as far as i know, each wheel of the turbo is balanced, so the compressor wheel is balanced seperatley, and then the turbine wheel and shaft assembly is balanced. Hence when you take them off and put them back on in totally different positions, they don't turn to ---- because they're both balanced seperatley. Although i've heard that somet turbos are balanced as a whole assembly and weight is removed from the shaft nut, and when you mis align things, it turns to ----. Now i could be completley wrong but i think it probbaly holds som truth since there are people on here that are going 15K+ miles with homemade rebuilds. just a thought