Hydraulic clutch Q's

vette427sbc

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As some of you may know, I am trying to finish up my hydraulic clutch setup and I have a few questions-
What kind of fittings do the master and slave cylinders use?
Also,
I can push the rod into the slave cylinder about .5" from its neutral position- Is it supposed to be mounted with the rod pushed in from the neutral position? is that the spring that auto adjusts for clutch wear?
Pictures are on the way :cool:
 
That's a good question. The fitting on the master and slave measures .462 OD, not really sure what that would be. The bleed screw on the slave cylinder is the same thread, maybe a good parts store could match that.

Edit: I found out the fittings on the slave and master are 12mm x 1.0p. I found some 12mm to 3/16 brake line adapters at NAPA (Weatherhead PN 7936).

1/2 inch of preload on the slave should work. Make sure and get a full stroke on the truck master. You will need to push as much fluid as you can into the slave to get proper travel.

Did you reinforce the firewall where the slave mounts?
 
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I did some calculations and came up with when the master is pushed 1.125", the slave moves around .8" , and I think that is just enough to disengage the clutch.

I thought that the early c-3 firewalls were already reinforced? When I drilled the holes to mount the master, I drilled through a pretty thick piece of metal.
 
There is a plate on the inside of the car. On my car it looks like it's probably 1/16 inch thick. That might be enough to counter the force of the hydraulic cylinder, I don't know. Keep in mind that the force you feel at your foot is greatly reduced by the lever ratio of the clutch pedal, the force on the firewall is much higher.
 
Classic Chevy 5 speed didn't want to sell a hydraulic clutch with their kits for vette, they said the firewall isn't strong enough. IMO that's BS, there's indeed a metal plate in that area, it spans all the way to the top and the pedal box hangs from it too. All C3s have that plate, not just the early ones.
 
I installed a t56 lt1 transmission in my 81 corvette. With all the research I did. I used a clutch mastercylinder from a 86-87 chevy truck and used a line pressure fitting to mate it to the stock lt1 slave cylinder.

I cut and welded the actuator rod to fit the stock pedal settup exactly where the mechanical linkage would have connected. I used a small bushing to fit the actuator rod to the pedal pin, to make up for the different sizes.

Then I made sure that the actuator rod had no more than 15/16 of an inch travel and installed a clutch pedal stop on the floor.

With the 15/16 inch of travel I had no problem at all with the clutch engaging and disengaging. I was told by ATS (american touring specialties) that with any more than 15/16 travel you would damage the mastercylinder.

I used clutch master cylinder Raybestos part # cma39732 and mounted it directly to the firewall drilling through through the 1/16 steel plate.

Hope I was some help to someone out there.
 
All I can say is what ATS specialties told me. It works well on my car. Are you using the same master cylinder as I am?

ATS= www.americantouringspecialties.com they do alot of t56 swaps and customs 5 or 6 speed swaps.

WE also have to make sure that we are talking about master cylinder rod travel and not pedal travel.... two completely different things. my rod travels 15/16
 
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I was told by ATS (american touring specialties) that with any more than 15/16 travel you would damage the mastercylinder.

15/16" :confused: I have a little over 1.5" of travel on my master cylinder- should I not be using all of this travel??

That might be a problem, the truck master I have only has 1.25 inches of travel end to end. Sounds like to might be bottoming the cylinder.

jsssgrl1209, are you using the chevy truck master? What are you using for a slave?
 
That is exactly the problem..... I was told that anymore than 15/16" of travel you would bottom out in the cylinder, which will cause it to break prematurely.

AND yes, the part number I listed above is for a truck master cylinder....if I recall 86-87 chevy they pretty much are all the same (c20, blazer ect.)

My slave cylinder is the brand new stock unit from a t56 transmission. If needed I can get pics for you.

One thing I am sure of, you dont want your master cylinder to bottom out from to much rod travel!
 
Ok, I am finished with my clutch, I just need to bleed it now, but how am I supposed to know if my master is bottoming out? I've been pushing my pedal in by hand, and i can feel the cylinder just stop. It is very smooth up until this point. Is that the end of travel, or is that going too far? Its still about 1.5-1.6 inches of travel at the rod.
I am going to make a pedal stop so that it will come close to, but not bottom at this point
 
Good question

When you are pushing the rod in and it stops....that is when it is bottomed out. You need to set your pedal stop to not allow that to happen..

I installed my pedal stop on the floor so that the clutch pedal itself hits the stop before reaching the bottom of the master cylinder.

Just push the clutch in and out with your hand and you will hear the rod bottoming out in the master cylinder. I did this with the master cylinder not connected to the slave, so there was absolutely no pressure in the hydraulic line.

You want to adjust your master cylinder so the only noise you get is the sound of the clutch pedal hitting the stop.

Let us know how you make out.
 
Classic Chevy 5 speed didn't want to sell a hydraulic clutch with their kits for vette, they said the firewall isn't strong enough. IMO that's BS, there's indeed a metal plate in that area, it spans all the way to the top and the pedal box hangs from it too. All C3s have that plate, not just the early ones.

I thought I would share a picture to support your statement. I can't see any reason why that plate wouldn't be strong enough for a hydraulic clutch. The plate is definitely heavier then what a modern car firewall is made out of.
080809004.jpg
 
That is exactly the problem..... I was told that anymore than 15/16" of travel you would bottom out in the cylinder, which will cause it to break prematurely.

AND yes, the part number I listed above is for a truck master cylinder....if I recall 86-87 chevy they pretty much are all the same (c20, blazer ect.)

My slave cylinder is the brand new stock unit from a t56 transmission. If needed I can get pics for you.

