Abstract

A modification to an automatic transmission having a transmission brake, especially applicable to the TurboHydramatic 400 transmission, allowing for fast, consistent release of the transbrake. The reverse servo cover is modified to add a pressure release passageway communicating with the inside of the reverse servo cover and dumping fluid into the transmission pan. The passageway is selectively blocked by an electrically operated solenoid having a shaft or needle fitting into a seat, so that when the solenoid is powered, the solenoid shaft or needle fits tightly into the seat, preventing the flow of hydraulic fluid from the inside of the reverse servo cover. When power is removed, the pressure of the fluid instantly pushes the solenoid shaft back from the seat, dumping pressure from the reverse servo nearly instantaneously.