We report a third-order nonlinear time-domain method, coherence period (tau) resolved transient grating (TRTG), that gives accurate solvation dynamics free from population relaxation in a short data acquisition time. The validity of TRTG is established by theory and experiment. The TRTG signal is shown to follow the transition frequency correlation function by an analytic expression based on the response function theory for delta function pulses and by model numerical calculations including finite pulse, durations. TRTG is demonstrated for two cyanine dyes IR144 and IR125 in methanol by using a diffractive-optics based four wave mixing apparatus. Solvation dynamics in methanol obtained from the TRTG are consistent with those reported previously confirming the validity of TRTG.