Hi!

I have a 2009 Volvo c30 with the m66 transmission. Since I bought the car from a very shady place, I've had multiple issues with it, and have been repairing them myself for the most part. I've been getting a knock from the transmission. The noise happens, and is most audible, when the car is in neutral, without the clutch pedal pressed. If the clutch is pressed in, the noise goes away. Initially, I thought the noise would be the input shaft, so I took the transmission out of the car and planned to pop it open to inspect. However, I realized today that this might not be the issue. The throwout bearing/slave cylinder assembly has large grooves worn into it from the pressure plate, and looks very worn. If the car is rolling with the clutch in while in gear, the noise doesn't seem to happen; In this circumstance, I feel like the input shaft should be spinning too. Is it more likely to be the throwout bearing? I'm not a mechanic, yet, and all I've taken is an intro class.

Thanks for reading all that. If you don't want to, TLDR:

Transmission knocks when clutch engaged in neutral, while rolling or parked. Clutch disengaged in gear while rolling, transmission does not knock. TOB looks very worn. Open up the transmission, or is the TOB likely the problem?

P.S. I plan on replacing the TOB, pressure plate, and clutch already. Maybe the flywheel too, depending on how it looks. Haven't finished the teardown yet.


Image of the throwout bearing. Large notches worn from pressure plate.