Method of controlling clutch-to-clutch shifts for a powershift transmission

A method of controlling a powershift transmission, the transmission comprising:

• a plurality of speed changing clutches;
• a plurality of direction changing clutches;
• a plurality of pressure control valves individually connected to the clutches;
• a hydraulic pump adapted to deliver pressurized hydraulic oil to the plurality of pressure control valves, predetermined ones of the pressure control valves metering hydraulic fluid to the clutches in response to receiving a clutch command signal, the method producing a shift from a first transmission ratio to a second transmission ratio through disengagement of an off-going clutch associated with the first transmission ratio and engagement of an on-coming clutch associated the second transmission ratio, in accordance to the following steps:
• commanding a pressure control valve associated with an on-coming speed clutch to fill the speed clutch;
• thereafter
• commanding a pressure control valve associated with an on-coming direction clutch to fill the direction clutch;
• commanding a pressure control valve associated with an off-going speed clutch to reduce the clutch pressure to cause the off-going speed clutch to release in response to the on-coming speed clutch being filled;
• commanding a pressure control valve associated with an off-going direction clutch to reduce the off-going direction clutch pressure to cause the off-going direction clutch to release in response to the on-coming speed clutch being filled;
• thereafter
• commanding the on-coming speed clutch pressure control valve to gradually increase the speed clutch pressure to engage the speed clutch;
• and
• commanding a pressure control valve associated with an on-coming direction clutch to gradually increase the on-coming direction clutch pressure to engage the direction clutch in response to the on-coming speed clutch being engaged.