Does anyone know how to service the differential on a 1996 S420 ?

I am looking for instructions on servicing the rear differential on a 1996 S420 ?

Has anyone worked on this job ?

How about the fluid ? Is it the same as the transmission fluid?

I suspect you didn't get any response to your first posting because you didn't specify what you meant by "service". It helps to be specific about what you need to know.
If you're simply talking about changing the diff fluid, there's a drain plug on the bottom and a fill plug on the side. If you do a search you'll find the procedure. Just make sure you loosen the fill plug before you remove the drain plug. The fill plug is pretty tight if its never been out and you don't want to drain the fluid just to find out you can't remove the fill plug!
As I recall, the fill plug requires a 14mm male hex adapter. Be sure to put the car on a secure lift or stands.
No, the diff fluid is NOT the same as the trans fluid. Check the books and get the right diff fluid.

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KenP

1996 S500 W140 Coupe

The gasket around the differential is a bit wet. So I need to replace the gasket and then ofcourse I have to refill the differential.

So that's was the reason for the query.

Anyway thanks for the reply it does help to know the sequence of work.

Are you sure that this is not coming from the vent at the top? Many 126 differentials are always coated by a light coating of oil because of fluid that escapes from the vent. Im not sure about the 140. You may not need a gasket at all. Might want to check into this before ripping into it.