[greg968CAB]

SO a couple of days ago, I go out to my car and start it. Everything was normal except for a knocking sound when I went from Park into Reverse. The engine appears to still be stable on its mounts. The Tiptronic appears to have correct fluid level. The engine still performs normally. The Tiptronic still shifts seamlessly whether in Auto or manual mode. I have gone into the engine bay looking for anything lose and have found nothing. The AC appears to still be mounted and the belt seems to still be properly tensioned. I checked the distributer and alternator to see if they might be lose.



The car still drives normally. There is no loss of power. The steering is still ticht. The wheels all seem to still be soilidly attached and the tires still look like they are new.



The sound does not appear when the car is in Park or neutral.



The sound does appear briefly when the starter is engaged.



The sound does not seem to be related to engine speed.



The sound will appear when the car is in a forward gear and stopped or in reverse and stopped.



The sound itself sounds like a diesel engine knocking badly.



In addition the sound is similar to the sound that the engine tins on a VW beetle made when they were loose.



It is utterly driving me crazy at this point.



Does anyone have an idea as to a possible cause or a way to triage this?

Oh and to be a bit more clear, once the car begins moving and gets above 10 MPH the sound disappears.

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[flash]

blown flex damper

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[968Syncro]

That is what I was going to guess also. If that is it, not cheap, hate to bring bad news. It was replaced on my car by the previous owner, $900 for the part, $1,530 for labor.



Flash, any idea on a diagnostic for this possible cause, how could that root cause be confirmed without taking things apart?

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[flash]

not sure if there is a side cover or not (as there is on the 6 speed)



if there is, you would be able to see the 2 yokes banging into each other



for those who have never seen the parts, imagine a pair of drive shaft yokes with a rubber disk between them that all 4 of the "ears" went through, and that disk essentially keeping the yokes form contacting each other. when the disk goes away, they slam into each other with torque of the engine and engagement

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[968Syncro]

Thanks, it got me curious and took a look at the PET. (PET_E_968_KATALOG_Update248.pdf). Illustration 310-00 on page 78 of 351 shows these parts, including the "damper". The housing looks about the same as the clutch housing, and the illustration shows a "cap" item number 18. That most likely is an inspection hole to take a look at the damper.



   

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[968rz]

If you're good you can see the damper through the hole in the bell housing (on the driver side) that would be for the clutch slave, it takes some looking but I was able to verify mine was torn via this hole without dismantling anything.

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