Hydraulic clutch help needed

[Sluggo]

Ok. here's what I got.
CNC 305b slave
WILWOOD 3/4 inch master.

All bled out and operating. Not quite enough stroke to not grind going into reverse. I've preloaded the t/o bearing as much as I dare.

What might I be doing wrong?

[95GT]

Sounds like you just need a bit more stroke on the slave cylinder. You can try changing your mounting point on your clutch pedal or go with bigger bore on your master cylinder. One other option is to shorten your clutch fork.

[midpack]

If it's a T5, they all do that if you don't put it into a forward gear when you're at a complete stop first

[Fast68back]

If it's a T5, they all do that if you don't put it into a forward gear when you're at a complete stop first

+1, they all do it. Hit 5th gear and then reverse...

[buening]

I've read the same thing happens with the TKOs, you have to put it in 2nd before going into reverse otherwise it'll grind.  Not sure about the T5 though.

[daveSanborn]

If that's the only problem you're having Sluggo.... you don't have a problem.  Like others have said already, the reverse gear is slowly spinning on a stopped/running vehicle.  To get it to stop spinning, throw her into 5th and then back down into Reverse.

[Sluggo]

I understand the reverse concept. Tried it.

I feel like I have the t/o bearing preloaded too much. I need extra stroke on the slave, it does not even reach the end of the bore.

I have a 7/8ths master coming from Wilwood. It has a tad longer stroke and the extra fluid volume will push more fluid into the slave bore thus forcing the piston to travel further. I also do not have to change the reservoir, hunt for fittings or have to reconfigure the lines again. I just have to lose some more skin from my forearms to swap it out.

This will allow less preload and increased future adjustability. I'd be pretty pissed if I ran out of adjustment after the clutch breaks in.

I think this is sound reasoning.

Agree?

[Fast68back]

Cant you relocate the slave to give you more throw?

[Sluggo]

Cant you relocate the slave to give you more throw?

How would relocating it give it more throw?

I'd just have to shorten the rod if I moved it closer.

[johnpro]

Shift to 2nd, then to reverse.  Known problem with the TKO transmissions.

2nd and reverse share a servo.

[johnpro]

I'd be pretty pissed if I ran out of adjustment after the clutch breaks in.

How much of the clutch are you planning on burning off?  :ecit

[Sluggo]

How much of the clutch are you planning on burning off?  :ecit

Hopefully not much. I'm sure it will require adjustment at some point. If I have too much preload I assume that time would come sooner than later.

[68EFIvert]

Same problem on the T5 and TKO huh?  I have a T56 and don't. :lol  Neener neener neener. :bart  :beat  Yet another benefit of 6 forward gears.

[95GT]

How would relocating it give it more throw?

I'd just have to shorten the rod if I moved it closer.

If you move the mounting point on the clutch pedal lower it would you will get more throw on your master cylinder.

[johnpro]

Hopefully not much. I'm sure it will require adjustment at some point. If I have too much preload I assume that time would come sooner than later.

Unless you're out there smokin' the tires, you should not have ANY significant burn off of the clutch material, especially if you use a GOOD Kevlar clutch.

[Sluggo]

The throw is perfect. Actually, at first it was a little too long and pushed the piston past the fluid inlet allowing fluid to get behind the piston and leak into the cabin.

I had to make a pedal stop to prevent it from going all the way to the floor.

The problem is not that I'm not getting full stroke on the master, it's that I'm not getting full stroke on the slave. I can stroke the master until the spring inside collapses if I want to.

When speaking with Wilwood tech today he confirmed my suspicion.

3/4 inch master with 1.1 inch stroke.
7/8 slave requiring 1.25 stroke.

So a 3/4 master is only going to push the volume that exists in the cylinder. No magic there.
I don't know the formula nor do it care to look for it, but logic dictates that the volume in the master be pushed to the slave when the pedal is depressed.
If the slave had the same size bore, it would move the piston 1.1 inch. Since the slave is larger it needs more fluid than the master can deliver to stroke the same distance. Again, I don't know the math but I doubt the slave moves more than 3/4 to 7/8ths of an inch.

Now, with a master with the same size bore, 7/8ths with a 1.2 inch stroke, the master and the slave have the same size bore. The slave has no choice to move exactly the distance the master is stroked.

With a slight preload and a 1.2 stroke, I will get that little extra I need.

