobot, the new salve/master and lines you put in were sourced at a dealer? plastic/rubber correct?

 

[Jeremynolan94]

Hi all, I'm sharing my experience with clutch issues, as it seems many of us are encountering similar symptoms with varying mileage, some with stock clutch, some with centerforce upgrades, some with ACT upgrades. Reflecting on this has made me question if I should have addressed my shifting symptoms/quirks earlier.

Background

• About two years ago, I collaborated with ACT and they installed their JP6 clutch + ProMass combo after 62k miles on the factory clutch (which showed 50% wear and was on par for mileage).
• They did extensive testing of my OEM clutch as well as multiple installations tests with their clutch to show efficiency improvments dry and with grease and compared it to the OEM clutch tests to reveal a significant improvment in overall efficiency.
• The new clutch drastically improved pedal feel and engagement, eliminating the mushy and vague feeling of the factory clutch. Since then, I’ve driven 30k miles, including off-road adventures and towing, with excellent performance overall.

Symptoms
However, over time, I’ve noticed:

1. Occasionally needing to shift into 2nd before 1st gear.
2. Notchy shifts between gears, feeling resistance rather than smooth transitions.
3. Recently, difficulty getting into 1st and Reverse, especially when stationary.
   • At times, the vehicle creeps forward even with the clutch fully depressed.
   • Difficulty pulling out of 1st gear, despite the pedal being fully pressed.
4. No noticeable change in pedal firmness or engagement/disengagement distance (there may be instances that it feels as though im pushing the pedal through packing peanuts)
5. No groaning or screeching noises, all operation seems normal

Observations and Diagnosis

• The clutch master cylinder reservoir was at the MIN line.
• Visual inspection revealed:
  • Dry connections between the reservoir and clutch master cylinder.
  • Dry hydraulic line from the clutch master cylinder to the slave cylinder.
  • Residual oil around the slave cylinder (SC) flange and bellhousing. (see photo)

This indicates a potential leak causing incomplete clutch disengagement or retraction. Comparing this to their ACT Jeep Gladiator install video where they used my truck (see photo), the oil residue is a recent development after 30k miles of use (92k miles total operation).

Plan of Action

Due to the holidays, correspondance with Dirk/ACT is limited, but they are typically very involved in resolving issues via forums and facebook groups. Thankfully I’ve sourced a replacement SC in Houston. My next steps are:

1. Inspect the Existing SC:
   • Remove the SC and check for visible oil on the plunger or internal parts (a clear sign of a leak).
2. Bleed the Pedal:
   • If no oil is visible, I’ll perform a pedal bleed to rule out air in the hydraulic line.
3. Replace and Bleed:
   • If oil is present, I’ll replace the SC, bleed the system, and test functionality.

Based on threads I've read, many of you report similar issues shortly after clutch install (@Jeremynolan94 @LatteSipper @ski-line900 @BHank0688 or even after replacing hydraulic components (@SadRobot) , so my confidence in resolving this issue with a part replacement is cautious. Nonetheless, I’ll document every step of this process, as detailed information on JL/JT SC or master cylinder replacement is scarce.

(photo below shows residue leak at SC flange and dampness around bellhousing casting)

(photo below was at the time of clutch install @ ACT in April 2023. NO oil residue visible)

Thanks for your input, I'm also eager to hear what you find.

While driving last night I noticed some occasional difficulty getting into 5th gear which I did not previously have. I'm hoping it's not a sign of things to come. I also noticed that, if I am in neutral with my foot off the clutch and I attempt to push into first gear without actuating the clutch, my car creeps forward slowly as though it is in gear. I'm not sure if that is indicative of anything not disengaging fully.

 

[SadRobot]

this makes me wanna buy a replacement master and slave with new hydraulic lines, centerforce has a kit that includes all these for a factory replacement, with the lines being steel braided,
@SadRobot, the new salve/master and lines you put in were sourced at a dealer? plastic/rubber correct?

I believe the Centerforce kit is based off the JK. Yes the new line is braided. Both the cylinders are stock cylinders. As you can see below the slave cylinder has an added metal tip on the end.

This can break just like the JL. Here are some pictures sent to me by someone who has the CFII and the rod snapped.

Here you can see how the added metal tip just goes onto the end of the OEM plastic:

My replacement slave cylinder was purchased at a dealer in Dallas, Texas. My replacement master cylinder was purchased at a dealer in Buena Vista, CA. The new hydraulic line was purchased at a dealer in Downtown LA. All replacement parts are OEM and brand new. It's been suggested to me that maybe my replacement slave cylinder was defective from factory. I'm about to rule that out as I have a 3rd slave cylinder getting installed. I guess it's possible but 3 slave cylinders from factory all failing upon install seems very unlikely to me. I mean I've been pretty unlucky with this Jeep but even I'm not that unlucky.

