We discuss nucleon transfer and fusion reactions of
the $^{40}$Ca+$^{58}$Ni and $^{40}$Ca+$^{64}$Ni systems with the coupled-channels
approach. It is first shown that a simple treatment for the transfer in the coupled-channels method cannot reproduce simultaneously the transfer probabilities and the sub-barrier enhancement of the fusion cross sections. An alternative scheme for the transfer, that takes into account other collective states in the pair transfer channel is proposed.