The invention relates to a hydrodynamic coupling having two blade wheels, namely, an outer wheel and an inner wheel, The hydrodynamic coupling also has a coupling shell. The invention provides that the inner wheel and the coupling shell each have one hole and the holes are situated on the hydrodynamic coupling and can be moved into positions that are aligned with one another when the inner wheel and the coupling shell are rotated. The hole of the coupling shell is larger than the hole of the inner wheel. A measuring pin for passing through the two holes.