Before making the shift from third to fourth range, the transmission control module (TCM) makes certain all of the shift valves are in the correct position, with shift valve 1 stroked and shift valve 2 and shift valve 3 de-stroked.

Pressure control solenoid 1 (PCS1) is energized, opening the PCS1 signal pressure to exhaust which allows the pressure control valve 1 to de-stroke and the 3rd, 5th, and reverse clutch pressure is exhausted. PCS2 is energized, raising the PCS2 signal and PCS2 pressures. The PCS2 pressure is directed through shift valve 1, shift valve 3, shift valve 2, and the manual selector valve to the 4-5-6 clutch, applying the clutch. Main pressure continues to flow through shift valve 3 and the manual selector valve to the 1-2-3-4 clutch, keeping the 1-2-3-4 clutch applied. The TCM supplies current to PCS2, which controls the rate at which pressure control valve 2 supplies pressure to the 4-5-6 clutch, and current to PCS1, which controls the rate at which pressure control valve 1 exhausts the 3rd, 5th, and reverse clutch, assuring a smooth transition to fourth range.

The combination of the 1-2-3-4 clutch and the 4-5-6 clutch application produces fourth range operation.

After the shift to fourth range is completed, SS3 is energized, directing control main pressure to the top of shift valve 3, stroking the valve. In the stroked position, main pressure is redirected through shift valve 2 and the manual selector valve to the 4-5-6 clutch, keeping the 4-5-6 clutch applied. The flow from pressure control valve 2 to shift valve 3 is directed through the manual selector valve to the 1-2-3-4 clutch, keeping the 1-2-3-4 clutch applied.

Pressure switch 3 turns ON and pressure switch 1 remains ON, providing feedback that the valves are stroked. Pressure switch 2 remains OFF, providing feedback that shift valve 2 is in the de-stroked position.

If electrical power is interrupted while the transmission is in fourth range, PCS1, PCS2, the torque converter clutch (TCC) solenoid, SS1, and SS3 are de-energized. Main pressure continues to flow through shift valve 3 and shift valve 2 and the manual selector valve to the 4-5-6 clutch, keeping the 4-5-6 clutch applied. When de-energized, normally open PCS2 exhausts the PCS2 signal pressure, allowing pressure control valve 2 to de-stroke and the 1-2-3-4 clutch exhausts. After shift valve 1 de-strokes, the 1-2-3-4 clutch exhausts to exhaust backfill. Normally closed PCS1 blocks the exhaust of PCS1 signal pressure, allowing the PCS1 signal and PCS1 pressures to rise. Pressure control valve 1 directs full pressure through shift valve 2 to the 3rd, 5th, and reverse clutch, applying the clutch. The combination of the 4-5-6 clutch and the 3rd, 5th, and reverse clutch applied produces fifth range operation for a limp home capability. If the TCC is applied, de-energizing the TCC solenoid causes the TCC valve to de-stroke, exhausting pressure from the top of the converter flow valve. The converter flow valve de-strokes, redirecting main overage to converter in and converter out to the cooler. The TCC is now released.

If electrical power is interrupted while the transmission is in fourth range (causing fifth range converter operation) and the manual selector valve is moved to Neutral (N), the 4-5-6 clutch exhausts through the manual selector valve to exhaust backfill, releasing the 4-5-6 clutch. The 3rd, 5th, and reverse clutch remains applied. With only one clutch applied, the transmission goes to neutral.

If electrical power is interrupted while the transmission is in fourth range (causing fifth range converter operation) and the manual selector valve is moved to Reverse (R), the 4-5-6 clutch exhausts through the manual selector valve, releasing the clutch. The 3rd, 5th, and reverse clutch remains applied. With only one clutch applied, the transmission goes to neutral.

If electrical power is interrupted with the transmission in fourth range, resulting in only fifth range and neutral operation, the engine may be shut down and restarted to attain neutral, third, and reverse operation.