Fluid Pressure Directed in Preparation for a Power Loss Situation

Default Disable Solenoid 

The default disable solenoid is energized on allowing ON/OFF SIGNAL (19) fluid to enter the FEED LIMIT - LOW (15) fluid circuit. FEED LIMIT - LOW (15) fluid is directed to the default disable valve, feed limit valve - low, ball check valve # 1 and ball check valve # 2. The default solenoid controls the default disable valve, which controls the system to pressurize clutches through their exhaust ports to hold either gear in a power loss situation. Default disable solenoid has to be on to keep out of default. Default in Reverse gives Reverse, while default in Drive gives 7th gear initially. The vehicle will restart in 2nd gear after a key cycle or a Drive-Reverse-Drive state change, as determined by the Drive Select valve's latch state. Drive and reverse oils are controlled by a manual shaft. There needs to be a minimum of 450 kpa line pressure to result in a gear under default. This is due to the spring pressure of the default disable valve.

Feed Limit Valves 

The boost ball system uses two additional pressure circuits called FEED LIMIT - LOW (15) and FEED LIMIT - HIGH (16). These circuits control the pressure at which the circuit boosts to line pressure. The FEED LIMIT - LOW (15) circuit controls the boost balls for clutches 1-2-3-4-5-6 R and 1-2-8-9-10 R, while the FEED LIMIT - HIGH (16) circuit is used for clutches 2-3-4-5-7-9-10 and 1-2-3-4-6-7-8-10 R. The following is the range on feed limit pressures at which boost can happen. FEED LIMIT - LOW (15) boost range is a minimum of 660 to a maximum of 825 kpa. FEED LIMIT - HIGH (16) boost range is a minimum of 1000 to a maximum of 1252 kpa.

ETRS Valve 

The default disable solenoid is pressurized and moves the ETRS Mode Valve, whose position is read by a switch. This allows line pressure to feed Out of Park oil which shifts over the Park Servo valve, and its position is recorded with two position switches.

Park Servo Valve 

The Park Servo valve is held in the out of park position by the Park Inhibit Solenoid. The park inhibit solenoid is only designed to hold the trans out of park against the park servo spring, so any pressure at the return to park end of the servo can cause the park inhibit solenoid to be overcome.