154 by causing both valves 164 172 to be concurrently open the first area 136 is arranged such that pressure in chamber 150 acts on the first area 136 to overcome the bias of the belleville spring 134 and move the piston 132 axially into engagement with the plates 124 and discs 128 similarly the second area 140 is arranged such that pressure in chamber 154 acts on the second area 140 to overcome the bias of the belleville spring 134 and move the piston 132 axially into engagement with the plates 124 and discs 128 pressurizing only one of the chambers 150 154 results in less piston force and therefore less torque capacity of the torque transmitting device 120 than pressurizing both of the chambers 150 154 a given amount of pressure error with only one of the chambers 150 154 pressurized results in a smaller amount of torque disturbance than the same amount of pressure error subjected to both chambers 150 154 torque transmitting devices 116 and 112 are similar to torque transmitting device 120 in having respective pistons with separate chambers that may be separately and independently pressurized by controller 180 as shown in fig3 relatively high torque capacity is required from torque transmitting device 116 for the reverse and first speed ratios and relatively low torque capacity is required from torque transmitting device 116 for the second seventh and eighth speed ratios relatively high torque capacity is required from torque transmitting device 120 for the reverse first second and third speed ratios and relatively.