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Help! Hard knock after RS clutch/flywheel upgrade

Hello everyone!

I just fitted a RS clutch/flywheel kit to my MY94 993 Carrera 2 and when I run the car (idle) I notice a very hard knock around gearbox area.
If I press the clutch, the knock disappears.

The gearbox was also fully rebuilt but I don’t suspect the noise comes from it because we have successfully rebuilt some with any issues.

Does anyone ever experienced this and knows a possible cause?

I have already taken the gearbox from the car, disassembled the clutch mechanism, clutch and flywheel with any evident wear or trace on this parts that can lead me to a cause...

Thanks in advance for any help
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Last edited by AlexJ; 11-29-2018 at 09:58 AM..
Old 11-29-2018, 09:56 AM
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My '96 does the same thing.

It's caused by the RS clutch.

The dual mass flywheel you removed is a very heavy instrument that is designed to reduce the noise.

Hopefully you will come to enjoy the noise!
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Old 11-29-2018, 10:41 AM
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Im pretty sure its “clutch chatter.”

Common issue when these cars run solid trans mounts or lightened/rs flywheel.
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Old 11-29-2018, 10:45 AM
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Thanks for your messages.
So, I should assume this is normal and nothing bad will happen to the new components?
And yes, I also fitted hard mounts to transmission and engine.
Thanks again for the feedback.
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993 Carrera 4 1995 artic silver, 993 Carrera 2 1996 Black
911 SC 1982 Linen Grey Metalic
RS clone Tarmac rally car (under construction)
911 T 1968 - waiting for better days
911 T 2.4 1972 SOLD
Old 11-29-2018, 05:15 PM
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Quote:
Originally Posted by AlexJ View Post
Hello everyone!

I just fitted a RS clutch/flywheel kit to my MY94 993 Carrera 2 and when I run the car (idle) I notice a very hard knock around gearbox area.
If I press the clutch, the knock disappears.

The gearbox was also fully rebuilt but I don’t suspect the noise comes from it because we have successfully rebuilt some with any issues.

Does anyone ever experienced this and knows a possible cause?

I have already taken the gearbox from the car, disassembled the clutch mechanism, clutch and flywheel with any evident wear or trace on this parts that can lead me to a cause...

Thanks in advance for any help
Caused by the single mass flywheel; now you know one of the things a dual mass does for the car...…………...
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Old 11-30-2018, 06:18 AM
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Originally Posted by JFP in PA View Post
Caused by the single mass flywheel; now you know one of the things a dual mass does for the car...…………...
Now I know! Thanks!
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993 Carrera 4 1995 artic silver, 993 Carrera 2 1996 Black
911 SC 1982 Linen Grey Metalic
RS clone Tarmac rally car (under construction)
911 T 1968 - waiting for better days
911 T 2.4 1972 SOLD
Old 11-30-2018, 07:52 AM
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A good read, if you’re interested.
http://www.techtalk.ie/wp-content/uploads/2018/01/LuK_tec_brochure_dmf_de_11_2017.pdf
Old 11-30-2018, 02:34 PM
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540964, Great read, great info. Thanks!
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Old 12-03-2018, 06:04 PM
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Now in 993 land ...
 
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Oh man - I wish you would have posted before taking things apart! Mine does this intermittently as well. It had the LWF from the PO and it didn’t change after a new clutch / trans rebuild either!

G
Old 12-07-2018, 09:06 PM
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Interesting... is the loud knock noise, consistent? Any way to hear it in a video?

Why would the 964 with a single mass flywheel make a knocking sound, when earlier cars with a SMF didn't? (I am attempting to learn something here).
Old 12-08-2018, 01:32 PM
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<--- keeping stock flywheel, but I don't race at all
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Old 12-11-2018, 10:57 AM
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Now in 993 land ...
 
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Quote:
Originally Posted by mikedsilva View Post
Interesting... is the loud knock noise, consistent? Any way to hear it in a video?

Why would the 964 with a single mass flywheel make a knocking sound, when earlier cars with a SMF didn't? (I am attempting to learn something here).
I would not describe it as a knock. Most the time it is a shattering sound. Sometimes it is a loud click - definitely not something like a rod knock or pinging.

I do not quite understand the mechanics behind it... (edited after reading the LuK article ...) I just recall searching or asking about it here when I bought the car and was freaked out.

G
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Last edited by aigel; 12-11-2018 at 11:19 AM..
Old 12-11-2018, 11:06 AM
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The article from LuK explains a lot
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Old 12-11-2018, 11:08 AM
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Quote:
Originally Posted by aigel View Post
I would not describe it as a knock. Most the time it is a shattering sound. Sometimes it is a loud click - definitely not something like a rod knock or pinging.

I do not quite understand the mechanics behind it... (edited after reading the LuK article ...) I just recall searching or asking about it here when I bought the car and was freaked out.

G
Marbles loose inside the tranny!!, normal.
Old 12-24-2018, 10:29 AM
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Back in the uk I fixed this noise successfully .
I simply installed a cat by-pass straight into a fabspeed dual outlet rear .
Problem solved .
Old 12-30-2018, 09:26 PM
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Originally Posted by ian c2 View Post
Back in the uk I fixed this noise successfully .
I simply installed a cat by-pass straight into a fabspeed dual outlet rear .
Problem solved .
I had that setup for a month before I baffled the outlets, it set off car alarms and rattled windows!
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Old 12-31-2018, 10:48 AM
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Quote:
Originally Posted by AlexJ View Post
Hello everyone!

I just fitted a RS clutch/flywheel kit to my MY94 993 Carrera 2.
Just curious, but what made you go for it over the stock set-up? Was the original worn out and slipping?


Are you on the track most of the time?
Old 01-04-2019, 03:05 AM
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Did you happen to also change the gearbox mount? Recently changed mine with the original Porsche Classic part 964.375.055.81 in a preventive "while the gearbox is out of the car" attempt. Following the reassembly I was under the impression something is broken or the drivetrain is in contact with the body. Upon further investigation we realised that the new Porsche part has been re-produced by Porsche with way too hard rubber insert (almost as hard as concrete) and had to source a used gearbox end plate with a used (but still good) mount still pressed in.
Old 01-06-2019, 03:45 AM
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Quote:
Originally Posted by Nikolaus View Post
Did you happen to also change the gearbox mount? Recently changed mine with the original Porsche Classic part 964.375.055.81 in a preventive "while the gearbox is out of the car" attempt. Following the reassembly I was under the impression something is broken or the drivetrain is in contact with the body. Upon further investigation we realised that the new Porsche part has been re-produced by Porsche with way too hard rubber insert (almost as hard as concrete) and had to source a used gearbox end plate with a used (but still good) mount still pressed in.
That is what I did! Changed the hard rubber mounting by the original one, and 80% of the noises disappeared!
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993 Carrera 4 1995 artic silver, 993 Carrera 2 1996 Black
911 SC 1982 Linen Grey Metalic
RS clone Tarmac rally car (under construction)
911 T 1968 - waiting for better days
911 T 2.4 1972 SOLD
Old 03-01-2019, 04:45 PM
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Curious why my 964USA Cups don't exhibit this rattling or knocking? I'm assuming the USA Cup has a SMF?
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Old 03-15-2019, 09:45 AM
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