“converter out” proceeding on to the transmission oil cooler. The TCC is now released.
signal and PCS2 pressure. PCS2 pressure is directed through SV1, SV3, SV2, and again through SV3 to the C4 clutch, applying the clutch. Main pressure continues to flow through SV3, SV2, and the Manual Selector Valve to the C2 clutch, keeping the C2 clutch applied. The TCM supplies current to the PCS2, which controls the rate at which the PCV2 supplies pressure to the C4 clutch, and current to PCS1, which controls the rate at which the PCV1 exhausts the C3 clutch, assuring a smooth transition to sixth range.
• If electrical power is interrupted while the transmission is in sixth range (causing sixth range converter operation [TCC off]) and the Manual Selector Valve is moved to neutral, C2 clutch exhausts through the Manual Selector Valve to exhaust backfill pressure, releasing C2 clutch. The C3 clutch remains applied. With only one clutch applied the transmission shifts to neutral
• The combined application of C2 and C4 clutches produces sixth range operation.
• If electrical power is interrupted while the transmission is in sixth range (causing fifth range converter operation [TCC off]) and the Manual Selector Valve is moved to reverse, C2 clutch exhausts through the Manual Selector Valve to exhaust backfill pressure, releasing C2 clutch. The C3 clutch remains applied. With only one clutch applied, the transmission shifts to neutral.
• PS1 and PS2 remain open (off) providing feedback that SV1 and SV2 remain in the destroked position, and PS3 remains closed (on) providing feedback that SV3 remains in the stroked position. • If electrical power is interrupted while the transmission is in sixth range, PCS1 and PCS2, SS3 and TCC solenoid (if TCC is applied) are de-energized. Although SS3 supplies control main pressure to the top of SV3, control main pressure flows through SV1 to the top of SV3, keeping the valve in the stroked position. Normally open PCS2 exhausts PCS2 signal pressure, allowing the PCV2 to de-stroke, exhausting the C4 clutch. Normally closed PCS1 blocks exhausting of PCS1 signal pressure, allowing PCS1 signal and PCS1 pressure to rise. • PCS1 pressure is directed through SV2 to the C3 clutch, applying the clutch. Main pressure continues to flow through SV3, SV2, and the Manual Selector Valve to the C2 clutch, keeping the C2 clutch applied. The combination of C2 and C3 clutch application produces fifth range operation for limp home capability. • If the TCC is applied, the TCC solenoid deenergizes, causing the TCC valve to de-stroke, exhausting pressure form the top of the Converter Flow Valve. De-stroking the Converter Flow Valve redirects main overage pressure to “converter in” path, then to
Page 42
Copyright © 2005 General Motors Corp.
• If electrical power is interrupted while the transmission is in sixth range, resulting in only fifth range and neutral operation, the engine may be shut down and restarted to attain neutral, drive, and reverse operation. (Refer to paragraph A- Neutral).
I.
Hydraulic Circuit—Reverse (Foldout 11) • When the Manual Selector Valve is moved from neutral to reverse, SS1 de-energizes, turning off PS1. SS2 and SS3 remain energized, keeping PS2 and PS3 on. Reverse signal pressure is exhausted, removing pressure from PS4, turning on the normally closed PS4. • The TCM energizes PCS2 to control the rate at which PCS2 pressure supplies oil to the oncoming C3 clutch, assuring a smooth transition to reverse. As PCS2 is energized, PCS2 signal pressure increases. Initially, the PCV2 gain valve spring keeps the gain valve away from PCV2, so that only PCS2 signal pressure acts on PCV2. As PCS2 signal pressure increases, the PCS2 pressure
1000 and 2000 Product Families Principles of Operation—May 2005
