Workshop Repair and Service Manuals GMC SIERRA

Drive Range Third Gear Default Automatic


If the transmission is in 1st, 2nd or 3rd gear during atransmission electrical component failure, the transmission willdefault to 3rd-gear. All solenoids will default to theirnormal state. If the torque converter clutch was applied, it willrelease. This default action will enable the vehicle to be safelydriven to a service center.

1-2-3-4 Clutch Stays Applied

Shift Solenoid 2

Shift solenoid-2 defaults to it'snormally-closed state (OFF), and SOL-2 fluidexhausts through the solenoid.

Clutch Select Valve 3

Solenoid-2 fluid pressure no longer holds theclutch select valve-3 open. When the valve moves back tothe closed position, it opens the 1234-clutch defaultfluid circuit, and 1234-default fluid is routed to the1-2-3-4-clutch regulator valve.

1-2-3-4 Clutch Regulator Valve

With the absence of PCS-1234 clutch fluid, due tothe default state of the C1234-pressure controlsolenoid-5, the 1-2-3-4-regulator valve wouldclose from spring force. However, the 1234-clutchdefault fluid enters behind the 1-2-3-4-regulatorshuttle valve and keeps the valve in the open position.

1-2-3-4 Clutch

With the 1-2-3-4-clutch regulator valve still heldin the open position, the 1-2-3-4-clutch will stayapplied.

3-5 Reverse Clutch Applied or Applies

C35R Pressure Control Solenoid 2

The normal state for the C35R-pressure controlsolenoid-2 is ON, therefore PSC-35 reverseclutch fluid will still be routed to the 3-5-reverseclutch regulator valve and the 3-5-reverse clutch boostvalve.

3-5 Reverse Clutch Regulator Valve

PCS-3-5 reverse clutch fluid moves the3-5-reverse clutch regulator valve against3-5-reverse clutch regulator valve spring force and3-5-reverse clutch feedback fluid. This allows3-5-reverse feed to pass through the valve and enter the3-5-reverse clutch circuit. 3-5-reverseclutch fluid is then routed to the 3-5-reverse clutch,the 3-5-reverse boost valve and the clutch selectvalve-2. When the 3-5-reverse clutchregulator valve is in this position, PS1-fluid from thepressure switch-1 exhausts through the valve, allowingthe switch to close.

3-5 Reverse Clutch Boost Valve

PCS-3-5 reverse clutch fluid pressure acts on adifferential area moving the 3-5-reverse clutch boostvalve against the 3-5-reverse clutch boost valve spring.The 3-5-reverse clutch fluid passes through the valveand enters the 3-5-reverse clutch feedback circuit. AsPCS-3-5 reverse clutch fluid pressure is increased to agiven value, the 3-5-reverse clutch boost valve opensthe 3-5-reverse clutch feedback circuit to exhaust. Thisresults in the 3-5-reverse clutch regulator valve movingto the full feed position sending full 3-5-reverseclutch feed pressure (full line pressure) to the clutch.

3-5 Reverse Clutch

The 3-5-reverse clutch fluid enters the 1-2-3-4and 3-5-reverse clutch housing to move the pistonagainst spring force combined with force from the compensator toapply the 3-5-reverse clutch plates.

Drive Range, Third Gear Default

Drive Range, Third Gear Default Automatic

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