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Old 07-23-2011, 09:14 AM
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Unusual Clutch Issue

After chasing down a clutch chatter problem for way too long, I finally seemed to fix it, but I really don't understand how.

I adjusted the rod between the slave cylinder and clutch fork for very little play vs the specified 1/4" of play. Chatter is now gone, although the odd time a tiny bit might show up.

I'm not sure why this helped. Wild arse guesses include loose clutch fork pivot, contaminated clutch fluid, faulty slave or master cylinder.

I did bleed the slave cylinder in an earlier attempt to fix this issue, so there wasn't any air in there.

Slave is also bolted to bellhousing, so that wasn't the problem either.

I can hear a little clicking when I operate the clutch now, which wasn't there before. Doesn't matter if engine is runnning or not, although when it's not runnning I think it's a single click.

Just did this yesterday, so I need to do some more test driving and listening to get more clues as to what's going on.

In the meantime, anyone have any idea of how removing most of the throw-out bearing play stopped my clutch from chattering when engaging the clutch in 1st gear?

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Old 07-23-2011, 12:34 PM
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2 things that may cause your problem is weak clutch plate diaphram or worn flywheel that needs re-surfaced.
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Old 07-23-2011, 04:48 PM
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I am thinking the throwout bearing has lost the cage to retain the balls.(chewed up) and now the bearing is clicking and not staying concentric as it turns, probably due to the balls all grouping up and crowding to one side.Just a thought. IIRC you have new pressure plate and disc .Yes?
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Old 07-23-2011, 06:44 PM
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I've already had the clutch apart and everything still looks new (only 5500 miles on it), except for the clutch disc which has darkened up a bit. McLeod says that's normal. The throw-out bearing rotated fine.

I've checked all u-joints, rear suspension, differential, engine mounts, replaced tranny mount.

I recall, that when I bled the slave last year, I did get some improvement for a while. Now when I lengthen the rod between the slave and clutch fork, the chatter goes away. Only difference i can see is less fluid in the slave cylinder.

I am using DOT 5, and the fluid is quite old now. 15 years and only 5500 miles.

From what I understand, DOT 5 won't absorb moisture, but can get aerated easily.

It does seem like the slave is acting like a spring when it was extended further with the short rod and more fluid in the cylinder.

The clicking seems to be coming from the clutch fork pivot point (an "L" bracket riveted to the bellhousing) but I need to confirm this.

I find it very curious that lengthening the rod to remove most (but not all) of the freeplay caused the chatter to dissapear.
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Old 08-19-2011, 04:25 PM
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I finally got my new slave cylinder installed and a test run went fine. No chatter.

The slave was leaking, which means air could have gotten into the system (when the slave piston returns, the hydraulic suction could draw air past it).

My best guess is that there is a slight imbalance in the pressure plate. The throw-out bearing wobbles slightly, and the air in the hydraulics amplifies it and causes the chatter.

This may in part be to me using a 3 fingered pressure plate as shown:

The other issue may be using DOT 5 silicone brake fluid. The slave cylinder was leaking, and upon dismantling it, there was some black, almost gooey liquid around the seal and some in the cylinder. Could be from water corroding the aluminum piston, or iron cylinder. Apparently, corrosion of iron without much air can cause black corrosion vs rusty red. But I'm not sure about that.

Anyway, regular brake fluid, such as DOT 3 or 4, would absorb the water and no doubt slow the process down.

Here's a pic, but it's very bad. I tried hard, but it was difficult to illuminate the inside of the cylinder. You can see black staining a little bit though:

I can't explain it 100 percent correctly, but it's interesting as I've neveer heard of a leaking slave cylinder causing clutch chatter before.
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