Yes, I did as online manual says.
I discovered the length of left end in the pic between the case is a little bit shorter than the stock and this is how the friction happens. Maybe the case is a little bit thick than the stock or the overall length (in the dimension of output shaft) of the diff inside is shorter the the stock. I also discovered there is gap in the output bearing housing between the bearing and the case. It means I may need put some shims to fill the gap up.
I don't mind to do mod. but not so much as I expect when I bought this.