Clutch/Slave Cylinder Issues

[YJJPWrangler]

Having issues with my clutch not releasing at all. Jeep won't go into gear/if I try to start it in gear with the clutch depressed it will rock forward.

4.3 mated to a SM420 with a hydro bellhousing

I have this slave.

https://www.summitracing.com/parts/wil-260-1333

1 3/8" throw for the slave. The master I believe is a corvette model(its been so long since I bought it, I forgot).

I have tried adjusting the linkage to resolve the issue but thats not working. I removed the shift cover boot and can see the clutch fork, throwout bearing, and pressure plate. Throwout bearing slides smoothly on the transmission input shaft. Right now, I'm getting about 1" or so of movement in the slave cylinder during cycling.

I did not bench bleed the master or the slave. I have since bled them and gotten a lot of air out of both of them. I plan on picking up a master cylinder bleed kit just to verify that all the air is out. I gravity bleed both of them and got a steady stream of bubbles for about 5 mins and then pure fluid.

Any ideas? Any advice for setting the throwout bearing/slave cylinder?

 

[NickMaul]

I believe when your fly wheel and clutch wear down you begin to have trouble getting out of gear. So maybe you have a some wrong parts or the clutch disc is installed backwards against the flywheel?


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[a_kelley]

1 3/8" throw for the slave. The master I believe is a corvette model(its been so long since I bought it, I forgot).

I'm getting about 1" or so of movement in the slave cylinder during cycling.

check the bore of the master and compare it to the bore on the original application master. I ran into that on the Toyota master and Chevy slave, the toy master didn't move enough fluid to get the slave to fully extend and release. So I used/modified the matching Chevy master to fit where the toy one was.

 

[YJJPWrangler]

Clutch is brand new. Installed correctly(literally says "flywheel side" on one side of the clutch). Flywheel has been resurfaced as well.

check the bore of the master and compare it to the bore on the original application master. I ran into that on the Toyota master and Chevy slave, the toy master didn't move enough fluid to get the slave to fully extend and release. So I used/modified the matching Chevy master to fit where the toy one was.

This is what I'm thinking, I'm not getting enough fluid to move the slave. Maybe this could work?

https://www.summitracing.com/parts/wil-260-10373

@strange1 what did you run with this setup?

 

[a_kelley]

If the bore x stroke matches the original application, it will work. Actually if the displacement volume is the same as the original it will work. (Though a bigger bore, shorter stroke will make the pedal force higher, where as a longer stroke smaller bore will lessen pedal force)

You can figure out the volume you need if you have the dimensions of the slave.. then you just figure out how much stroke you would need for a given bore size, or bore size from stroke available.

 

[Fabrik8]

I think I may have missed something here: Is this a new combination of hydraulic parts (with the previously mentioned new clutch) that is not working from the beginning, or is this an existing combination of hydraulics that has suddenly stopped working with the new clutch?

 

[YJJPWrangler]

I think I may have missed something here: Is this a new combination of hydraulic parts (with the previously mentioned new clutch) that is not working from the beginning, or is this an existing combination of hydraulics that has suddenly stopped working with the new clutch?

All new parts. Have never worked from the beginning. I'm still thinking I have air in the master/slave and thats preventing it from cycling fully.

 

[Tradarcher]

There's no chance they are rusted together is there? Has it been a while since you installed them and the time you started it?

 

[a_kelley]

So you'll lack .02 cu in of fluid from full travel.. or..
.02/.520=.038,

about 1/32 in.. which is pretty much nothing.

What's your existing master application/bore & stroke? If you can tell me that I can tell you how much it should travel as it is setup.

 

[YJJPWrangler]

There's no chance they are rusted together is there? Has it been a while since you installed them and the time you started it?

Negative. New motor has been in a month ish and has always been garaged kept.

Bled it here, and then pulled it out of the jeep because I'm suspecting that I am not getting full stroke travel because the pedal is hitting the floor. I measured and it looks like I have a 1 5/8" travel on the stroke. With the pedal, I'm getting about 1 3/8" stroke. I also bench bled it and got some really big air bubbles out of it. Looks like I'm going to have to rework my pedal to get full stroke but that shouldn't be that big of an issue.

