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      09-06-2019, 11:13 AM   #1
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Clunk noise when disengaging clutch while engine is applying torque to drivetrain

y'know the noise I'm talking about? it often happens when you're in 2nd or 1st gear, and the car is engine braking and you press the clutch pedal.

I read somewhere that this is normal, but what causes this noise?
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      09-06-2019, 08:29 PM   #2
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Not sure if links to other forums are welcome here or not.. so just copy-pasting it

Quote:
"I'm with BMW of North America, LLC. The M3 is a refined version BMW's race cars. It is designed to provide optimum power and performance in a street legal package.

In order to transmit engine torque to the rear wheels instantaneously, without any time lag, the whole M3 power train was designed with maximum torsional rigidity. To achieve this maximum torsional rigidity, the flywheel mass and its damping capability has been reduced to a minimum.

As a result, during an abrupt torque transfer (e.g. 1st to 2nd gearshift at low engine speeds) the driver can receive an acoustic feedback, which can be interpreted as a "clunking or rattling" noise.

The acoustic feedback characteristic is not a symptom of a failure, and does not compromise long-term reliability of drivetrain components (clutch, transmission, differential), nor does it adversely affect performance of the vehicle.

If you have any questions, you can phone us at 800-831-1117. "
My take is that the clunking noise comes from the DMF when its springs gets compressed / decompressed suddenly.
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      09-09-2019, 05:06 AM   #3
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Hmm I don't think it's normal at all. Mine never used to do it, now does it all the time. How many miles on the car. Refurbing my driveshaft due to this. Guibo, hanger and most likely culprit , the CVJ.
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      09-20-2019, 04:14 PM   #4
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That snippet sounds a lot like sales BS. "acoustic feedback that can be interpreted as a clunking noise" lol. it is definitely a clunk.

Also I have a lightweight single mass flywheel so it's definitely not just the DMF.
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      09-20-2019, 09:24 PM   #5
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Well.. I had a worn out DMF replaced on my previous BMW and it did improve the sound during gear switch.

But since you don't have DMF here is another (probably even more common) clunk generator

PS: and I assume you've checked axles and guibo already
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      09-21-2019, 10:08 PM   #6
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Could be clutch disc spline wear.
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      09-22-2019, 11:09 PM   #7
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Hmm. I accidentally deleted something here??
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Last edited by Vanne; 09-24-2019 at 12:53 AM..
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      09-23-2019, 12:02 AM   #8
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Why do you say most probably the CVJ?
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      09-23-2019, 04:27 PM   #9
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Did you watch the vid vt100 posted?
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      09-23-2019, 04:33 PM   #10
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Yeah, I am just wondering why you think that is the most likely cause of all the possibilities. I don't remember my wheel wiggling like that last time the car was on a lift - but I will try the wheel wiggle test more vigorously next time the car is on a lift and report back. Might be a while since I don't have convenient access to a lift.
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      09-24-2019, 12:52 AM   #11
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Well that list is in a cheap to expensive to replace parts/labour.

Only reason I am saying CVJ, is that is because that's what mine was/is. Which sounds EXACTLY like what your describing.
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