Measurements of sub-barrier transfer reactions are reported for the systems 28Si + 64Ni, 32Si + 64Ni and 28Si + 144Nd using the recoil mass spectrometer HIRA in kinematic coincidence mode. The problem related to M/Q-ambiguity in measurements with mass separators has been resolved. Excellent mass resultion with a large solid angle is obtained by correction of the aberrations. Simplified coupled-channels calculations are carried out for these systems with transfer form factors extracted from the measured transfer probabilities. The surface vibration coupling is treated up to two phonon states with second-order coupling terms.