  We investigate low energy implications of string loop corrections to
supergravity couplings which break a possible flavor universality of the tree
level. If Supersymmetry is broken by the dilaton $F$-term, universal soft
scalar masses arise at the leading order but string loop corrections
generically induce flavor-non-diagonal soft terms. Constraints from flavor
changing neutral currents (FCNC) and CP violation then require a large
supersymmtery breaking scale and thus heavy gluinos and squarks. If
Supersymmetry is broken by moduli $F$-terms, universality at the string tree
level can only be guaranteed by extra conditions on the K\"ahler potential. A
large hierarchy between the gluino and squark masses ensures that FCNC and CP
violation constraints are satisfied. If the soft scalar masses vanish at the
string tree level, the cosmological problems related to light moduli can be
evaded. However, generic string loop corrections violate FCNC bounds and
require very heavy squark masses ($\approx 100\, TeV$).
