Here's one for the Merc experts amongst us:

My dad's 1999 E240 has developed a nasty drivetrain whine. We had it running on a ramp and the noise seems to come from the differential.

Now is it possible to rebuild one yourself or is it better to get a 2nd hand unit?

Also if you know anyone breaking a W124 or W210, please let me know. All the places here try to charge me an arm and a leg for what essentially is a set of gears and bearings.

Thanks in advance!