Mercedes-Benz W211 rear axle oil and differential leak
What rear axle oil does the W211 differential take?
The differential needs an MB 235.7-approved synthetic oil, which has replaced the older mineral oil (235.6). The most common recommendation is viscosity 75W-85. Confirm the exact oil and quantity from the owner's manual or the Mercedes approval list.
How do you check and fill the differential oil level?
On the side of the differential there are two hex plugs, through which the oil is drained and filled. The oil level is correct when the oil reaches the edge of the upper plug. The rear axle oil should be checked and changed at intervals, because differential leaks are common.
Why does the differential leak oil?
A common cause is a blocked breather. The pressure inside the differential rises and the oil is pushed out at the weakest point, often the propshaft seal. A blocked breather should be checked before you replace seals.
Does an oil change remove differential whine or noise?
Not on its own. The noise can also come from the propshaft support bearing or a mount, so an oil change alone does not necessarily help.