The transfer reaction between two nuclei in the superfluid phase is studied with the time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory. To restore the symmetry of the relative gauge angle, a set of independent TDHFB trajectories is taken into account. Then, the transfer probability is computed using a triple projection method. This method is first tested to determine the transfer probabilities on a toy model and compared to the exact solution. It is then applied to the reactions O-20 + O-20 and O-14 + O-20 in a realistic framework with a Gogny interaction.