Hi Jon,
Thanks for posting. I don't know how it is on other campuses, but on mine, our DZ chapter and the Phi Delt chapter didn't have a "special" bond, per se. Of course we all know the history of Dr. Benton helping to form our Alpha chapter at Miami University!
I don't know if my chapter had more interaction with Phi Delt in the years before I pledged, but when I was there, the Phi Delt chapter was struggling and lost its charter about a year after I joined DZ. The majority of the guys that I knew were really great, but the chapter was very small and on academic probation constantly. I think that may have led to the dispersement of the group.
I hope that they are able to recolonize sometime in the near future. The school could use another good fraternity.