W203 Differential humming?
 

When im on the highway and im at a pretty constant speed my 2001 C320 makes a slight high pitch humming noise coming from what seems to be the differential? Anything i can check, or any ideas?

I had a Jaguar with the same symptoms and I took it back to the dealer. They lubed all the fittings under and changed the fluid which solved the problem. Go to your local dealer and ask them

There is a dealer technical bulletin on cars below 022063(last six # of VIN). Installing a shim (2.5MM) between the differential & differential mounts is the fix!

My VIN is # WDBRF64J81F083850

Is there a possibility that the shim could be the problem even though it did not fall in the numbers?

What else could it be, besides teh Shim?

My best bet would be to go to the dealer and ask them to replace the shim and if they refuse, you should insist on the job getting done for free. Try having the bearings, ball joints, differential checked out to see if there is a prob back there

I am pretty sure the car is out of warranty.. so i dont think they will

The high pitch humming noise is usually caused by the pre-load not within spec. If plan on keeping your Mercedes, you will be money ahead if you paid for the dealer to check your differential to see if it needs adjusting. It is far cheaper than replacing the differential. If you purchased your car at the dealer they might give you a discount - it doesn't cost anything to ask.

Can you give me the Bulletin # so I can go and address this with the Dealer??