I have ran Royal Purple in my tranny for 15k and have been happy. I am gonna try Scottys Cocktail when I change it again, but I have not had any grinding issues like some report with the use of Royal Purple.
As for the above poster, Royal Purple engine oil has been great in my car. This info is not out of my head it is based on samples sent to Blackstone Labs, so I am not sure why you say it shears quickly