Help troubleshoot 904? Slipping at higher RPMs

Thanks guys!

I know i will never get rich building these things, But if im taking money to build someone a trans? I want it right for them. And don't like seeing them come back unless it many many years later? lol Lost one friend a few years ago over a 727 I built for him. It worked and shifted fine. But had a noticeable whine going down the road. Figured i missed a bad bearing in one of the planets? Even offered to pull it back out and go back though it for him. 2 things still bothers me over that. It had the whine, And i lost a friend over it. Lesson leaned... Not worth losing a friend or a customer over $$$.