Hydro Clutch Slave Cylinder

I'm changing to a hydro clutch in my '68 225/T14. I've not yet found the right slave cylinder. The clutch master is 3/4" bore from Speedway. I can find 7/8" slaves all day long, I need a 3/4".

I went through the calculations and the full MC stroke (without subtracting some margin for a hard stop at the pedal) will only move a 7/8" slave piston about 0.6". It's just not enough. The clutch fork sweep with the current mechanical linkage is .75" at the connection point.

So now it looks like the Novak unit is about my only choice. Yea, it's pricey, but it is 3/4" bore and the bracket is made for the 225 jeep. It comes with a new clutch fork. And I'll assume that's to change the fork ratio so I'll need to run through those calculations too. Can I change out the clutch fork without puling the bellhousing? I don't recall as its been awhile since I put a new clutch in and I would not have used that process anyway.

Or does anybody have any other 3/4" MC & SC solutions. I've looked at lots of other vehicle parts but the fit just isn't right. I have no problems fabbing a bracket.

 

I used 1980 CJ hydraulic clutch set up.

 

Although lots of factory clutch setups are matched with both clutch and slave bore being Identical which will only get you a one to one stroke between the two being used. If you want to increase the stroke at the slave....................Best to match a larger 13/16" or 7/8" bore clutch master with a smaller 3/4" bore slave..........and yes Novak probably has the best one out there that can travel almost 2".

The fork should still be a 2 to 1 ratio where it enters the bell housing..............Make sure you still have adequate pedal to floor / firewall travel while also maintaining a 6:1 pedal ratio................you should be fine.

 

I used this setup also. I even added(welded on)length to the stock cable pull fork to be able to mount it. If you have swinging pedals I suggest going this route.

 

Speedway Motors
Part #70174
Bore size 5/8 to 1 1/8
$75




Slave
Part #91025604
7/8 bore .88 stroke
$35

 

I am fighting a slave travel problem myself currently. I had bought the 80,s set up but the master is slightly larger than the slave and just don't have enough travel. I searched forever for other slaves that would work, but the guy at the flaps came up with a 85 s-10 slave, the bore is .81 which is smaller than the master and will hopefully yield a bit more travel.. I can let you know today if it works.

 

While we're on this topic, I have the older style mechanical/hydraulic clutch assembly on my '62 CJ-5. Unlike most assemblies I have ever seen, instead of pushing on the release fork, this one pulls it. I would like to replace this with an hydraulic setup. Has anyone ever done this, and if so, what did you use as a slave cylinder? I already have a master cylinder installed in the firewall, while I am looking for a way to use it. Is there a slave cylinder made to pull on the cable instead of pushing? I understand that the Chevy Aveo was built like this, but since that car is no longer produced, parts are rare and expensive. I don't want to buy something I can't use...

Thanks in advance for any help...

 

The purple slave cylinder that rattyflatty posted above appears to be a pull cylinder.

 

The purple one looks identical (except that hideous color) to the Wilwood pull back slave I'm using. They can be had from Wilwood or Summit Racing.

Wilwood Disc Brakes - Master Cylinders: Slave Cylinder

Wilwood Disc Brakes - Master Cylinders: High Volume Master Cylinder

The MC is available up to 1" dia.

 

I installed the s10 slave yesterday and have a clutch, barely! I made a adjustable rod for it and with some adjustments and a little more bleeding, I think it will work just fine.. I definitely has a bit more travel. With my old slave, I couldn't get the throw out bearing off of the clutch fingers and still have a functioning clutch. With this slave I have all kinds of room to pull the bearing off the fingers and still able to get the clutch to disengage.

 

Yes , the purple one is a pull type and it looks like Wilwood makes them for Speedway as they are identical. That would have been easy to set up too. But since it is a 7/8" bore the one sitting on my bench will be returned. As well as the 3/4" bore Honda unit I sourced from the FLAPS. It just didn't have enough travel.

I did see the "combo" MC that Rattflatty posted. I already have a 3/4" MC. No doubt there are enough choices out there that my jeep could be up on blocks for years while I make up my mind. I'll likely go with the Novak slave as I want to preserve as much adjustment as possible.

 

If travel is what your after in your slave............you must first have a larger bore clutch master cylinder mated with a smaller bore slave............It's all about fluid transfer volume and how much area it takes up.......no other way to get there!

 

Pascal's Law.

F=PxA or P=F/A or A=F/P

F= Force
P= Pressure in lbs. per square inch
A= Area in square inches



I wish I had a better image that shows the relationship of volume vs. pressure handy but I don't have anything I can easily upload. In the image I posted the input cylinder has a pressure of 10 psi with a piston surface area of 1 inch. In the output cylinder we have a surface area of 80 square inches so have a total force of of 800 pounds. What the pic doesn't show is that if we move the input piston 8 inches we will only get 1 inch of movement from the output piston, or 1/8th the movement of the input because the output piston is 8 times the size of the input piston.

 

Yes ... it's a class-1 lever, done with fluids.

 

Thanks for the information. I will get one and get it on after I take care of some more pressing issues. Does it ever end with jeeps?
BTW, a belated Happy Vet's Day to all you vets out there. I did my 20, but I thank you all for your service, too.