Dalet: The raddle chain does the same thing as the shoe augers on your JD 4400. The raddle carries the grain/trash up from under the cylinder. The straw walkers have a pan made in the bottom of them to shake the grain forward. If you go down a steep hill the raddle chain will plug and if you shell up a steep hill the straw walker pans can get full and walk all the grain out the back.
The augers where a big improvement over the raddle chain. I think this one thing really jumped JD ahead in the combine market around here.