I have loaded dead D7s quite a few times,  if the tractor moves and is free just back your trailer up square with the cat and have it pretty centered with the steering clutches engaged,  I used a big heavy tow bar with eyes on both ends and hooked it to the drawbar of the dead cat and in my case I used another D7 with the drawbar pinned and hooked to my tow bar  and just pushed up on my lowboy and had Very little trouble. A piece of cake, a D4 should be easy!    17afarmer