Clutch noise

[Mustlust]

Hi all,
just working through last of the jobs on the restoration project and noticed a screeching noise from the clutch. I have a minor leak in the old slave cylinder and will replace this in the next couple of weeks and clutch operates well enough.
if I put the smallest amount of pressure on the pedal the screeching stops, although I think the noise returns when gear engaged and driving along.
Is this a simple case of adjusting the tension on the slave push rod?

[mick88]

Are you sure it is the clutch making the noise and not a bearing or something in the gearbox?
If it were the spigot bush or the thrust bearing it would occur when you have the clutch pedal depressed.

Cheers, Mick.

[JDNSW]

Sounds like the collar pushed forward by the thrust bearing is lightly touching the release fingers on the pressure plate - which it shouldn't. Guessing that the reason is incorrect adjustment of the slave cylinder pushrod, or possibly it is sticking - the slight leak may indicate problems with the slave cylinder with both symptoms relating to the same issue.

[Mustlust]

Hi John,
just replaced the slave cylinder and problem hasn't gone away. I'm wondering about the amount of lubrication in the withdrawal unit..... I can't remove the oil level filler plug as its been worn round and won't budge. I filled the gearbox based on volume, but wonder if enough is getting to the front to lubricate the unit.
Is it possible to have too much oil in the gearbox? If I put in another litre with the intent to free up a possible stuck withdrawal sleeve, what could go wrong? Or maybe 2 litres?
The clutch works well and the sound is only noticeable (like a rubbing screech) at idle and out of gear with foot off clutch pedal. I like you're idea of the sleeve rubbing on the release fingers, I can visualise this and it makes sense.
Like I said earlier, a little pressure stops the noise.
Thanks,
phillip

[JDNSW]

Yes. If you put too much oil in the gearbox you will have oil on the clutch. There is no front seal to the gearbox, only a spiral groove that pumps the oil on the shaft back into the gearbox, but obviously this only works when the engine is running. Overfill the gearbox and park nose down on a steep hill, and the oil will end up on the clutch - which you don't want.

A thought - check that you do not have lost motion where the slave cylinder bell crank is coupled to the clutch release shaft. This is by a short pipe with a pin through each shaft. If these pins have been replaced with a bolt or the wrong pin, they may be partly sheared, resulting in lost motion, which possibly could have this effect. Both the pins and the pipe are very hard, and need to be as they have a high load.

[Mustlust]

Have checked slave cylinder rod adjustment as per handbook and also checked the fork shaft and all looks ok.
Im thinking that I will just have to slide the gearbox back and take a look at the release bearing and the clutch components. The bearing is a simple $20 swap and I can check the collar offset as the book stipulates a specific dimension. Can also run a little lube over the collar to ensure it slides easily. Will also check pressure plate springs. Anything else to check???
I have run the box through all gears with the transfer engaged and disengaged and the noise only occurs when clutch pedal is up, I.e. Not depressed. So I'm thinking it must be in the clutch.

[Mustlust]

Have checked slave cylinder rod adjustment as per handbook and also checked the fork shaft and all looks ok.
Im thinking that I will just have to slide the gearbox back and take a look at the release bearing and the clutch components. The bearing is a simple $20 swap and I can check the collar offset as the book stipulates a specific dimension. Can also run a little lube over the collar to ensure it slides easily. Will also check pressure plate springs. Anything else to check???
I have run the box through all gears with the transfer engaged and disengaged and the noise only occurs when clutch pedal is up, I.e. Not depressed. So I'm thinking it must be in the clutch.

I have identified the problem. As JD suggested, the withdrawal sleeve is rubbing along the clutch and causing a screech. It isn't retracting enough when the foot is off the pedal.
When I disconnect the connecting tube that links the mechanism to the slave cylinder it withdraws ok. So, the resting tension placed on the withdrawal unit is too much.
Now on the new slave cylinder, the piston doesn't withdraw as the master would. Does the slave have a return spring? If not, what forces the piston back up the cylinder?

[Mustlust]

Maybe last question
how free should the withdrawal sleeve spin?
the noise happens as the sleeve drags across the clutch fingers when not fully pressed into the clutch.
I put my fingers into the inspection hole of the bell housing and cannot turn the sleeve at all. If the bearing was new, I guess there would be fairly reasonable free turn on the sleeve.
Maybe the bearing just doesn't spin as it should. If it did, it really shouldn't matter if the sleeve is slightly touching the fingers as it would spin and not drag.
is this correct?

[JDNSW]

That is correct. It is unlikely that the bearing is dragging, as it is inside the gearbox, but it is barely possible it is sticking where the withdrawal sleeve goes into the gearbox.

Thinking about it, I suspect the sleeve is meant to touch all the time, and spin with the flywheel, as there is a spring in the slave cylinder that pushes in the same direction as the fluid. If the slave cylinder is sticking this could have the effect you see.

Another thought - the correct pressure plate for this vehicle, if it is the diaphragm type with lots of little fingers, should have a steel ring between the fingers and the release sleeve. This is not there on the Series 3 pressure plate, and I wonder if having the wrong pressure plate could be the issue?

[Mustlust]

Aha....
no diaphragm on the clutch.
i think we might have it