As vehicle speed increases, the TCM receives input signals from both speed sensors, the TP sensor and other vehicle sensors to determine the precise moment to de-energize or "turn OFF'" the 1-2 shift solenoid (SS) valve, and to energize or "turn ON" the 4-5 SS valve.

Direct Clutch Applies

1-2 Shift Solenoid (SS) Valve: The 1-2 SS valve is de-energized, blocking feed limit fluid from entering the 1-2 signal fluid circuit and 1-2 signal fluid pressure exhausts through the 1-2 SS valve.

3-4 Shift Valve: When 1-2 signal fluid pressure exhausts from the 3-4 shift valve (345), the 3-4 shift valve spring (344) moves the valve to the released position. 345 fluid from the 2-3 shift valve flows through the 3-4 shift valve and enters the direct clutch circuit.

Direct Clutch: Direct clutch fluid is routed to the direct clutch piston to apply the direct clutch plates and obtain Fourth gear.

3-4 Shift Accumulation

Direct Clutch Accumulator: Direct clutch fluid is also sent to the direct clutch accumulator assembly. Direct clutch fluid, together with accumulator spring force, moves the direct clutch accumulator piston against accumulator fluid pressure to cushion the apply of the direct clutch.

Coast Clutch Feed

4-5 Shift Solenoid (SS) Valve: The 4-5 SS valve is energized, allowing feed limit fluid to enter the 4-5 signal fluid circuit. 4-5 signal fluid overcomes 4-5 shift valve spring (373) force and moves the 4-5 shift control valve (375) and the 4-5 shift valve (374) to the applied position.

4-5 Shift Valve: In first through third gears, the coast clutch has been fed by 123 fluid. In fourth gear the 4-5 shift valve (374) is applied in preparation for a shift to fifth gear. This causes the coast clutch fluid circuit to be supplied by coast clutch feed fluid, and 123 fluid to exhaust.

Torque Converter Clutch Released

TCC PWM Solenoid Valve: Filtered 2345 or reverse fluid is still available at the TCC PWM solenoid valve. However, depending on the shift pattern, the TCM keeps the pulse width modulated (PWM) solenoid de-energized blocking filtered 2345 or reverse fluid from entering the TCC signal fluid circuit, thereby keeping the torque converter clutch released.

Fluid Pressure Directed in Preparation for a Shift to Fifth Gear

3-4 Shift Valve: 345 fluid is routed through the 3-4 shift valve (345) into the 45 fluid circuit.

#3 Ball Check Valve: 45 fluid seats the #3 ball check valve and passes through orifice #27. This orifice helps to control overdrive clutch apply in fifth gear.

4-5 Shift Valve: 45 fluid is routed to the 4-5 shift valve (374) where it is blocked by the valve in preparation for an upshift to fifth gear.

Overdrive Range, Fourth Gear - Torque Converter Clutch (TCC) Applied