i had this happen to me when on some pretty steep inclines loading material from a loading dock, what i did was put it in park and engage the emergency break almost at the same time, what you should probably try doing before engaging park is putting it in neutral while holding the break down then engaging the emergency break, letting go of the break pedal let the truck rock forward or back, then engage park, this way the weight rests on the emergency break and not the transmission, i never had the problem with it being hard to shift into reverse after doing this, probably puts a lot of pressure on the breaks but better then the tranmission right, hope that helps
