Third Range

Third Range





Third Range Hydraulic Schematic
Before making the shift from second to third range, the Transmission Control Module (TCM) makes certain all of the Shift Valves are in the correct position with the C, D and E Shift Valves up.

B Trim Solenoid is de-energized, exhausting trim signal pressure which allows Trim Valve B to move up, exhausting C4 clutch. Trim Solenoid A is de-energized, raising the A trim signal and A trim pressures. The A trim pressure is directed through Shift Valve D to C3 clutch. The TCM reduces current to Solenoid A, which controls the rate at which Trim Valve A supplies pressure to C3 clutch, and reduces current to Solenoid B. which controls the rate at which Trim Valve B exhausts C4 clutch, assuring a smooth transition to third range. Main pressure continues to flow through the E Shift Valve and Manual Selector Valve to C1 clutch, keeping the clutch applied.

The combination of C1 and C3 clutch application produces third range operation.

After the shift into third range is complete, Solenoid C is energized and directs control main pressure to the top of the C Shift Valve, pushing the valve down. With shift Valve C in its downward position,

C4 clutch feed is exhausted through the C Shift Valve to exhaust backfill keeping the C4 clutch released and C2 clutch has an exhaust path through the C Shift Valve to the B Trim Valve, keeping the C2 clutch released.

Pressure switch C turns on, providing feedback that Shift Valve C is stroked down. Pressure switches D and E remain off, providing feedback that the D and E Shift Valves are in their up position.

If electrical power is interrupted with the transmission in third range, Solenoid C and Solenoid F (If TCC is applied) is de-energized. Shift Valve C will move up, changing the exhaust path of C2 clutch to exhaust backfill and the exhaust path of C4 clutch to the B Trim Valve. Normally closed Trim Solenoid A continues to block the exhaust of the A trim signal pressure (trim signal remains control main). The solenoid signal pressure on top of Trim Valve A produces maximum A Trim pressure, which is routed through Shift Valve D to C3 clutch, keeping the clutch applied. With the Manual Selector in a forward position, main pressure continues to feed C1 clutch through the E Shift valve and Manual Selector Valve. The combination of C1 and C3 clutches applied keeps the transmission in third range for limp home capability. If the TCC is applied, the F Solenoid de-energizes, causing the F Trim valve to move up, exhausting pressure from the top of the Converter Flow Valve. The Converter Flow Valve moves up, redirecting main overage to converter in and converter out to the cooler. The TCC is now released.

If electrical power is interrupted with the transmission in third range, and the Manual Selector Valve is moved to N (Neutral), C1 clutch will exhaust through the Manual Selector Valve to exhaust backfill. C3 clutch remains applied. With only one clutch applied, the transmission goes to N (Neutral)

If electrical power is interrupted with the transmission in third range and the Manual Selector Valve is moved to the R (Reverse) position, C1 exhausts through the manual Selector Valve which releases the clutch. Main pressure goes through Shift Valve E, the Manual Selector Valve and Shift Valve D to C5 clutch. applying the clutch. The combination of C3 and C5 clutch application produces R (Reverse) range for limp home capability.