It could be Salisbury with a Quaife LSD, but the Morris oil does have friction modifier so it should be fine. It takes a long time to drain by the way - and remember the golden rule...... take the filler plug out first, before you drain it. the Salisbury has a drain plug in the bottom of the casing. The BTR drains through one of the rear cover bolts.
A bit more detail here.....
http://www.talkmorgan.com/ubbthreads.php/topics/30883/1
