Just had the differential resealed on my 1995 C280 with 89,000 miles by an MB dealer who charged about $500. 3,000 miles later the pinion bearing started making noise and rapidly became worse to a screaming note. I took it to an independent who indicated that the pinion seal was probably overtightened causing the pinion bearing to fail (he checked it by running it on a lift and listening with a stethascope). Bottom line was that he indicated that a rebuilt differential would be necessary at an estimated cost of $2,650. I took it back to the MB dealer who also diagnosed a bad pinion bearing and again indicated that a rebuilt differential would be necessary. They indicated part price was $2,000! At present, I am battling with them to pick up the cost since they were responsible for the failure to begin with. They indicate it is not their fault since they checked the preload on the bearing on it is within specs. My indy says that if the job was done right the differential would not have failed. He also indicates that you usually never have any problems with an MB differential and these vehicles usually go to the grave with the original differential. Right now, the MB dealer has had my car going on two(2) weeks and they still have not gotten the rebuilt differential. At least I have their 2004 ML 350 loaner while they try to get the part.

All I want to point out is that if you do not know what you are doing, you may do more harm than good and this job may be something for an experienced tech to handle.