its balanced as a unit, similar to the way you can balance a crank, flyweel and clutch together, or the inside and outside of a wheel. So i always ensure they go together in the orentation the come appart. Ive done one before without lining them up, cos i did the exact thing you did first time round! put it back together, but you could clearly hear the turbo vibrating as it spooled at a set speed, and it smoked! Done several since with no hassle though.