In some cases power mode will render the lockup torque converter ineffective. Operating a vehicle in constant power mode will not have as detrimental an effect on fuel economy as might be expected, but will however prolong transmission life. When a transmission service is carried out the oil pan is removed and the fluid is drained. However with the exception of a few model vehicles where it is not possible to drain all the fluid from the transmission and if the fluid is extrordinarly dirty the fluid added at the completion of the service will be immediately contaminated by the remaining oil in the torque converter and oil galleries of the control unit. To flush the transmission, oil flow is interrupted by removing a transmission to radiator cooling pipe.
New fluid is added to the transmission while the engine is running.