The guys that are running the CNC master get away with a 3/4 inch master because it (i'm told) has a 1.5 inch stroke. This is actually a better setup because the larger the bore in the master the more effort it takes to apply the clutch.

But, since I already have the Wilwood remote reservoir mounted and it's plumbed for the Wilwood, I'm sticking with the Wilwood. I really don't want to replumb it or chase down more fittings.

[buening]

That setup with the stroke and bores of the master/slave combo results in 0.81" of slave piston travel from full master bore travel.

[95GT]

So what are your plans then Sluggo? Are you going to replace the slave cylinder with one with a smaller bore?

[Fast68back]

So what are your plans then Sluggo? Are you going to replace the slave cylinder with one with a smaller bore?

The new MC will solve his issue, the bore and stroke on the MC and slave will be the same, so he will gain the needed stroke from the slave by replacing the MC with the larger bore/stroke.

[johnpro]

The throw is perfect. Actually, at first it was a little too long and pushed the piston past the fluid inlet allowing fluid to get behind the piston and leak into the cabin.

I had to make a pedal stop to prevent it from going all the way to the floor.

The problem is not that I'm not getting full stroke on the master, it's that I'm not getting full stroke on the slave. I can stroke the master until the spring inside collapses if I want to.

When speaking with Wilwood tech today he confirmed my suspicion.

3/4 inch master with 1.1 inch stroke.
7/8 slave requiring 1.25 stroke.

So a 3/4 master is only going to push the volume that exists in the cylinder. No magic there.
I don't know the formula nor do it care to look for it, but logic dictates that the volume in the master be pushed to the slave when the pedal is depressed.
If the slave had the same size bore, it would move the piston 1.1 inch. Since the slave is larger it needs more fluid than the master can deliver to stroke the same distance. Again, I don't know the math but I doubt the slave moves more than 3/4 to 7/8ths of an inch.

Now, with a master with the same size bore, 7/8ths with a 1.2 inch stroke, the master and the slave have the same size bore. The slave has no choice to move exactly the distance the master is stroked.

With a slight preload and a 1.2 stroke, I will get that little extra I need.

The guys that are running the CNC master get away with a 3/4 inch master because it (i'm told) has a 1.5 inch stroke. This is actually a better setup because the larger the bore in the master the more effort it takes to apply the clutch.

But, since I already have the Wilwood remote reservoir mounted and it's plumbed for the Wilwood, I'm sticking with the Wilwood. I really don't want to replumb it or chase down more fittings.

So now I'm thoroughly confused.  Do you have a problem now or not?  Sounds like you think you do, but only trying to get in reverse?  Have you tried shifting into another forward gear before shifting to reverse?  For most of us, this is just habit, now.

[SELLERSRODSHOP]

with the current setup, he's essentially trying to fill a quart jar with a fluid from a pint jar. with the 3/4" wilwood master, there isn't enough fluid moving thru the 7/8 slave to get a full stroke & properly acuate the clutch.

[Sluggo]

So now I'm thoroughly confused.  Do you have a problem now or not?[1]  Sounds like you think you do, but only trying to get in reverse?[2]  Have you tried shifting into another forward gear before shifting to reverse?[3]  For most of us, this is just habit, now.

1.	Yes
2.	Not the typical shrort grind, a long nasty grind
3.	Yes

I installed the 7/8ths master today and life is good now. I have the preload on the throw-out about where I'd expect it to be now. Tightened the rod until it would not spin and gave it another 1/4 turn. Clutch completely disengages and if I hit reverse without passing through 5th I get just a short, slow grind. Like others have described.

Buening's calculation is right in line with my suspicion. Which means I was around 3/8ths of an inch short on stroke. That explains the crazy preload I had to put on it.

[95GT]

Glad to hear you got this fixed Sluggo. It might just save me some headaches if I choose that way to go when I get around to my clutch set up.

[Sluggo]

Glad to hear you got this fixed Sluggo. It might just save me some headaches if I choose that way to go when I get around to my clutch set up.

If you are running power brakes on your car I would highly recommend using the CNC master. Both of the Willwoods had to be modified to fit in the limited space.

[95GT]

If you are running power brakes on your car I would highly recommend using the CNC master. Both of the Willwoods had to be modified to fit in the limited space.

I am almost thinking I am going to have to go with manual brakes on my car. After looking it over I might not have room for a booster and the tall valve covers I have. But that will be a few months down the road yet.