w123 230ce creaking noise in reverse

[emerty]

Hi,

I've got an 81 w123 230ce which has 201k on it. runs superbly, apart from when reversing at low speeds i get an occasional abrupt creaking kind of noise from the rear.

Could this be the diff? if so, is it worth changing the diff oil or should I get it checked by a mechanic?

Thanks in advance