Need help/axles with C-class

1994 C200 Right hand Drive that I own overseas. Car started having a vibration at speeds over 20mph. Replaced engine/tranny mounts and driveshaft carrier/bearing. My mechanic is now telling me that I need rear axles. I've been around MB for awhile and I've never heard of this. Can anyone offer any advice here and if all else fails, where I can find 2 new or used axles.
Thanks
KEvin