2002 450es front diff oil?

Howdo guys. The front diff on my 02 450es (with selectable front axle engagement) is it a Limited Slip Diff ?
I've not seen confirmation it is but I've heard differing opinions. My concern, following an oil change prior to doing a ride at the beginning of the year all looked fine, no metallic evidence in the old oil, it was clean & on the level. Good oil was used in the refill. During the ride when it was being pushed hard it became apparent a bearing type noise was developing from the diff? The wheel bearings are brand new by the way!
I've heard some say unless 'additives' are introduced during a refill noises can start to be heard. One guy reported a similar story to my own & after adding a particular LSD treatment the noise disappeared. What oils and/or treatments can be recommended? Many thanks.
Chalkster