The rovibrational energy transfer processes occurring in methane upon inelastic CH4-N-2 collisions have been investigated by using time-resolved double-resonance (DR) measurements. The CH4 molecules were excited at about 1.66 mum into selected rotational levels of the 2nu(3)(F-2) state by an optical parametric oscillator pumped by a Nd:YAG laser. The low power beam of a tunable diode laser emitting around 3.4 mum was used to probe the following transitions: (nu(3) + nu(4)) <--nu(4), 2nu(3) <-- nu(3), (nu(3) + 2nu(4)) <-- 2nu(4), and 3nu(3) <-- 2nu(3) transitions. Measurements were performed in CH4-N-2 gas mixtures with various molar fractions of methane. Rate constants were deduced from the time evolution of the transient populations of the probed levels. N-2 has been found to be an efficient collision partner to deplete the laser-excited level through rotational energy transfer, with a rate constant of (13.0 +/- 1.5) mus(-1) Torr(-1) and through intermode transfer to equilibrate the populations among the states of the tetradecad, with a rate constant of (2.0 +/- 0.6) mus(-1) Torr(-1). These measurements have allowed us to determine the part played in the vibrational relaxation by intermode transfer processes, which occur between the strongly interacting states of the polyads upon CH4-CH4 as well as CH4-N-2 collisions, and by near-resonant V-V energy transfer processes coupling the tetradecad to lower polyads, which occur only upon CH4-CH4 collisions.