RTH: Clutch fork, hub, and T/O bearing questions (1 Viewer)

[RWBeringer4x4]

Yep - that's really my final question. The clutch slave piston, aside from being forced forward by hydraulics, also appears to be spring loaded - so to get the answer as to the length I need for the new (or modified) pushrod, I need to know if I should be forcing the piston backward completely (bottom it out in the bore, against spring pressure) and measure what I need from there, or if I should have it resting on the piston in its native (unsprung) state.

Any thoughts on this last part? If the piston needs to be fully compressed to bottoming out, then my stock rod really isn't THAT far off. If the piston ISN'T supposed to be compressed at all, then the final rod needs to be significantly shorter than stock (probably 2 inches).

 

[middlecalf]

I have to defer to more knowledgeable folks, but my gut feeling is neutral for the slave and adjust the rod. Simple reason being if something happens to the external spring and it’s the forcing function for full clutch engagement I think that would lead to a worn throw out bearing quickly.

 

[pb4ugo]

I maybe wrong, but as I recall , there's no spring inside of the slave. I m pretty sure it's just a piston with a seal. When I setup mine, I pushe'd the piston all the way into the bore to determine how long the rod needed to be. I turned the adjusting nut so the rod could be shorten a little, but most of the adjustments would make it longer. Remember you want to make sure the piston doesn't exit the cyldr when the clutch is depressed.

 

[RWBeringer4x4]

I maybe wrong, but as I recall , there's no spring inside of the slave. I m pretty sure it's just a piston with a seal. When I setup mine, I pushe'd the piston all the way into the bore to determine how long the rod needed to be. I turned the adjusting nut so the rod could be shorten a little, but most of the adjustments would make it longer. Remember you want to make sure the piston doesn't exit the cyldr when the clutch is depressed.

Odd - I could have sworn yesterday when I was fiddling around with things that the slave piston felt spring-loaded. At the same time, it doesn’t make much sense to have a spring in there forcing the piston forward unless it is simply to serve as a stop to prevent the hydraulics from sucking the piston back too far when you let off the clutch.

Obviously without the hose attached and the cylinder drained there is no residual hydraulic pressure...

 

[pb4ugo]

If it's your used cldr, I wouldn't force it. I maybe wrong or there' could be debris on the cyldr walls behind the piston.

 

[pb4ugo]

I'm wrong, just checked one of new ones and it has a spring in it.

 

[RWBeringer4x4]

Funny I was just digging up schematic diagrams and was about to say you were right, but found a few more photos of rebuilds on mud that had springs. Looks like there were no springs in pre ‘74 cylinders.

Question remains - does that spring get fully compressed to determine slave rod length? I guess if I’m building my own, I could just thread half the rod and have it be basically infinitely adjustable.

Round stock is cheap - maybe thread one for test fitting them build a second for “looks.”

 

[jim land]

maybe it is better not to force the piston in the cylinder like i have done , it could be why my clutch pedal is adjusted to the max and it is still engage to close to the floor (grinding gears between first and reverse)

probably better to let the rod sit in a neutral position to set your rod length as other said

 

[RWBeringer4x4]

I think this is probably right. The only thing I can figure is that the spring is there to prevent the clutch piston from retracting too far back into the bore. I imagine when all is said and done, a small amount of pressure against the spring would keep the piston “located” appropriately and lightly spring loaded, thus solidly mounted agains the pushrod and “ready to fire” when the clutch pedal is depressed. Too much pressure, obviously, would just push the throw out bearing forward into the pressure plate (as it currently is) so clearly there is a happy medium between not letting the rod and piston flop around in the bore and adding forward spring force onto the fork. I’ll start there and make sure the rod I build has adjustment in both directions.

 

[middlecalf]

Or is the spring a return (tension) not compression?

 

[RWBeringer4x4]

Strong possibility a would just depend on whether it “floats” in the cylinder or of its connected to the piston and booster. I had one of these apart but it was a several years ago - I seem to recall it floating.

