The on-coming clutch of an automatic transmission is filled for a fill time determined from empirical data embodied in look-up tables which relate the effects of pump speed and fluid temperature on the fill time. The fill time is determined for a baseline clutch and then multiplied by a volume ratio for a particular clutch. The effect of fluid temperature on leakage is tabulated and used with the pump speed to determine the effective pumping speed. The effects of fluid temperature on viscosity and oil flow rate are determined and used to adjust the base fill time for low pumping speeds. The fluid retained in a clutch cavity from a recent application and not fully exhausted is also taken into account.