Clunk from diff on full lock

[red griff roger]

Had an E46 M3 for nearly a year (55 plate), and have just noticed a sort of grinding clunk from the rear on full lock. Dealer says this is the friction plates slipping, and the fix is different diff oil. Well, I am a bit suspicious. But importantly, it is just about to run out of warranty - therefore the real question is: am I being fobbed off with a 'sawdust in the sump' type fix, and likely to get a big bill later (when it will be out of warranty), or is this, as the engineer says, a common thing? Anyone else had this, or heard of it?

Cheers, roger

[red griff roger]

Thanks. BMW is doing the service, so I will leave it to them. Relief to hear that all is OK!

roger