 

[RWBeringer4x4]

Alright -

Custom rod, custom bracket, everything is mounted. It’s not under hydraulic pressure yet, but as it sits this setup holds the throw out bearing off the pressure plate by about 1mm.

Even with the adjustment maxed out on the bracket, I’m not super happy with the angles I’m dealing with for the push rod.

The downward angle is pretty extreme and I can’t see the slave lasting long in this configuration.

I’ll likely try to drop the slave using spacers from the bracket but suspect the mounting bolts will interfere. Even the lower profile Allen head bolt will likely conflict with the slaves mounting ear.

If I can’t get this to work I’ll likely countersink the bracket and get a couple of countersunk Allen bolts to go in it.

 

[RWBeringer4x4]

Spacing it down helps with alignment for sure (again, I would need to countersink the bracket to make this possible long term)

The other issue is the ridiculous amount of slop in the pivot point. The fork wants to “sag” off the pivot - the little spring clip on the fork does little to hold it in place.

The return spring makes it worse - it actually pulls the fork forward and down on the pivot. This brings the whole fork closer to the pressure plate and sacrifices precious millimeters of throw.

This could be an issue with the spring angle, since the spring now sits below the fork.

This is starting to make me insane. Does all this get locked in place by hydraulic pressure once it’s hooked up? Is there any point to messing with it before it’s in the truck? There is so much slop in the system it’s tough to make a judgement call.

 

[brian]

there is no pressure in the system till you step on the pedal.
the springs on the pedal and fork pull the slave back so the release bearing isn't riding the pressure plate fingers.

 

[RWBeringer4x4]

@brian,

So is it normal for there to be a ton of play at the pivot ball when there is no hydraulic pressure?

The little spring holding the fork to the pivot definitely doesn’t seem strong enough when not under pressure, the fork wants to sag off the pivot, falling forward and down.

 

[brian]

make a bracket (or it even looks like you had one in a previous picture) to properly mount the slave return spring, with some tension(the spring should never completely be relaxed) inline with the push rod/ slave cylinder. your spring not being in line is not helping you.
yes there is much play in the whole works, hence the importance of the springs doing what they need to do. that slave return spring will pull the fork back and keep it riding on the pivot.
for-instance, not having a clutch pedal return spring would allow the pedal to sag down and allow the slave to push the release bearing into the fingers.

 

[RWBeringer4x4]

Took a video to try and illustrate - if this is normal I’ll bolt everything up and see if I can adjust it once it’s back in the truck.

 

[RWBeringer4x4]

make a bracket (or it even looks like you had one in a previous picture) to properly mount the slave return spring, with some tension(the spring should never completely be relaxed) inline with the push rod/ slave cylinder. your spring not being in line is not helping you.
yes there is much play in the whole works, hence the importance of the springs doing what they need to do. that slave return spring will pull the fork back and keep it riding on the pivot.
for-instance, not having a clutch pedal return spring would allow the pedal to sag down and allow the slave to push the release bearing into the fingers.

The bracket in the previous picture was the same bracket. I spaced the slave down to get better pushrod alignment, which in turn moved the bracket down, which resulted in the spring angle you see in the more recent pictures.

 

[65swb45]

If the prongs on the fork do not hold the fork securely to the pivot, it’s time for a new fork.

 

[RWBeringer4x4]

If the prongs on the fork do not hold the fork securely to the pivot, it’s time for a new fork.

Hey Mark -

This fork was actually from you, (by way of Downey) about 2 years ago. It hasn't been run (although I think it was used). There Didn't appear to be anything wrong with it when it went in. I cant imagine those little prongs taking the full weight of the fork and holding anything in place, even if they were brand new. The prongs also didn't seem any better/worse than the ones on the fork this fork replaced. Then again, the truck had clutch issues before I tore it down so maybe both forks are toast?