aparrent hot spot on flywheel

robert walsh · 08-18-2008, 06:45 PM

I have a clutch chatter problem primarily in 1st and reverse. 1983 911SC, i have relaced the mounts, adjusted the cabel etc. problem has gotten better but still there. Clutch has only 20k on it, it has been mentioned here on the forum to take the car on the highway and spin the clutch at higher revs, at 60-70 mph and this may burn off the hot spot or spots, i doubt this would help the situation but has anyone aver heard of this and may it work. Last effort before sprnding $1500 having the clutch relaced. Thanks

javadog · 08-18-2008, 07:37 PM

No.

The hot spots can extend into the flywheel deeper than the surface. Machining is sometimes not enough to get rid of it. Improper machining is also a culprit in clutch chatter.

You may get lucky and not have to change the flywheel along with the clutch. You may not. It's a bit of a crap shoot.

JR

Flieger · Flieger's Garage

Hot spots, at least in brake rotors, can cause the steel to change crystal structures to a much harder and brittle type of temper. If you try to turn brake rotors on a lathe or wear down a flywheel, you will eat up your clutch disc.

robert walsh · 08-19-2008, 04:35 AM

Aside from the hot spot issue can spinng the clutch at high rpm's in any way help to reduce clutch chatter, buurs on the disc or dirt etc., I doubt it, but it was mentioned here earlier.

Peter Zimmermann · 08-19-2008, 06:40 AM

Quote:

Originally Posted by robert walsh

Aside from the hot spot issue can spinng the clutch at high rpm's in any way help to reduce clutch chatter, buurs on the disc or dirt etc., I doubt it, but it was mentioned here earlier.

No. If the flywheel has hot spots they are there to stay - and they can't be machined as was already posted. That said, you might have one of two other problems; (1) your TOB release fork might have a cracked finger, or (2) your mainshaft seal is leaking trans oil and the clutch disc has become contaminated. Engine removal required to repair both problems...

robert walsh · 08-19-2008, 08:43 AM

AS said earlier clutch chatter in 1st and reverse is the problem, any last sugeestions prior to dropping engine?

javadog · 08-19-2008, 09:21 AM

Robert,

Here's a list of things off of the top of my head that can be related to clutch chatter:

clutch cable adjustment (basic adjustment)
clutch cable
pedal cluster
clutch cable hitting throttle rod in tunnel
clutch cable housing length (bow of bowden tube)
motor and transmission mounts
throttle cable free play
clutch release parts
clutch disc
leaking main seal
pressure plate
flywheel

There may be others, these come to mind first, and I'm in a hurry to get out the door to go someplace. These have all been discussed many time here, so try a search for information on the ones that you are not familiar with.

JR

Mattcamp · 08-19-2008, 10:05 AM

If you give it more gas (higher RPM's) when you are taking off in first does that make it chatter less or even not at all???

robert walsh · 08-19-2008, 11:38 AM

If i increase the rpms and let the clutch out slower i pretty much get no chatter, less rpm's and quicker release and it chatter badlly and often stalls.

Peter Zimmermann · 08-20-2008, 07:03 AM

Quote:

Originally Posted by robert walsh

AS said earlier clutch chatter in 1st and reverse is the problem, any last sugeestions prior to dropping engine?

My post, #5 above, mentioned the two most common problems that caused clutch chatter in the 100 + 911s (very conservative estimate) that my shop fixed that had clutch chatter. The two causes covered about 98% of the cars we repaired...please remember, those cars were mostly in technically correct condition owned by regular customers. I can't possibly know if someone has done incorrect setup of linkage or other items on your car, I can only relate what I know from personal experience.

WERK I · WERK I's Garage

Quote:

Originally Posted by javadog

Robert,

Here's a list of things off of the top of my head that can be related to clutch chatter:

clutch cable adjustment (basic adjustment)
clutch cable
pedal cluster
clutch cable hitting throttle rod in tunnel
clutch cable housing length (bow of bowden tube)
motor and transmission mounts
throttle cable free play
clutch release parts
clutch disc
leaking main seal
pressure plate
flywheel

There may be others, these come to mind first, and I'm in a hurry to get out the door to go someplace. These have all been discussed many time here, so try a search for information on the ones that you are not familiar with.

JR

another culprit.....pilot bearing. My clutch would chatter when in repeated stop and go traffic until that was replaced.

hcoles · 08-20-2008, 07:42 AM

I had 0.005 taken off my flywheel to "clean it up" and it was smooth for awhile and now chatters in reverse... if I use higher rpm's it doesn't chatter... and doesn't seem to chatter in 1st. Doesnt' make sense... the clutch is slipping the same direction with forward and reverse... so it could be mounts related. I have new rear mounts and 20 year old trans. mounts like many of us.

robert walsh · 08-20-2008, 11:05 AM

Half hour of time and $60 will answer your questions, but frankly that's all it did for me was answer the question, and for it was "no" that's not the problem, still chattering after all these months.