My bora has been making horrible clicking noises when reverse parking and doing sharp turns / ESP comes on / and it 'skids' does a sort of 'bunny hop'.

Mechanic says it needs a new rear diff. Or at least the pump in the diff might need looking at.

How much (roughly) would this set me back ? The mechanic said he might be able to use the diff from an Audi S3 in mine. Would that be OK or is Bora specific diff better?

I am clueless, need knowledged people to help.

cheers
gov