Transmission shift control

Abstract

A transmission control method comprises the steps of determining whether a shift requiring an output shaft lock-up is commanded, wherein such a shift involves a first torque transmitting mechanism either being applied or released while a second torque transmitting mechanism is held engaged. The control determines whether the vehicle is stopped by one or all of the following: verifying the vehicle service brakes are applied, the transmission output speed is near zero, the engine speed is low, the oil sump temperature is greater than a calibration temperature, and the turbine speed is near zero if the vehicle is in forward drive. If the vehicle is stopped, a lock-up torque transmitting mechanism is applied prior to the shift operable to prevent torque transmission to the output shaft. When the lock-up mechanism reaches capacity, the shift proceeds by one of applying and releasing the first mechanism, while maintaining the second mechanism engaged. Once the first mechanism has one of reached capacity and released pressure below a threshold, the lock-up mechanism is released to complete the shift.

Dependencies are inferred from the claim text.