Detection of an exhausting clutch in a neutral idle-equipped transmission

A transmission assembly for a vehicle having an engine and a torque converter having a turbine, the transmission comprising:

• a transmission having:
• a plurality of rotating clutches and a plurality of braking clutches, wherein the plurality of braking clutches includes a designated neutral idle (NI) clutch;
• at least three gear sets that are configured, via actuation of at least some of the clutches, to establish a plurality of different operating states of the transmission, including an NI state that is entered when the transmission is in a drive state and the vehicle is stationary;
• an output member that receives an output torque from one of the plurality of gear sets for propelling the vehicle;
• and
• a controller configured to:
• calculate a reference slip error as a function of a speed of the engine and a speed of the turbine;
• detect when the designated NI clutch is exhausting fluid while operating in the NI state using a function of the reference slip error;
• and
• execute a control action with respect to the transmission when the NI clutch is detected as exhausting fluid.