One thing I am sure of, you dont want your master cylinder to bottom out from to much rod travel!

Time to wake up a thread...
jsssgrl1209,
I'll be doing a similar swap very soon. I plan on sliding in an LS1 T56 in and planned on running the truck master cylinder as well. I'm not sure if the slave cylinders are different between the LT1 and LS1 T56's, but how did you know that the slave cylinder was engaging the clutch enough?

Also, when you built in your clutch pedal stop, was the clutch pedal stopped close to the firewall or was it a few inches off? What I'm getting at is there enough master cylinder shaft in order to have the clutch pedal touch the firewall? Not sure if I made it clear or not.
 
Sorry it took so long for me to reply....thought this thread was pretty much finished.

There are many differences between the ls1 and lt1 t56 transmissions.
Major differences are that the Lt1 style uses a pull type pressure plate....as compared to the LS1 push type.

Another difference is that the slave cylinders are completely different..... The lt1 uses an external slave cylinder that mounts onto the bellhousing that pulls the pressure plate to disengage the clutch. The LS1 uses a internal slave cylinder that mounts on the input shaft of the transmission and pushes the pressure plate to disengage the clutch.

You asked " how do I know that the slave cylinder was engaging the clutch enough"........ I personally go by feel......I have driven alot of muscle cars and regular cars and it is pretty obvious if your clutch isnt disengaging enough..... you can feel it!!

The way I did my clutch pedal stop was by the following...

1.I installed the clutch master cylinder to the firewall. Obviously since I used a Truck master cylinder the rod was way too long for my corvette.

2.I made sure my pedal was all the way up and I marked exactly how much I needed to cut off the rod to make it mount to my pedal. Cut the rod n welded it back together.

3. I took a measuring tape and measure my 15/16" of travel and looked at the best loaction for the pedal stop.

4. Drilled and added a pedal stop. Here is a pic of the pedal stop to give you an idea of where I mounted it. thum_11074a971a8330fe8.jpg




And here is a pic of my custom made center console plate to accomodate for the different location of the shifter. .thum_11074a971b4e56325.jpg


I also had to customize my crossmember. I lowered it 1" so the trans will not hit the tunnel of the car and moved it forward 1 1/2".

Since I moved my crossmember forward I had to lengthen the E brake cable to complete the swap. An alternative option to this is to weld a custom mounting plate to the crossmember. That would have been alot easier, regret not doing it that way, but it worked out well for me.

If you are doing this swap be prepared for alot of customizing and alot of work. I can take pictures of anything you might have questions about.
 
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Thanks! I think I'm seeing your pedal stop in that picture. It's pretty short correct? My biggest concern is I don't want the clutch pedal stopped multiple inches off the fire wall. That would just feel odd, but if that was the way it had to be, so be it.
After I asked about the similarities between the LS1 and LT1 T56's, I did a part search and what I would find were internal slaves for the LS1 type and external slaves for the LT1 type, so I probably should have checked that first.

I plan bolting on a bracket to my crossmember for support and then cut any needed clearance for the tail housing (which I've heard I need).

I like that console plate. I'm not sure what I'm going to do about that yet. I'm still debating to make the shifter come up in the stock location or just mod the console cover.

I'm still in the very early stages of this project, but I'm sure I'll be asking more questions.

Thanks again!
 
Yes you definately need to make room for the tailshaft to the crossmember......and I am sure you will have to lower the transmission by 1".

The pedal stop is very short and make sure you use a heavy duty bolt like I did!! When I race someone I slam that clutch to the stop and let it fly back up......make sure you dont use a crappy stop. It is very important.



I dont think that you can make the shifter come up in the stock location. Here is a pic of mine. You will notice how short the hurst handle is on my PRO 5.0 shifter. The handle was cut down to 5" I think...... When the trannsmission is mounted you will find that the shifter base right under the tunnel. This makes you use a tiny shifter handle, so it looks good in the car and you can shift comfortably.

Moving the shifter over to the left is very easy, just use some 2 1/2 bolts and a spacer has worked fine in my other swap. The problem is moving the shifter forward. I dont see any easy fix for this. Hope you have an idea. thum_11074a9844ae75f9c.jpg

Since my shifter sits so far back I had to move the light switches in front of the shift boot on my custom center plate.
 
In CF there's a guy that did. He modified the shifter, not the shift stick. It required welding. I would get you a link but got to run. It's really clean so when I can, I'll edit the post and add it for you.

Edit: His name is Joe and here is a pic of his shifter from his site:
c3gs-051307a.jpg

The full website dedicated to the car:
http://vettetech.com/projects/c3gs/c3gs.htm
 
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Not sure

In CF there's a guy that did. He modified the shifter, not the shift stick. It required welding. I would get you a link but got to run. It's really clean so when I can, I'll edit the post and add it for you.

If he was using a t56 transmission this is the only thing I can think he used.

thum_11074a9882fa48d7c.jpg

The yellow arrows is where the shifter attaches to the transmission and the green circle is where the shifter attaches to the internal rail.

It is a shifter mechanism from a cadillac CTS-V. It does the following. It eliminates the use of the rearward shifter mounting location and uses a location located more upfront.

From my understanding you cant use that shifter on the lt1 or ls1 transmissions.

AND if you could use it, you would first have to buy the shifter along with the transmission mounting so you could attach it to your internal shifter rail.

Then you would have to modify your cars transmission tunnel to allow room for clearance.

I would think he used the complete transmission from the Cadillac for the swap.

If he didnt I could really kick myself in the ASS. Cant wait to see your pics GREG
 
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