W204 C Class 2008/9 5 speed auto transmission
 

Hi, looking for some assistance with a very noticeable "whining" noise that I get intermittently every time I drive my car (which is otherwise a beauty). It happens in every auto gear, and whether I use "C", "M" or "S" modes and at most speeds. Clearly more noticeable when at 30 - 45 mph as less road noise etc.

Have had car from new, always serviced to schedule by MB dealer; just serviced this month by MB Gatwick. The problem has been there for a long time and no dealer will commit to either hearing it or just saying that its "normal". It isn't normal, I've been in enough other MBs to know that. Transmission shifts OK and is otherwise fine. Do more slow speed driving now and noticing it more and more. Would a complete flush and refill plus filter help? Help please.

anyone?

Does it happen from cold or only after driving for a while?

The two common causing of whining from a late 722.6 (5 spd) is a blocked oil filter or noisy oil pump. (both noises are from the oil pump).

A blocked filter will whine mainly after driving for a while (20-30mins+) and will get significantly louder at higher rpms. The noise will usually no be audible for first 5-10mins at least after a cold start. The slower you drive the longer it will take to be noticeable. An transmission oil and filter change will solve this one.

The noisy oil pump will usually be audible at all times, it may change a bit with temperature but wont get significantly louder at high rpm. I've only seen a few of these but they seem to be more common in later gearboxes than early ones. An oil change wont help this one, Transmission R/R and oil pump replacement is the fix.

You may have another issue, it may be a A/C, P/S or engine whining that may sound like the transmission but these are the 2 common transmission whines.