Clutch Linkage Pedal Height Disappearing?

I’ve posed this question a couple times in other threads but haven’t gotten a definitive answer.
After the epic fail with my hydraulic setup I have since reverted back to the mechanical linkage in hopes of actually making it work. We have added heim joints on both ends of the bellcrank(rod attachment to the pedal is still ball and socket type). And corrected the angles of the bellcrank to nearly perpendicular and horizontal.

My big problem is is that we will get the pedal freeplay correctly adjusted and have a smooth and well operating pedal which will work good within the first 5 miles or so of driving. And then the pedal will get more difficult to push and lose the smoothness. And the pedal freeplay will go from a half inch to an inch or more. Thus causing the clutch to not fully disengage and become difficult to shift(crunching into first+reverse and hard shifting). But after it sits for a while the pedal play and smoothness returns to normal. All of the brackets are tightened and I have a little over an 1/8 inch of play in the bellcrank. We have had this problem ever since we rebuilt the linkage(about 8 months)



What the hell could be causing this? I am at a loss.

 

The only things that would change with heat or pressure (your two variables) are anything rubber or spring-loaded. Metal ends or linkage parts that stretch or move aren’t going to return to their previous state when they cool down or are at rest.

So list the parts that are rubber or spring-loaded that could possibly affect the pedal function:
Motor/trans mounts
Body mounts
Pressure plate
(Anything else? I’m not really familiar with the intermediate clutch linkages.)

The pressure plate is unlikely to have these symptoms, but just to rule it out - how’s its condition? Was that replaced when you changed the linkage? If not, and it didn’t do this with it in there before, you can cross it off the list.

My theory is the motor mounts are allowing the drivetrain to be pulled forward or rearward under the pedal pressure. As the mounts get hot, they get softer, allowing the rubber to move more, and they lose their form. They spring back in place when it’s parked and they cool when no longer under any pressure.

Warm it up and have someone push the clutch while you watch the engine in relation to the frame. Does it move front/back with pedal pressure? If so, I’d try some new motor mounts and see if that helps.

 

I would install a engine stay cable.

 

Motor and transmission mounts are new(within a year of being replaced) and both are polyurethane units although I am not 100% sure on the motor mounts because I cannot remember where I got them and I have had parts in the past that were claimed to be poly but ended up being rubber.

The previous owner claimed he did the clutch(3-4 years ago) and we hadn’t had these problems before.

There is a bit of body flex going on which I am working on a bracket from the body to the frame to help that. Although it looks like a bit of it is coming from the the pedal box.

Maybe my return spring that attaches onto the clutch fork is the problem? We tried using the correct spring from Crown but that fell apart after a while. We reinstalled the spring that was on there before(not sure where it came from)
What spring should I use?

It looks like there is a little bit of rearward flex on the clutch fork when I press in the clutch. Is this normal? Is there any way I could go about reinforcing the fork so it doesn’t flex?

 

Whats that?

 

A cable between the bellhousing and the frame so the motor can’t move opposite the clutch.

 

Okay cool I’ll look into it

 

Could you mount a GoPro under there looking at the linkage? Start the camera, drive around until the problem occurs, then look at the video at the beginning of the drive and at the end to see if anything looks different?

 

Oh what I could do is just take off the inspection plate on the floor and look at it while I’m driving

 

This didn’t prove anything to me.

I adjusted the clutch up a little more in hopes of when it does lose the height it won’t be as bad. Seems to work although the pedal got stiffer and I am getting an occasional bind from the bellcrank(which makes no sense to me)

 

I wonder if it isn't in the replacement clutch...

 

I didn’t want to go there but that was what I was thinking

 

I wouldn't argue that the clutch could be the problem but it wasn't 8 months ago when you started replacing your mechanical clutch linkage. Or, I should say you didn't say the clutch itself was malfunctioning. Yon noted the new mounting plate at the bellhousing became loose. Tim asked which bellhousing you have to determine correct mounting plate needed and you didn't know. Have you identified it yet? You tried a hydraulic clutch. Because your headers interfered with the placement of the slave cylinder, you welded a bracket to the clutch fork which put the clutch geometry out of alignment and caused the fork to twist. Both Rattyflatty and Ozfin suggested a pull type slave cylinder and provided pictures on how it was installed. This keeps the clutch mechanism in alignment. Did you ever try this? What was the "epic hydraulic clutch failure"? Now you are back to the mechanical clutch with the same issues that started 8 months ago.
Personally, I would do the hydraulic clutch. Because of the issues that the headers caused when trying to install the push slave cylinder, I would do either fix the header or do the pull type cylinder.

 

We have the mount to the bellhousing tightened up and shimmed out to correct the bellcrank angle. Although there is a little bit of flex in it when you apply the clutch.

I did not look into the pull type slave cylinder

I was planning on getting a set of headers that would clear the slave cylinder. My fear is is that I will have the same symptoms with my hydraulic clutch as I am having now.

Any word on the clutch fork bending rearward when I apply the clutch?

I am just trying to make the mechanical linkage work and be drivable until I can figure out how to put the hydraulic linkage in

 

This is what leads me to the bad pressure plate or driven disk issue.

 

Being that it requires so much pressure that it is bending the fork?

This is the only vehicle that I have driven with mechanical linkage so I am not %100 sure on how heavy it should feel

 

or something is binding in there

 

Because at times after really messing around with the linkage the pedal pressure will be super easy and after driving it it will return to being alot harder

 

I would try spraying some lube in there on the bearing retainer shaft for the throwout bearing. It's worth a try..

 

What kind of lube?