[Eljaro]

Hello Toni,
the two supports which have the holes where the fulcrum shaft goes through are bolted to the differential, and have shims . If you find that you need a lot of pounding to get the shaft through it may be that the hole for the fulcrum shaft in the frame is not exactly aligned with the ones on the differential. You can unbolt the shaft support from the diff and take out or add shims to align the holes ( not too many shims though, since these are there to align the rear end with the frame.
You will see that the shafts will go through easy with just a nylon mallet.
If they go with great difficulty they are probably bending their way through the three holes. Stress and breakage will result.
Good luck
Stefan