Gauge coupling constant unification with Planck scale values of moduli

Convergence of the standard model gauge coupling constants to a common value at around 2 × 1016 GeV is studied in the context of orbifold theories where the modular symmetry groups for T and U moduli are broken to subgroups of PSL(2,Z). The values of the moduli required for this unification of coupling constants are studied for this case and also for the case where string unification is accompanied by unification to a gauge group larger then SU(3) × SU(2) × U(1).