Mercedes: Tapping sound from transmission, commodore v6, holden commodore

Question
QUESTION: Dear Rob,
There is a tapping sound that seems to be from the transmission and is audible only from inside the car. The tapping frequency stays constant regardless of engine revs or gear driven, even while parked and engine idling. When engine is shut off and restarted, the tapping sound disappears, but becomes audible again after about 10 minutes. The car drives fine, gear shifting is very smooth. Is the tapping sound cause for concern?

ANSWER: Kieran,
Not knowing the year, model age or mileage of the vehicle or without hearing the sound first hand these are only conjectures. It is possible that the torque converter is causing the noise. It could also be something in the climate control fan.
I would raise hood and try and isolate the location. Raise the hood start the vehicle and then immediate listen with the hood up until the tapping begins. If it is in the firewall, then the climate control may be suspect.
Good Luck
Rob


---------- FOLLOW-UP ----------

QUESTION: Hi Rob,
Actually my car is not mercedes; it is a holden commodore (V6 engine) 2006, with 72,000 miles. I couldn't find any other website except yours that could offer some answers.
On receiving your reply, I checked under the hood, and although the tapping / knocking is audible from inside the car, it is not at all audible when checking under the hood.
With the climate control fan swirtched off, the knocking is still there.
I did notice that sometimes in reverse there is a little slippage.
Even though I don't have a mercedes, I still hope you can reply and give me some insight; thanks

Best regards,
Kieran


ANSWER: Kieran
is this vehicle an automatic or strait shift?
Rob

---------- FOLLOW-UP ----------

QUESTION: Hi Rob,

It's an automatic. Also this morning I noticed a faint "jeet jeet" scraping sound in neutral, which disappeared when put into gear. Also the tapping noise is not there all the time.

Best regards,
Kieran

Answer
I would take the vehicle to an independent transmission shop for diagnostics and repairs. Have the tech check it out. If it is slipping in reverse, you may have metal to metal on the band and drum.
To delay, may be quite expensive. The transmission shop may be able to adjust out the slack.
Good Luck
Robert