Need help: wrong throwout bearing??

[CobraV8]

I have a close ratio toploader with lakewood bellhousing in my car and had a problem with the clutch being way to stiff right from the start. I've tried several sizes master and slave cylinders without any success, now I moved the pedal assembly up and installed longer pedals for better leverage and also changed to a clutch cable. But the clutch is still very hard to engage.

Someone told me that maybe the throwout bearing could be the wrong one for the pressure plate I use. It's a diaphragm type, and I was told I might need a throw out bearing with a rounded contact face for the pressure plate, otherwise reduced leverage will be the result.

The throw out bearing I installed has a flat face where it pushes on the clutch.

Could this cause such a severe increase in clutch force? I mean I'm only 25 and have no problems with my left leg, but the car is nearly undrivable because of the stiff clutch.

Simon

[Mr.Fixit]

Your throwout bearing is not the problem.

[CobraV8]

Thats good news because I won't have to remove the transmission then.

Could this problem be caused by the clutch lever fork? The clutch fork I have is the short type that was used with a z-bar clutch linkage. Looks just like this one:




Does the z-bar setup create additional leverage? If it does then maybe a clutch fork that's intended for use with a z-bar linkage will not work with a cable, because the missing leverage will make the pedal too stiff, right?

[CobraV8]

This is a picture of my transmission before I installed it:




Maybe someone can see what's wrong with it...

[trularin]

mr. fixit is right, it's not your TO bearing.

Change the pressure plate for starters.

Just a thought.

[CobraV8]

I have already changed the pressure plate from a long style to a less aggressive diaphragm style. After that the clutch was a little less stiff then before, but the result was minimal.

Do my thoughts on the clutch fork only make sense to me or does someone else also think it could be too short for a cable setup?

[Mike Simard]

Does that clutch arm have a 1:1 pivot ratio? If you have a master and slave cylinder of the approximatley the same size, you would need an arm that had a 2:1 ratio. You want somewthing like 1 inch travel at the master cylinder to wind up as 1/2 inch of throwout bearing movement.

[CobraV8]

Mike, at first I had a master and slave cylinder of the same size. Clutch was near impossible to release.
Then I moved to a 3/4" master and a 7/8 slave. The result was only a little better, still way too stiff clutch. I even tried a 1.5" slave cylinder from a Mercedes truck with the 3/4" master, now the clutch release pressure was ok, but of course the clutch was only engaged about half when the pedal was fully depressed. I calculated it would take a 3/4" master cylinder with about 3 - 3.5" stroke to fully engage the clutch with this slave cylinder. I couldn't find something like that, besides this pedal travel would be about a mile with this long stroke master cylinder.

I tried several clutch cylinder combinations, relocated pedal assembly and installed longer clutch pedal, and changed the long style pressure plate to a less aggressive diaphragm style. And as Mr. Fixit and trularin said the throw out bearing also is not the problem.

This leaves only the clutch disc and the clutch fork. I don't know what else would cause this problem. AFAIK the clutch disk itself has no influence on clutch pedal effort.

What about the others who have toploaders in their Cobras, do you use the stock clutch fork, with cable setup or hydraulics/McLeod hydraulic TO bearing?

Did anyone else ever have a problem with the stock clutch fork? Are all toploader clutch forks the same length? Can a clutch fork that's designed to work with a z-bar linkage ever work right with a cable at all?

I really appreciate any help!!

[Bruce Edwards]

I am reading your post for the first time and just wish to be clear as to what kind of trouble you are having. The pedal is hard for you to push or the trans is hard to shift or both?
A hard pedal effort is a direct result of leverage.
Hard to shift is from a clutch not releasing or bad blockers in the toploader.
If you can give me a bit more info I will try to help.

[CobraV8]

Hi Bruce, the trans shifts perfectly, my problem is the hard pedal effort.

I think the problem I have is the clutch fork is not long enough to give the leverage that's needed because it is the stock clutch fork that was used with a z bar linkage in the 64' Fairlane.

I assume the z bar mechanism had a longer lever from the pivot to the end where the rod to the clutch pedal is attached versus the shorter lever from the pivot to where the push rod for the clutch fork is attached.

So when using this kind of clutch fork with a clutch cable the pedal is pretty hard to push.

I've come to this conclusion after I tried several master and slave cylinder combinations, relocated the pedal assembly and installed a longer clutch pedal and a clutch cable, and changed the long style pressure plate to a less aggressive diaphragm style and nothing helped.

Do you think the clutch fork (as shown above in one of my previous posts) could cause this problem? If it does, what fork could I use for this transmission?

[Bruce Edwards]

The fork is not the problem. I see in this post that you used a master and slave and you say it was still hard to push. If the master is larger than the slave or the same size the pedal will work better. The pivot point can be changed so you have more leverage. That will also make it easier to push.
I set up a 427 car with a slave from a Ford truck, this was before they became all the rage, and cut the fork off by a inch or more and welded on a flat plate to mount the pivot from the slave on. Pedal effort was not a problem but I had the master and slave all worked out for the car as well as a good lever set up at the pedal point.
What pedal set up are you using?

