Clutch chatter when warm. What is the cause?

[AEROCOOK]

I just finished replacing the clutch in my 98 Legacy and I now have fairly severe clutch chatter but only when warm. If the car is started cold and driven right away, it will not chatter for the first 10 to 15 minutes but once warm, it chatters on take off. I've searched for other posts on clutch chatter and it seems it typically occurs when cold and goes away when warm, which is completely opposite of my issue. 

Looking for ideas on the possible cause, can anyone offer up some wisdom?  

Edited October 8, 2014 by AEROCOOK

[AEROCOOK]

I wanted to add that the clutch kit I bought is AMS Automotive brand, they have a tech support number so I gave them a call. 

The person I spoke with hadn't heard of my issue though he did have a theory as to what may be causing it...  

He asked me about the condition of the quill (shaft housing) that the release bearing rides on, I told him there were some high and low areas and that the release bearing was fairly snug on the shaft, enough that the bearing didnt move freely on the quill, there was some resistance. His theory is that since the bearing was already snug on the quill that perhaps when it got up to operating temperature, the metal quill is expanding enough to make the bearing even tighter thus not releasing as freely as it should.

Any thoughts on this theory?

[Fairtax4me]

There are issues with the quill on these because the quill is aluminum. The problem is not due to expansion/heat, but due to wear from the TOB sliding on the soft aluminum. It wears a ridge in the quill which will cause the TOB to twist a bit as it engages the pressure plate which then causes uneven release pressure on the clutch disc.

There are sleeve kits available with a new larger TOB to correct the issue but they're usually pretty pricey. Alot of the aftermarket clutch kits I see now have a sleeve kit included.

A worn quill usually will cause clutch chatter at all times, hot or cold, but can get worse when the clutch is hot. If your new TOB was a fairly tight fit, the quill on your trans is probably not excessively worn. 

 

Another thing that causes clutch chatter is a warped flywheel. If you didn't get the flywheel machined, this is the most likely issue. Flywheel warpage becomes much more pronounced when the flywheel is hot, because the clutch disc is only engaging part of the flywheel rather than the whole thing. This causes higher heating of the surface where the disc does make contact. 

[AEROCOOK]

I didnt machine the flywheel because there was no blueing or signs of overheat and the original clutch didnt chatter at all so I thought it would be okay, sounds like this was a mistake on my part. 

I've become quite familiar with removal and install of the transmission since I've done it twice in the last month, this will be number three!  

I'll be machining the flywheel and installing a quill repair kit just to play it safe.

Thanks for the input.