My concern is...will that 1/2" plus air in the lines be the deciding factor in getting the clutch to release?

@a_kelley, its been so long since I bought it, I can't remember. But I do seem to remember it being a mid 80's Chevy.

 

[NickMaul]

Is your hose braided or strait rubber?


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[YJJPWrangler]

Is your hose braided or strait rubber?


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Hard line for the first foot then goes to braided steel line.

 

[Fabrik8]

Is your hose braided or strait rubber?

Doesn't generally matter for a clutch system. There's not enough hydraulic pressure or enough line length for hose expansion to become an issue for fluid volume.

 

[Fabrik8]

Negative. New motor has been in a month ish and has always been garaged kept.

Bled it here, and then pulled it out of the jeep because I'm suspecting that I am not getting full stroke travel because the pedal is hitting the floor. I measured and it looks like I have a 1 5/8" travel on the stroke. With the pedal, I'm getting about 1 3/8" stroke. I also bench bled it and got some really big air bubbles out of it. Looks like I'm going to have to rework my pedal to get full stroke but that shouldn't be that big of an issue.

My concern is...will that 1/2" plus air in the lines be the deciding factor in getting the clutch to release?

That's 1/4 inch stroke difference, not 1/2 inch (2/8 is 1/4 inch). We know what you meant though. Have you done any adjustment to the master cyl pushrod?

Yes, air in the lines can be a big issue, especially if you're already marginal for fluid volume vs. displacement.

I think that's what you really need to look into though; If you're right on the edge of everything working properly under ideal conditions because you have a very small margin of extra fluid volume, and then you chip away at that tiny margin with air bubbles and lack of pedal stroke and those other little things.......

Obviously it's very important to find out what master cyl you actually have, because you have what appears to be a volume problem (and the master cyl is half of the volume equation).

 

[YJJPWrangler]

That's 1/4 inch stroke difference, not 1/2 inch (2/8 is 1/4 inch). We know what you meant though. Have you done any adjustment to the master cyl pushrod?

Yes, air in the lines can be a big issue, especially if you're already marginal for fluid volume vs. displacement.

I think that's what you really need to look into though; If you're right on the edge of everything working properly under ideal conditions because you have a very small margin of extra fluid volume, and then you chip away at that tiny margin with air bubbles and lack of pedal stroke and those other little things.......

Obviously it's very important to find out what master cyl you actually have, because you have what appears to be a volume problem (and the master cyl is half of the volume equation).

There is no adjustment on the master cylinder pushrod. It's just a steel rod with round hole at one end for attaching to the pedal. I have thought about modifying it by cutting it in half and threading/welding some adjustment to it. The bubbles were pretty large but there were maybe 4-5 of them. No more bubbles now. I can't for the life of me remember what master cylinder it came out off.

 

[a_kelley]

Looks like a Nissan or Toyota master. I'll look up one for a 90 1500 with the nv3500 and see what the bore and stroke is, likely similar mounting to what you got.

Stroke I can't find. However the matching slave is 13/16 bore and I can measure stroke on the master if you want.

 

[YJJPWrangler]

So I reworked the pushrod and am now getting full stroke out of the master cylinder and the slave. When I hook the slave up to the clutch fork, its noticeably harder to cycle the clutch(for obvious reasons). I can just barely see the clutch fork moving as I push the pedal(due to my body position).

When I set the stroke of the clutch fork, I push the clutch fork up against the pressure plate and then adjust the slave cylinder to that. Is that the correct way to do this? Or am I adjusting it too far in? How much movement against the pressure plate is needed to disengage the clutch?

With the slave cylinder not hooked up to the clutch fork, I get full movement out of it. I'm now leaning towards the clutch fork. Some research has shown that there are two different types of forks, a cast one and a stamped one. I've also seen that there are different kinds of throwout bearings as well.

At a loss right now. All the parts I have are new and seem to be in good working order. This is the clutch I have.

https://www.napaonline.com/en/p/NCF1104902

I've also seen people suggest parking it against a tree and starting it in gear with the clutch in. Worth a shot or no?