The connections from the line to the cylinders to the CFII are also same as stock. Here is a close up of my connector that turned out to be the source of the leak. The o-ring looked fine after inspecting it but after replacing the whole line and that connector my leak stopped.

 

[SadRobot]

Thanks for your input, I'm also eager to hear what you find.

While driving last night I noticed some occasional difficulty getting into 5th gear which I did not previously have. I'm hoping it's not a sign of things to come. I also noticed that, if I am in neutral with my foot off the clutch and I attempt to push into first gear without actuating the clutch, my car creeps forward slowly as though it is in gear. I'm not sure if that is indicative of anything not disengaging fully.

Ooof, sorry to hear that. How many miles do you have on it now? I think you got your installed about a month after mine, correct?

Curious if you sprung a leak somewhere like many of us have.

 

[Gator Overland]

Thanks for your input, I'm also eager to hear what you find.

While driving last night I noticed some occasional difficulty getting into 5th gear which I did not previously have. I'm hoping it's not a sign of things to come. I also noticed that, if I am in neutral with my foot off the clutch and I attempt to push into first gear without actuating the clutch, my car creeps forward slowly as though it is in gear. I'm not sure if that is indicative of anything not disengaging fully.

If youre creeping forward without your foot on the clutch, and try to engage a gear that is normal operation. With synchros unless you were rolling down an incline at speed you probably wouldn't be able to achieve the desired gear engagement without making fantastic noises and/or stalling. Inversely, if your foot is depressed on the pedal (disengaging the clutch) and you're creeping forward when trying to put into gear, and/or having a hard time pulling out of gear, that is a sign that your slave plunger/clutch fork/and or diaphragm is not fully disengaging and some of the rotational input is minutely engaged to the input shaft (which is what im experiencing). in my experience of the issue, its not enough to even show an RPM change or make a noise.. its just a silent creep that is overcome by the slightest brake pressure.

 

[Jeremynolan94]

Ooof, sorry to hear that. How many miles do you have on it now? I think you got your installed about a month after mine, correct?

Curious if you sprung a leak somewhere like many of us have.

I have to pull out my paperwork to see at what mileage I had it installed, but it was only in October of this year so it can't be more than a few thousand. I'm going to take a look in a bit and see if there is any visible leaking.

 

[SadRobot]

I have to pull out my paperwork to see at what mileage I had it installed, but it was only in October of this year so it can't be more than a few thousand. I'm going to take a look in a bit and see if there is any visible leaking.

Keep us posted. I think I've posted this before but mine was leaking right here. It was more of a "weeping" like @Gator Overland has on the outside of his bell housing. The plastic on the underside of the master cylinder connector appeared darker. Then I felt along the line just below and my finger had brake fluid on it.

I had hoped the leak was the source of all my problems but I'm now 34 days into this with no end in sight.

 

[Gator Overland]

I posted a few weeks back about shifting issues in 1st and Reverse. I isolated the issue to a bad slave cylinder. If you’re having issues, it could be related to a hydraulic part or air in the line. I haven’t had any gear lockout issues in 600miles since install. Here’s my “how to” for replacement and bleeding.

 

[Jeremynolan94]

I posted a few weeks back about shifting issues in 1st and Reverse. I isolated the issue to a bad slave cylinder. If you’re having issues, it could be related to a hydraulic part or air in the line. I haven’t had any gear lockout issues in 600miles since install. Here’s my “how to” for replacement and bleeding.

This is a very thorough video, thank you! I might have to try the vacuum bleeding from the master cylinder to see if that helps with my pedal creaking. At roughly the 11 minute mark in your video you show the squeaking sound your pedal was making; coukd you also feel that in your pedal?

 

[Gator Overland]

This is a very thorough video, thank you! I might have to try the vacuum bleeding from the master cylinder to see if that helps with my pedal creaking. At roughly the 11 minute mark in your video you show the squeaking sound your pedal was making; coukd you also feel that in your pedal?

Thanks! As there were no other videos like it for JL/JT I felt obligated to do a thorough “how to” to pay it forward. Yes, I could definitely feel the resonation in the pedal associated with the sound when pressing the pedal before getting most/all of the air out of the hydraulic line. Smooth as silk now.

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