TR2/3/3A Clutch hydraulics ?

[Lukens]

Getting aggravated.

Should not the return spring on the slave pull the plunger all the way to it's fully retracted position?
When I adjust the slave pushrod with a little clearance and work the clutch, the clearance is disappears. Run the rod in the clevis to achieve more clearance, work the clutch, and that clearance is gone. I can keep doing this until all the adjustment on the rod is gone, and the plunger just creeps further and further away from fully retracted. However, I can force the plunger home with my hand.
I'm considering a longer, stiffer, spring. (Aren't we all? lol)
Russ

 

[Geo Hahn]

Have you tried omitting the spring altogether? As I mentioned in the other thread -- that is the only way mine will work.

I probably have a broken pin that engages itself to disengage the clutch but allows the fork & operating arm to return to far if the spring is in place.

I omit the spring as a stop-gap fix until the day when I need to take the gearbox out -- but that day is a long time coming (so far).

 

[TR3driver]

Yes, the idea is that the return spring should be strong enough to always bottom the piston in the slave cylinder.

However, for that to happen, the master cylinder has to open the 'foot' valve to allow fluid to flow back into the reservoir. You might check to be sure that is happening. Eg the pedal returns all the way under just the influence of it's return spring, and there is some free play in the MC pushrod when it does. I have also had the spring inside the MC break (4 pieces by the time I figured out the problem), which was causing the piston to not return fully.

Also, the slave spring is a special, very strong spring. Lots of people try to substitute some other spring (like a screen door spring) with disappointing results. I've also managed to ruin a few slave return springs by over-stretching (probably when I had a broken taper pin).

 

[Lukens]

I must be dense... humor me here.
Let's take the clutch operating arm out of the picture all together... disconnect it and the external spring. The clutch pedal is up. The MC has it's own internal spring that has pushed it's plunger (piston) all the way to the end of it's stoke. When in this position, the slave piston would be fully "retracted"... deep in it's bore. Now if I push the clutch pedal, juice will force the slave piston out. If I relax the pedal, the spring in the master will push it's piston back to it's free position. This will draw the slave piston back into it's retracted position. Unless I'm really, really missing something, this is pretty simple?
Now let's connect the operating arm. The external slave spring is going to keep the slave's rod tight against it's piston. Am I right so far? If this is the case, how will I establish the recommended clearance (.010) between the two.
Like I said, humor me.

 

[Geo Hahn]

....The external slave spring is going to keep the slave's rod tight against it's piston. Am I right so far? If this is the case, how will I establish the recommended clearance (.010) between the two...

I think the clearance is at the other end of the rod -- that is, it is the freeplay before the rod begins to move the operating arm. It is my understanding that this assures that the TOB isn't riding on the fingers the whole time.

 

[TR3driver]

With the slave return spring connected, you aren't going to "see" the free play at all. The spring pulls the arm and pushrod back against the piston hard enough to push the piston all the way into the slave cylinder. Ignoring any slop in the clevis, all of the freeplay normally winds up being between the TOB & pressure plate levers.

So, to set the free play (which is supposed to be much larger than .010" at the slave, more like .100" depending on which source you believe), you have to move the arm until the TOB presses tightly against the PP levers. The most straightforward way to do this is to temporarily remove the spring and then reinstall it later.

But, it's easier to just grab the lever and see how far you can pull it away from the slave against the tension of the spring. It does take a certain amount of strength to fight the spring, so if you are not strong enough, you may need to find some way to increase the leverage (or just do it with the spring disconnected). I usually just "eyeball" the adjustment, as long as it is somewhere between 1/16" and 1/8", the clutch seems to work fine for me. My feeling is that the given specification is somewhat larger than actually required, in order to allow for clutch wear before the next adjustment.

If you want a more accurate measurement (or to make the adjustment), then loosen the locknut and unscrew the pushrod from the clevis just enough to eliminate all the free play (meaning you can't pull the lever any farther away against the spring pressure). Now turn the locknut without turning the pushrod until there is a 0.1" (Girling) or 0.08" (Lockheed) gap between the nut & clevis. Next turn the pushrod back into the clevis, letting the locknut turn with the rod, until the nut just touches the clevis. Tighten the nut and you're done. This process is in the workshop manual, pages D4-D5.

PS, not mentioned, but perhaps significant, the slave piston should be pushed into the cylinder as far as it will go before checking the freeplay. Normally it would be there already from the action of the spring, but it can't hurt to push on the pushrod and see if it will move more.

 

[Lukens]

Randall, I understand... best to check free play with the spring disconnected. And I don't know why I said .010? I usually just give it some play by feel, maybe 1/32 or more. I always check it frequently to confirm that it free.
I'm back in business now. The problem was that the slave seal was so too tight. The slave spring couldn't override the friction. The clutch fingers would push the TOB back to their limit but the slave spring couldn't push the piston back further. Then I'd shorten the rod to create freeplay and the same scenario would repeat. Each time I did this the piston would inch it's way out of the cylinder.
I can't figure why the seal was so tight. I replaced it less than 1000 miles ago. I'm using Castrol GTLMA synthetic. Anyway, I replaced the slave and everything is working as it should.
One other thing. I mounted the slave on the tranny side of the bellhousing. I had to cut 1/2" off of the slave push rod to get freeplay. Strange?

 

[TR3driver]

One other thing. I mounted the slave on the tranny side of the bellhousing. I had to cut 1/2" off of the slave push rod to get freeplay. Strange?

Do you mean the slave on the rear side of the bracket? That would do it. Bracket on the rear side of the flange would be normal, unless you have a later TR6 gearbox fitted (like mine).

It's confusing because the manual shows the earlier Lockheed slave, which mounted differently than the Girling slave. This is the correct setup for Girling


I also found that, when I shortened the pushrod, the spring became too weak to return reliably. I solved the problem by adding a little tab to the slave mount, to stretch the spring an extra 3/8" or (roughly the same amount I removed from the pushrod).

 

[Lukens]

Do you mean the slave on the rear side of the bracket? That would do it. Bracket on the rear side of the flange would be normal, unless you have a later TR6 gearbox fitted (like mine).

It's confusing because the manual shows the earlier Lockheed slave, which mounted differently than the Girling slave. This is the correct setup for Girling


I also found that, when I shortened the pushrod, the spring became too weak to return reliably. I solved the problem by adding a little tab to the slave mount, to stretch the spring an extra 3/8" or (roughly the same amount I removed from the pushrod).

Of course... I've got mine back aswards.