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

[Talkwrench]

No, its not a 'fob off'.
The plates can chatter on LSD's on tight turns. BMW LSD oil has the additive present but its not uncommon for a little more to be required. It is basically a friction modifier adding a little more 'slip'.
No need to change the oil though, unless you really want to! There are many additives available that cure the problem. Just a small amount is required. Jaguar dealers sell a separate additive. The likes of Red Line produce one (available from demon tweeks). If you have a genuine rally or racing supplier anywhere near you, they should have some.
These guys sell an additive that will do the job too.
http://www.gearboxman.co.uk/pslubricants.html
Plenty to choose from!

[red griff roger]

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

roger