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Old 05-19-2006, 02:59 PM
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Joe Rose
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Default Gear Rattle

Yesterday I got my '89 911 back from the shop after having a clutch replacement complete with release mechanism update. It seems to me, though, that I'm now hearing more "gear rattle" in higher gears (4th and 5th) when the engine is under load. The clutch disk is of the spring center variety (not rubber), but the one replaced was also of this same design. That's why I don't understand the higher noise level. As a matter of fact, I can feel the vibrations even in my seat when they occur--something I've never noticed before. I've also noted a bit of clutch chatter when slipping it in both forward and reverse. Is this normal after a clutch job or should I be taking it back? The shop I used for the repair is a reputable one.
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Old 05-19-2006, 03:02 PM
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theiceman
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If it is a reputable shop hey will review it with you and fix what is required. No one knows the feel of your car better than you , if you feel it is not right, then it probably isn't. Besides I am sure the guy would like the opportunity to fix what is not right.
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Old 05-21-2006, 09:44 PM
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Hi Joe
I too have had my G50 clutch changed complete with the update kit; the 'symptons' you describe are the same as mine.

I wasn't worried about the rattling but my clutch did also judder slightly in first and reverse; however after some 1200miles, this is disappering. It seems it takes some time for the new bits to bed in....

If you are worried, take it back to the shop to at least register the issues with them. So if in the future the 'problems' still exist, at least the shop can't say you were remiss in not reporting it when you first noticed the noises...
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Old 05-21-2006, 10:51 PM
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Joe Rose
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Thanks for the reply to my post. I am glad to know the slight judder in first and reverse might disappear with some mileage. The noise, however, is annoying when the engine is under load in fourth or fifth gear. I've owned Porsche cars for more than forty years--many being of them being 911's. I've never had anything like this happen before, though. Gear rattle may not be a correct term to use for what I'm hearing. What I'm getting is noise and vibration being transmitted from the drivetrain into the driver compartment. Something, I think, is twisting and touching the body. Perhaps I have a bad motor mount--though you think that would have been noticed last week when the work was done and the engine was out. In any event, I've called the shop and will return the car tomorrow afternoon for assessment. I guess I should post the outcome for those who might be interested. Thanks again for your interest.
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Old 05-23-2006, 05:27 PM
  #5  
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Default Update on my "gear rattle" problem

Yesterday I took my car back to the independent shop that did the clutch job so they could evaluate the increased drivetrain noise and vibration that I noted at certain speeds. They argree it is indeed gear rattle--that noise created by firing pulses that cause unengaged gears in the tranny to vibrate. What I did not know, however, is that the clutch disk they replaced was the original, rubber hub disk and now my car has the spring hub disk. The rubber hub disk was used by Porsche to help dampen gear rattle until owners began experiencing deteriorating rubber problems. The rubber hub was Porsche's solution to the gear rattle problem before going to the dual mass flywheel on the 964. I thought the previous owner of my car had already had the changeover to the spring-center clutch, but I was wrong. Yes, I'm hearing more noise and feeling a bit more vibration under low-speed load in 5th gear, but I guess it's just going to have to be that way. In short, it's normal with the spring-centered disk that's now in my car. I thought some of you might like to know this--especially if you're facing a clutch replacement in your G-50 or earlier car. You just may want to specify the rubber hub clutch if it's still available.
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Old 05-23-2006, 06:02 PM
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Joe: I feel badly for you that you were not given a choice between o.e. rubber hub and spring hub. The rubber hub discs are extremely reliable and will almost always outlast the other components of the clutch. If it were me the shop would be taking the car apart and putting the rubber centered disc in. In addition I'm afraid that your 1st/reverse clutch chatter might be due to incorrect cleaning of parts prior to assembly. Clutch discs must never be touched by fingertips, especially greasy ones! The friction surface of the new pressure plate must be cleaned with laquer thinner, MEK, or similar product. If the packing grease is washed away with an oil-based product a film will remain. Like those fingerprints, that film can also cause clutch chatter. The same goes for flywheels, if it's new it will have a protective coating on the disc surface to prevent rust prior to the part being used. There are even more issues that might cause chatter, but they're rare. Your clutch, spring or rubber hub, should be dead smooth in both 1st and reverse. I was going to post to your thread anyway, because my original thought was that your car actually did have a rubber hub disc, and now we know. I wish you well in making the car "right" to your expectations.
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Old 05-23-2006, 10:15 PM
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Thanks for your concern, Peter, and for taking the time to reply in such detail.
Although I know you're right, I don't think I'll ask the shop to replace the disk with the rubber hub one now. The noise is not really to my liking, but I can live with it. I just don't really feel like going through another round of major disassembly, and I've pretty much dropped the issue with the shop now that I know what it's all about. What I have noticed, however, is the small amount of chatter that was evident on Friday has abated considerably. In fact, I didn't notice it at all today. Hopefully if someone did touch the disk with oily fingers, the residue has already burned off without leaving a glaze. If this issue is not completely gone in a short time, however, I will be back at the shop's doorstep. At the moment, though, I think it's going to be OK. The repair shop I'm using comes well recommended by fellow PCA members in the area. The owner himself is an active PCA member and seems to be a decent individual. He's a Porsche-trained master technician with about 21 years of experience having formerly worked for Hendrick Porsche here in Charlotte. Although it would have been nice to have been asked which disk I wanted, I think the outcome would have been the same. Having read Bruce Anderson's stuff on "exploding clutches", etc. over the years and without having ever experienced "gear rattle" to any extent in any of my previous Porsches, I would have opted for the spring hub anyway. Nonetheless, I appreciate knowing that the rubber hub disk is still available and I hope other owners reading this thread will now be more aware of their options and the consequences of their choices should they be in need of similar repair work. Thanks again for your concern.
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Old 06-14-2006, 11:45 AM
  #8  
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Default Gear Rattle Revisited

