Once upon a time, there was a web site called UC Statfinder that allowed generating custom tables, such as one listing GPA in the first year after transfer for students transferring from California CCs to UCs with small ranges of prior college GPA. Those particular tables indicated that those with 3.8-4.0 GPA at CC prior to transfer typically averaged 3.4-3.7 GPA in the first year after transfer (depending on campus). This 0.2-0.5 GPA drop did shrink at lower GPA levels, disappearing at around the 3.0 level (of course, 3.0 transfer applicants are only likely to be admitted to the least selective campuses, not campuses like Berkeley or Los Angeles, most of whose admitted transfers were in the 3.8-4.0 range).