The dreaded SC clutch cable adjustment...again

[3.0schotrod]

Hi all,

So my clutch pedal on my 3.0 sc started acting up, not returning all the way up. Turned out the bolt and locking nut that sets the 1.00mm and 1.2mm gap had come loose, easy fix...maybe.

Car had a new clutch, flywheel and fork/TOB about 10,000 km ago. Are that still good, no idea without taking the engine out, so lets pretend for now that they are ok.

I checked the pedal box, clutch arm is nice and free and everything else looks good. So I set my 1.2mm gap with clutch cable slack, then adjusted the gap to 1.00mm with the lock nuts at the tube that attaches to the tranny with the 2 x lock nuts. HOWEVER, I had adjusted the clevis on the pedal end by screwing it on 3 extra turns because I thought the cable had stretched a little, before I started all this, clever little me. probably not. With it all adjusted, and the stop on the wooden pedal board adjusted to its max possible travel, I have 23.5mm travel, we all know it should be 25 +/- 0.5mm measured under the car at the tranny. So how do I get the extra 1 to 1.5 mm travel I need to get 25mm +/- 0.5mm. Well im thinking that screwing the clevis on an extra 3 full turns initially might have messed me up with all the other measurements. I feel like the positioning of the clevis, especially if one were replacing with new cable and you have no reference, is critical to be able to achieve all the other measurements we need. In fact nobody seems to detail how this is done properly in any thread 'ive seen, it seems to be kind of mystical, nobody wants to talk about it. Any ideas. If not, im going to unscrew the clevis 3 x full turns and start again and see what I end up with once ive adjusted everything else.

And on the topic of where the threaded tube with the 2 x lock nuts that clamp on the tranny are supposed to sit, I read 22mm, 20mm and 8mm, I wish I could see a picture showing what that means, anyone got a picture, thanks.

[2jmotorsports]

The amount the threaded end is screwed into the clevis is not arbitrary. It has a very specific range and if its not within it, you wont be able to dial in the rest of the procedure at the gearbox. I went through this exact same thing when I reinstalled a fresh pedal assembly, cable, and clutch assembly in my SC.

[theiceman]

i would think if your pedal board is at adjustment is already set for maximum throw and you are still not getting the throw you need, the problem is the set position you are starting with is not right.
I think the clevis just puts you in range for the adjusting nuts and if you are in range for that you are fine ..
The first thing i would check is that your helper arm is moving freely and not binding on the shaft. That has to be completely free so the set position can be done properly then set your gaps. by a adjusting to your 1.0 and 1.2 you are pulling the pedal up away from the board and this is what is going to give you your set position before you start your motion for your travel. I think the issue lies under the engine. Not in the footwell.

[3.0schotrod]

thanks 2jmotorsports and theiceman.

I spent some time today just thinking about the clevis adjustment versus the sheath position adjustment on the transmission.

It suddenly dawned on me they are two different things.

The clevis adjustment actually increases or decreases the actual length of the cable, obvious.
But, the sheath position adjustment that locks to the transmission, actually makes the cable have to travel a shorter or longer distance (that doesn't sound exactly right, but at say one extreme of adjustment there may be 2 ft of cable in the sheath between the firewall and casting on the gearbox, and 2ft 1" at the other extreme of adjustment, the distance is different, I made up those figures obviously), regardless of its actual length of the cable itself. I hadn't thought about that one enough.

I will slacken the cable off again, return the clevis to its original position again, check the helper arm is moving freely, re set the 1.2mm and then adjust on the cable sheath at the tranny end to get my 1.00mm, then check I have 25mm of travel +/- 0.5mm. This is going from frustrating to interesting now, to see the effect of different adjustments, or combinations of adjustment.

[3.0schotrod]

So I did all that I said above in my previous reply apart from I ended up backing off the clevis 2 full turns rather than 3 and 1/2 I had adjusted originally. Well my end result is exactly the same pretty much, I get 23mm of travel.
Lets think about exactly what happens when I bury the pedal and I only get 23mm.
If I take the floor board out, and repeat the test, I still get 23mm, the pedal is not on the floor and if you pressed really hard you would probably shear the roll pin in the pedal assembly. So what exactly are we maxing out. Well im guessing the fork thats on the throw out bearing is at its max travel, that's only a guess though.

So lets pretend we drop off the helper arm, the long and short arms, and notch the short arm round one spline (towards the back of the car) set it all up again, where would we be, well im guessing right back where we started with 23 mm of travel, in fact we may find that we cannot attach the cable sheath to the tranny because everything is out of position. So where does that leave us. To get 2mm more travel, with the floor board out of the car, so we cant blame that from stopping us, what are we maxing out on.

[yelcab1]

If you are shifting well at 23mm max travel, I would leave good enough alone. Check it again in 5k miles. You might find that after things have a chance to wear in, there may be more clearance to achieve 25mm. I have never found it an absolute requirement to meet those specs, especially the clutch travel and the free play.

In the end, how does it feel, how does it shift, how does it drive? That is what matters.

[Walt Fricke]

You don't want to overstroke - hard on the pressure plate diaphragm spring. You don't want to understroke so you just touch the pedal and you can shift - because even if this doesn't put extra wear on the TOB, it gives you no room for a little clutch disc wear. So somewhere in between, to taste - do you like a fairly high pedal, or a low one?

Plus you want the amount of travel which allows the harp spring to do its magic.

I assume you have checked to see that the Bouden tube is seated on the steel tube which goes into the tub?

On the other hand, for a long while I had a pedal position I didn't like and I futzed with all these adjustments - clevis, tube, short arm bolt until things were really screwed up. Advice from a mechanic to try going by the book got it back to reasonable function.

[3.0schotrod]

Hi yelcab1 and Walt Fricke.

I think I will leave as is, the pedal is in line with the brake pedal, no problem for me there, it bites half way up, no issue for me there, it feels fine, it shifts fine. The steel bowden tube is seated in the tub, no issues there. I'm wondering if the clutch wears, say 1mm or 2mm and so on over time whether you end up getting more stroke anyway as you said, that makes sense to me. In other words 2mm gets worn off the clutch over time and my stroke goes from 23 to 25 mm, would make sense to me. At the end of the day if you disconnect the cable at the gearbox end and manually lever the clutch (if you could, hypothetically) there is only a certain stroke from clutch fully engaged with the flywheel to fully released where something bottoms out. And if that distance equates to 23mm overall (assuming fork isn't cracked) then that's all you get. Its almost as if my new clutch is 2mm too thick, i'm sure it isn't, but you get the idea.

Last thing I will check, under the rubber boot at the tranny end, making sure the cast on hook/loop on the end of the clutch cable isn't running into the end of the metal tube where it adjusts, you cant see for the rubber bellow, i'm sure it isn't, but tha'ts the only other thing that could reduce stroke/travel in relation to the cable and its different adjusting locations.