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clutch pedal stuck on floor
#1
So my clutch pedal ('73 with a tremec T5) got stuck on the floor two nights ago, at a red light...panic set in and fortunately a guy stopped and pushed me off the road. I tied a piece of romex wire (he had in his truck) to the clutch pedal and drove home. (could pull the romex wire if the clutch pedal got stuck down again. I had just completed putting new bushings/felt washers etc. in both ends of my z bar so I figured I should take a good look for anything obvious. While observing and thinking, I figured that the z bar arm, closest to the frame, which has the clutch rod cottered pinned to it could use some assistance being pulled down. This was while I was under the car (up on jackstands) and the clutch pedal was in the "stuck down" position against the floor. When the pedal is stuck down to the floor this z bar arm is in it's "up" position. That was when I noticed the unused hole in the arm (just above the hole that the clutch rod (which passes through the floor) attaches to and a hole in the adjacent frame that seemed too coincidental. I searched through my shop's spring collection and found an appropriate one in both length and gauge. (luckily I had a few that could work) Drove the car and the problem is gone. Then I was reading the forum about this yesterday and copy/pasted someone's pic of the diagram above. Pretty funny how I came upon this diagram after figuring it out. I added some red text and circles for clarification Why has no one above referred to this "pull" spring, in the diagram, above? Everyone seems to be referring to the large diameter, heavy gauge, over the center, push? spring located behind the tach. I'm thinking, both are needed? Why not?

.jpg   Clutch Linkage - RETURN SPRING.jpg (Size: 86.49 KB / Downloads: 194)

Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic! thumb

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#2
I believe I have both on my car. When the temps rise above freezing I'll check because you have me wondering. Oh negative 7 degrees today and I've got to dig out the garage door. Winter sucks.

Going fast is fun but life is short so slow down and enjoy the ride Big Grin Frank
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#3
EBSTANG;215406 Wrote:So my clutch pedal ('73 with a tremec T5) got stuck on the floor two nights ago, at a red light...panic set in and fortunately a guy stopped and pushed me off the road. I tied a piece of romex wire (he had in his truck) to the clutch pedal and drove home. (could pull the romex wire if the clutch pedal got stuck down again. I had just completed putting new bushings/felt washers etc. in both ends of my z bar so I figured I should take a good look for anything obvious. While observing and thinking, I figured that the z bar arm, closest to the frame, which has the clutch rod cottered pinned to it could use some assistance being pulled down. This was while I was under the car (up on jackstands) and the clutch pedal was in the "stuck down" position against the floor. When the pedal is stuck down to the floor this z bar arm is in it's "up" position. That was when I noticed the unused hole in the arm (just above the hole that the clutch rod (which passes through the floor) attaches to and a hole in the adjacent frame that seemed too coincidental. I searched through my shop's spring collection and found an appropriate one in both length and gauge. (luckily I had a few that could work) Drove the car and the problem is gone. Then I was reading the forum about this yesterday and copy/pasted someone's pic of the diagram above. Pretty funny how I came upon this diagram after figuring it out. I added some red text and circles for clarification Why has no one above referred to this "pull" spring, in the diagram, above? Everyone seems to be referring to the large diameter, heavy gauge, over the center, push? spring located behind the tach. I'm thinking, both are needed? Why not?

EBSTANG,

I answered on my thread you quuestioned the same:

www.7173mustangs.com/thread-installed-new-clutch-with-diaphragm-style-pressure-plate-pedal-does-not-come-back?action=lastpost

Tim

Tim

Never drive faster than your guardian angel can fly Angel
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#4
great! I just wanted to be sure and get some confirmation from some guys. I also put a very strong spring on there and it seems to be fine. I can't see any reason that a strong spring could hurt anything.

...in looking back at Jeff's post above from 3/27/14 where he states, "you need that spring from the linkage to the clutch fork to bring the clutch fork back and fully release the throw out bearing" I believe that statement made me skip past his post, as it is incorrect. The spring he's referring to only keeps compression on the adjustable release rod between the linkage and the clutch fork. This keeps the rod from possibly falling out during quick shifting. It has NOTHING to do with the return of the pedal. But then on 3/28/14 he speaks of using a brake drum spring and seems to be talking about the return spring we are now speaking of. No disrespect to Jeff, as I depend on kind people such as him for help but sometimes you'll find people will make comments without remembering the DETAILS correctly. When you are the guy seeking the advise, you are specifically interested in the DETAILS. Flippant comments, albeit with good intentions, can cause much confusion. I was making an attempt to clarify (diagrams with the red markings) for myself for confirmation but mostly to leave this thread with the correct info for the next guy, who is struggling to understand. I humbly, thank you all for your help in this forum. I certainly remember the days with no internet!

Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic! thumb

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#5
EBSTANG;215443 Wrote:great! I just wanted to be sure and get some confirmation from some guys. I also put a very strong spring on there and it seems to be fine. I can't see any reason that a strong spring could hurt anything.

...in looking back at Jeff's post above from 3/27/14 where he states, "you need that spring from the linkage to the clutch fork to bring the clutch fork back and fully release the throw out bearing" I believe that statement made me skip past his post, as it is incorrect. The spring he's referring to only keeps compression on the adjustable release rod between the linkage and the clutch fork. This keeps the rod from possibly falling out during quick shifting. It has NOTHING to do with the return of the pedal. But then on 3/28/14 he speaks of using a brake drum spring and seems to be talking about the return spring we are now speaking of. No disrespect to Jeff, as I depend on kind people such as him for help but sometimes you'll find people will make comments without remembering the DETAILS correctly. When you are the guy seeking the advise, you are specifically interested in the DETAILS. Flippant comments, albeit with good intentions, can cause much confusion. I was making an attempt to clarify (diagrams with the red markings) for myself for confirmation but mostly to leave this thread with the correct info for the next guy, who is struggling to understand. I humbly, thank you all for your help in this forum. I certainly remember the days with no internet!
Just for further clarification, as it seems some may not have fully grasped this "clutch return" up to this point, I have written a dissertation on the subject. Please...tell me if I'm wrong but I don't think so. Again, I reiterate, the intent is to get the correct info out on the forum to HELP others who are in need of information. If you'd like to debate, I welcome it, as that is how I/we learn from each other. If "you cannot handle the truth" and learn something new and your feelings get hurt 'cause something you posted was wrong, sorry. I tried to be gentle but you must r e a d and let the information in before to just try to defend your incorrect position. That being said, what's done is done and I will certainly let bygones be bygones. (Hope he understands...but he's probably pissed) Here's how I see the "Clutch Return Issue" (atleast in my '73)
There are two "pull springs" located under the floor, outside of the car and one "push spring" located in the car, behind the tach in the dash. Each of the two exterior pull springs attach to one of two arms extending from the equalizer bar (z-bar) The equalizer bar rotates as the clutch pedal is pressed. The clutch pedal/arm is connected to a "clutch equalizer rod," (see diagram) under the dash and passes through the floor and connects to the first arm of the z-bar (frame side). It has a cotter pin to keep it intact. Just above that connection point, on the arm, is a second mounting hole. This hole is for the first "pull spring". (This is the spring I was missing) This "pull spring" spring also attaches to an adjacent hole on the frame. Since only one end of this spring can move (it's attached to the arm on the z-bar) and the other end is attached to a fixed point (the frame of the car) the pulling force will pull the arm of the z-bar toward the frame of the car. This direction is downward. The equalizer ROD, which is attached (and cotter pinned) to this arm, right next to the spring, will also get pulled downward by this spring. As the equalizer ROD is pulled down (through the floor), it pulls/rotates the clutch pedal/arm up, since it's attachment point on the clutch pedal arm is above the mounting pivot (axis of rotation). Therefore, having a pull spring attached to the "frame side z-bar arm" connecting it to the frame, WILL return/help to return the clutch pedal to the "UP" position.
When the clutch pedal/arm is pressed down, (the pull spring attached to the z-bar arm and the frame, under the car, is stretched out) the attachment point, of the clutch pedal arm & the equalizer rod (up under the dash) reach a zenith point "middle" (directly above the pivot point where the clutch pedal arm is attached to it's mounting bracket) and then continues to rotate "over-middle," as the pedal reaches the floor. It is at this point that the third spring (a push spring) the large diameter, push spring, behind the Tach, in the dash bumps/pushes the clutch pedal arm back "over center." (If it's working correctly- bushings can be worn lessening it's effectiveness)
The last pull spring is attached to the other z-bar arm, under the car. It's other end attaches to the clutch fork (clutch arm sticking out of the transmission's bell housing) This pull spring's sole purpose is to keep compression upon the adjustable release rod so that it cannot lose contact with the clutch fork and fall out during quick shifting. Mechanically speaking, this pull spring is attached to two parts which move (the z-bar arm and the clutch fork) Since both parts move, the pull spring does not move either part. It merely holds them together. As the z-bar is rotated by the "frame side" z-bar arm being pulled up (clutch pedal being pushed in) the "trans side" z-bar arm is rotated rearward, pushing the adj release rod into the clutch fork, disengaging the clutch. You adjust the adj release rod's length to a point where, while the clutch pedal is in it's up position (disengaged), you can feel some (very little but some) play between the adj release rod and the clutch fork) If it's adjusted too long (preloaded) you will have unnecessary clutch wear.(from being partially disengaged)
The spring which attaches to the clutch fork does not pull the clutch fork forward. With no spring attached to the clutch fork, the clutch fork will return to the frontward position. (engaged)
Really hope this helps someone...wow!

Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic! thumb

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#6
Nice and detailed essay about the function of the clutch system!

Thank you!

Even better with your real name, unnamed stranger Wink Tongue

Tim

Tim

Never drive faster than your guardian angel can fly Angel
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#7
I agree with Tim, thanks for the well thought-out write up. I just wanted to throw out there that your last comment about the spring from the equalizer bar to the throw out fork (that holds these two under tension so that the adjustable rod doesn't fall out) not retracting the fork might not be 100% accurate as the frame side spring being under tension will want to pull the pedal off of the floor up to its stop. This should pull the fork side arm of the equalizer bar forward (towards the front of the car) which will pivot the clutch fork and pull the release bearing away from the clutch pressure plate.

I wanted to make this point as the release bearing used with the older style clutches is not designed to stay in contact with the pressure plate- it will burn up. There is supposed to be an 'air gap' between the bearing's race and the pressure plate fingers.

However, the release bearing used with modern, diaphragm-style pressure plates IS designed to stay in contact. Not sure on the reason, probably pedal feel and system smoothness, but I think this is an area where people get tripped up when modifying the stock system to use either modern clutches or different actuation/ release of the clutch (i.e. hydraulic or cable vs. the stock mechanical linkage). Conversion to a modern, non-OEM style clutch or alternate actuation system requires checking the pedal travel and clutch release and engagement points to make sure that the pressure plate isn't over-centering or partially dis-engaged...

I wanted to throw my $0.02 in the ring as there have been a few posts about pedals sticking and underdash assist springs, and I went through this when converting my old Sportsroof from the mechanical linkage to late model 5.0 HO/ T5 combo using Modern Drivelines cable setup.

Let me know if you don't agree, I've been way wrong before!

-Matt
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#8
It does move the clutch fork when the z bar reaches the limit of it's movement and my original point wasn't in reference to a T-5 or a diaphragm style clutch. In hindsight my wording should have said "fully release the throwout bearing from the clutch fingers". Keep in mind the clutch pressure plate and springs pull the throwout bearing forward when the clutch pedal is released.

I'm not sure what the big deal is. The pull spring between the clutch fork and the z bar is necessary and in my experience having it in place helps cars that have pedals that stick to the floor on occasion. Your pedal stuck to the floor without it and worked properly with it.

If you want to demonstrate how smart you are by complaining about my lack of understanding, go ahead.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#9
Jeff, omg, seriously, for the third time, I wasn't missing the spring from the clutch fork to the z-bar arm. I was missing the one from the other z-bar arm to the frame. (that's why when I put a spring on there, it raised the pedal)

Matt, I hear ya, but the spring to the frame causes the rotation of the z-bar and consequently both arms welded to it. If there was no spring between the second arm and the clutch fork you could get separation and the release rod could fall out. The internal "clutch pressure plate and springs pull the throwout bearing forward when the clutch pedal is released," as my colleague Jeff explains above...when this occurs the clutch fork returns forward. Try pushing the clutch fork rearward with no spring attached...it returns on its own. The external spring is there because you may on occasion depress and release the clutch pedal FASTER than it would return on it's own. This spring holds them together. The frame spring does the pulling. The frame spring has a fixed end (to pull) and is much stronger because it pulls.

Let's put it this way, just for fun. If Mary is holding onto Nick's hair and I pull Mary away from Nick, did Mary pull Nicks hair or did I?

I knew nothing about this 4 days ago, I will take this knowledge to my grave, that I am sure. For that I am thankful to the Forum, as I am a little "smarter" for thinking through it.

On a side note, Jeff, thank you for answering another question I posted on the Forum this morning, and for sticking with it as you are not the first to think I'm stubborn and tenacious. You must be to get to the bottom of things.
tease
Eric "The Red" lol

timachone;215598 Wrote:Nice and detailed essay about the function of the clutch system!

Thank you!

Even better with your real name, unnamed stranger Wink Tongue

Tim

Eric's my name, thinking's my game. Wink

Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic! thumb

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#10
Well Eric, I never posted advice to your problem. What I saw was you talking about my prior post. I agree if you were missing that spring it would cause a problem.

Nevertheless . . . Big Grin

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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