Several weeks ago I posted about significantly increased gear rattle in my '89 911 after a clutch replacement. Upon discussing it with the repair shop, they indicated they had used the "much more reliable" spring-hub disk to replace the original, rubber-hub one that I had. Peter Zimmerman replied to my post saying I should have been given the choice before the work was done. Although I agree with him, I decided at that time to just "suck it up" and live with the additional noise. As time passed, though, the noise and vibration irritated me more and more. Curvy back roads that I had always driven in 5th gear suddenly required that I shift down when powering through a curve with even the slightest additional throttle. The engine certainly was not complaining, but the gear noise and vibration were most bothersome. I finally returned to the shop and asked what it would cost to do the job over with the original style clutch disk. I am happy to report that they have agreed to do the work for me next week with my paying only a very small labor charge and the cost of the more expensive part. Some of you may disagree with me, but I think this is fair of the shop. I should have informed myself more about the increased noise level with a spring-hub clutch before taking the car in. Had I been given the choice, I probably would have opted for the spring-hub disk simply because of all the bad things I've read about the rubber-hub ones the past 20 years or so. In retrospect what I should have done first, I think, is to find out just how much more noise and vibration I'd be getting with the spring-hub clutch in a G50 car. I'm posting this message not only as an update to my situation, but to thank Peter Zimmerman for his insightful remarks and to suggest to anyone else who is about to have a clutch replacement that they decide in advance which clutch they want installed. I'm sure there are many owners who would be more than willing to tolerate the extra noise, etc. for a saving of about $300 in the cost of the disk. On the whole, though, the advantages of the spring-hub one, I'm afraid, have been greatly over exaggerated.
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Old 06-14-2006, 12:00 PM
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Thanks for the info, experiences & point of view Joe.

I suspect with 66k on the clock now I'll be looking to the first clutch swap within the next 18 months or so.
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Old 06-15-2006, 04:25 AM
  #10  
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umm.. sorry to jump in with, maybe a silly question. What is the advantage of the spring clutch disk over the rubber clutch disk? Knowing about the noise.
Thanks.
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Old 06-15-2006, 04:33 AM
  #11  
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It doesn't explode...
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Old 06-23-2006, 12:38 AM
  #12  
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Update!! I got my car back today with the proper rubber center clutch disk installed this time. What a difference!!! Gear rattle noise is now barely evident--even when I purposely bog the engine down a bit. I'm really glad I took the car back for this "redo". The shop was very, very fair to me in all this, too. They gave me full credit for the spring-centered clutch disk and a substantial discount on the new rubber-centered unit. In addition, they did the job for 1/2 the normal price for labor. I'm pleased with the shop and I love my 911 again.
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Old 06-23-2006, 09:44 AM
  #13  
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Thanks for the update Joe. As I now have 62K on mine, I'll be facing this sometime soon and I've definitely learned something from this thread. BTW, which shop do you use?

Keith
'88 CE coupe
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Old 06-25-2006, 01:37 AM
  #14  
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The G50 is incredible, and I have to believe this is not ideal. I have not ever heard/felt the symptoms you mention, and I run the spring centered disc. It has exceeded my expectations over the years. I had the fluid changed last week.

I am glad to hear yours is better.

Has anyone mentioned changing the fluid to help, or it may be a synchromesh?

Regards,
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Old 06-25-2006, 08:33 AM
  #15  
Joe Rose
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Mine really is perfect now--no perceptible gear rattle even when sought after. As for fluid change, yes, I've recently done that. As for a synchronizer, no the transmission works too well for one to be faulty. In my case it was clearly the fault of the spring-centered clutch--the very reason Porsche switched to a rubber hub. I cannot explain why you don't seem to have any gear noise with your spring centered disk--perhaps you're just more tolerant of it than I am.
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