From Freleiten, cross the river and follow the track down the valley for about 2km until Vögerlalm.

Head E uphill (either along the forest road, or along the more direct path) until around 1700m where the Eichhornruhe hut is.

Go up the steep part just next to the cliffs until 2100m, then head south for a bit, across the stream, and the Schwarzenberghütte is slightly higher up behind the moraine.  

From the Schwarzenberghütte head E, weaving between the moraines, reach the Hochgrubekees.

The Gruberscahrte is very steep on the north side (+45 degrees) with big cornices and a bergschrund underneath, better to reach from the south side (left when going up)