[CobraV8]

The pedal assembly is from a Mustang II, I recently modified the clutch pedal, it's a bit longer than stock (don't know exactly how long but I can measure it tomorrow).
I am using a clutch cable from a 88' Mustang. The point where the cable attaches to the pedal is already very close to the pivot point.

You mentioned that you welded a flat plate to the clutch fork. My clutch fork seems to be cast (64' Fairlane HP close ratio toploader). Did that cause you any problems? Or can I weld it with a mig/mag welder?

I will probably go back to the 3/4" master and 7/8" slave cylinder setup. I haven't tried this yet with the longer pedal, as I wanted to use a clutch cable.

If any possible I'll slightly elongate the clutch fork, this in conjunction with the longer pedal and the smaller master and bigger slave cylinder should result in acceptable pedal effort. At least I hope so.

[Bruce Edwards]

I think I see your problem. Did you say in this post that the cable is hooked near the pivot?? Needs to be WAY up at the top of the pedal. The leverage you are looking for is the difference between the pivot and the pedal and pivot and the cable hook up. The closer the cable is to the pivot the harder the pedal is to push.

[CobraV8]

Bruce, I'm a little confused. Maybe I got this wrong, but I think the formula for calculating leverage is:

F1 x d1=F2 x d2

The pic below shows my clutch pedal (I hope it does ).

If I assume d1 is one foot long and F2 is 100 Pound, and I want to have only 10Pound pedal effort , then d2 is calculated like this:

d2= F1 x d1/F2, in this case d2=10lbs x 1ft/100lbs=0.1ft

So the closer the cable is attached to the pivot the easier it is to push...or am I completely dumb ? As far as I understand the closer it's attached to the pivot the more pedal travel is necessary.

Please tell me if I'm wrong or kind of stupid-I can take it as long as I find a solution for my clutch problem

[Bruce Edwards]

Ok maybe I did not say what I wanted to the correct way. My concern is the if you have the cable set to close to the pivot you will not have enough movement of the cable AND it may be causing a binding at the cable due to the way it is trying to pull the cable.
I guess I could have asked my question better and come up with a better way to try to help.
You are correct in that the longer the pedal is from the pivot the less force you need to move it.
If you have tried both a master/slave system and a cable system and both are hard to push it has to be the way the pivot is set up or a drag on the bearing.
If you get a moment call me so I can get a better handle on what is going on. I will be in the shop till 5:00.
407-857-8587 I may have an idea or two still but I want to ask you some questions.

[CobraV8]

No problem at all Bruce! I'm glad you try to help me as I can use some help with this problem.
I think I also explained the changes I made to the pedal assembly the wrong way.

When I tried the different master and slave cylinders I still had the shorter pedal. This winter I decided to remove the hydraulic cylinders in favour of a relocated pedal assembly with longer clutch pedal and a clutch cable. I hoped to get enough leverage from the longer pedal so it would work better with the cable than it did with the hydraulic cylinders before (I also had some leakage problems and got sick of the hydraulic stuff).
In fact clutch effort decreased with the longer pedal and the cable, but it's still so much it bends the pedal.

My thoughts were as follows:
1. installing a longer clutch fork (or modify the old one) to get additional leverage and keep the cable in place. Anyway I don't know if this will be enough.

2. re-install the 3/4" master and the7/8" slave cylinder with the longer pedal, and maybe weld a piece of steel to the outer end of the clutch fork to move the point outwards where the slave cylinder rod pushes on the clutch fork. With the big slave cylinder and the additional leverage of the modified clutch fork I hope to get the result I want.

As far as the phone call is concerned I'm sorry but I'm located in the south of Germany near Munich, and a call to the USA would be pretty expensive. Anyway thanks a lot!! I really appreciate your help!

Simon

[Bruce Edwards]

Ouch I can see why you would not wish to call.
Some things to look at.
Check to be sure the pedal shaft is not binding and the bushings are in good shape. A lot of the old Mustang II set ups are worn out and the pedal moves to one side as it is pushed and binds.
The fork you show is set up for a push system not a pull system. So one thing that may help is using a late model fork and moving the pivot to the other side of the bell. Look at a T-5 set up to see what I am talking about.
I would go the other way on the clutch set up if go back to a master/slave set. Use a larger master and smaller slave. The larger master will give you more fluid to push the slave and thus the clutch rod. The 427 car we did some time ago with a slave set up we used the standard fork cut the end off and welded on a flat plate to hook up the clutch rod off of the slave. The slave was bolted to the block so it did not have much leverage but it worked smoothly and with little effort.
If you are bending the pedal you have a BIG problem No way should it be that hard to push.
I wish I could talk to you and get more info about how it is all set up but I would not want to call Germany either!