W210 722.6 transmission fluid question

[smjfreeman]

Hi all!

I posted a while back about an awful droning vibration through the speed range under full torque lockup on mu 1997 E320.

I had the fluid changed at a Merc dealer a few months ago now... and up until yesterday the car has done really well. Droning virtually gone.

Yesterday, the droning returned.

Looking at the invoice, they only changed 3 litres out of the box, instead of the whole amount... (but they did do the filter and seal!). they also told me the tranny was in a good state, no metal lumps in the pan.

Could it be possible that the old oil has tainted the new over the last few months?

I have been looking at the forums here, obviously... and wondered if anyone has had this experience at all? Before you enquire about the radiator - it is not contaminating the transmission fluid with glycol.

The trans shifts perfect, the droning is only felt in full torque lockup under light load. ECU change didnt help either. That was tried too.

Because only 3 litres has been changed, I'm keen to do another change with the proper tools and oil. What is the TOTAL capacity of the 722.6? According to this forum, it varies between 5.5-7.5 litres.

Finally, I'm keen to try this excellent procedure here: http://www.peachparts.com/shopforum/showthread.php?p=1119234#post1119234

However, I dont think my 1997 E320 sports that torque converter drain plug. Must have been an option!!!

Thanks for any advice you can give..

Mike F