Chris;104741 wroteI seem to recall diff issues on the newer style XC70s like this, mentioned on the forum if you search. Some people have had success with reasonably priced rebuilds by avoiding dealers. Something to factor in to negotiations.
Rear diff gets noisy bearings
From making noise to failing can be over 200,000km though as they are a really good design
Flushing the diff fluid every 5 years or 50,000km seams to keep them going forever
OR...
Just remove the drive shaft and rear CV's and live with a FWD with better fuel economy