 

[a_kelley]

Throw it on stands, put it in gear, engine off, try to spin the driveshaft with clutch depressed. That's how I test if the clutch is releasing. It should be relatively easy to turn the output/driveshaft by hand with the trans in gear when the clutch is disengaged.

 

[R Q]

Could be your pivot ball also...

 

[YJJPWrangler]

Put it up on stands. Adjusted the slave all the way out so the throwout bearing is further away from the clutch. Easier to depress clutch pedal and there is a solid click of the throwout bearing hitting the pressure plate. Tires still spin in gear with the clutch depressed. At this point, I have half a mind to drop the transmission/transfer case to see what the F is going on...

Could be your pivot ball also...

I've seen some reports of this but talking with @strange1 today he never had issues with this setup.

So I'm back to thinking something is up with the actual clutch install even though I know I installed it correctly as it had flywheel side stamped on the side of the clutch.

 

[a_kelley]

Maybe it's bound on the pilot bearing/bushing.. if you can see the clutch plate depress, that's my only other thought..

 

[YJJPWrangler]

Bringing this back up to the top. Still fighting with this. I have now switched my master out to this unit.

Wilwood Disc Brakes - Master Cylinders: High Volume Master Cylinder

The 1" bore. I have verified with Wilwood that this is more than enough to operate the slave. I have bled the slave/master countless times. I am getting full travel from the slave when it is not hooked up to the transmission. Once I hook it up to the transmission, I get almost no travel whatsoever. I can manually engage the clutch via the throwout arm with a 2x4 and a pry bar but it takes a lot of force. I am wondering if I have my slave in an optimal position. Right now it is inline with the throwout arm on the X/Y axis.

I am thinking about trying to find a regular push style slave and seeing if I can fit in in there. I have about 1.5-2" clearance from the exhaust to the stock mounting location.

 

[paradisePWoffrd]

Bringing this back up to the top. Still fighting with this. I have now switched my master out to this unit.

Wilwood Disc Brakes - Master Cylinders: High Volume Master Cylinder

The 1" bore. I have verified with Wilwood that this is more than enough to operate the slave. I have bled the slave/master countless times. I am getting full travel from the slave when it is not hooked up to the transmission. Once I hook it up to the transmission, I get almost no travel whatsoever. I can manually engage the clutch via the throwout arm with a 2x4 and a pry bar but it takes a lot of force. I am wondering if I have my slave in an optimal position. Right now it is inline with the throwout arm on the X/Y axis.

I am thinking about trying to find a regular push style slave and seeing if I can fit in in there. I have about 1.5-2" clearance from the exhaust to the stock mounting location.

When pushing on the pedal, is it too stiff to push or goes to the floor?

 

[YJJPWrangler]

When pushing on the pedal, is it too stiff to push or goes to the floor?

Too stiff to push. The slave doesn't act like it even wants to move the clutch fork. We did get the clutch fork to engage(no slave hooked up) but had to use a pry bar and a block of 2x4 to move the clutch fork. It was not easy to do.We measured the amount of travel that the clutch fork needs to travel to engage and we have plenty of travel in the slave. I have verified that the clutch is installed correctly and nothing is binding. The T/O bearing slides freely on the input shaft.

 

[paradisePWoffrd]

With the larger bore on your master, it now requires more pedal effort to move the fluid.

Assuming that there isnt something binding in the clutch making it too stiff; if that is the master you need to get the correct volume, you will need to increase the pedal ratio to get it comfortable to you.

Here is a link to the brake bible: BillaVista.com-Brake Bible Tech Article by BillaVista There is a calculator in there that might help. I know that is for brakes, but the math for hydraulics apply. If you are certain that there isnt anything mechanical incorrect in the system, the first step would be to measure the amount of force and distance required to disengage the clutch completely. Knowing that and the slave that you are using, will allow you to calculate the the master and pedal ratio needed.

Here is a video that shows you how to convert a bottle jack to a scale: . Could get a big fish scale also.