rushing as junior transfer

Leading up to college, I always look forward to greek life. The university I picked, however, has week greek life and I never really connected with any sororities. I will be transferring to UNC next fall, where I know no one, and I hope to join a sorority there. I have heard that UNC requires sororities to accept so many juniors to fill a quota, is this true? If so, will this help in the rushing process? I am hoping for a top tier sorority. How accepted are new members that are juniors? Thanks!