Workshop Repair and Service Manuals GMC SIERRA

Reverse Automatic


When the gear selector lever is moved to the Reverse (R)position (from the Park position) the normally high C35R pressurecontrol solenoid 2 is commanded ON and the following changes occurin the transmission’s hydraulic and electricalsystems:

Fluid Pressure Directed in Preparation for a Shift

Manual Valve

With the manual valve in the reverse position, line pressureis directed into the reverse fluid circuit to the #2-ball check valve and clutch select valve-3.

#2 Ball Check Valve

Reverse fluid seats the #2-ball check valveagainst the solenoid-1 fluid passage and fluid is forcedthrough orifice-#22 into the CSV2 enable circuit.

Clutch Select Valve 2

CSV2 enable fluid, present at the valve from Park position,continues to hold the clutch select valve-2 againstclutch select valve-2 spring force.

Low and Reverse Clutch Applies

Clutch Select Valve 3

Reverse fluid from the manual valve is routed to clutchselect valve-3 to combine with clutch selectvalve-3 spring force to keep the valve in the offposition. This allows reverse fluid to pass through the valve andenter the 3-5-clutch reverse feed circuit. The3-5-clutch reverse feed fluid from the clutch selectvalve-3 is also routed to #5-ball checkvalve. CBR1/CBR FD fluid is also directed through the clutch selectvalve-3 to the low and reverse clutch assembly.

Low and Reverse Clutch

CBR and CBR1 fluid pressures are routed to both the inner andouter areas of the low and reverse clutch piston to hold the pistonagainst spring force and hold the low and reverse clutch plates.The clutch was already applied in Park, but is applied with moreholding capacity in Reverse (both piston areas arepressurized).

#5 Ball Check Valve

The 3-5-clutch reverse feed fluid seats#5-ball check valve against the drive 1-6-circuit allowing 3-5-clutch reverse feed fluid to enterthe 3-5-reverse supply circuit. The3-5-reverse supply fluid is then routed to #7 ball checkvalve and through orifice-#25 where it enters the3-5-reverse feed circuit. The 3-5-reversefeed passes through orifice-#46 and then is routed tothe 3-5-reverse clutch regulator valve.

3-5 Reverse Clutch Applies

C35R Pressure Control Solenoid 2

The C35R pressure control solenoid-2 is energized(HIGH) allowing actuator feed limit fluid to enter the PCS3-5-reverse clutch circuit. PCS 3-5- reverseclutch fluid is then routed through orifice- #48 to the3-5-reverse clutch regulator valve and throughorifice-#40 to the 3-5- reverse 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. The 3-5-reverseclutch fluid is then routed to the 3-5-reverse clutchand the 3-5-reverse boost valve. PS1 fluid from pressureswitch-1 exhausts through the valve allowing the switchto close.

3-5 Reverse 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-clutchreverse feed pressure (full line pressure) to the clutch.

3-5 Reverse Clutch

The 3-5-reverse clutch fluid enters the 1-2-3-4and reverse clutch housing to move the piston against spring forceand compensator feed fluid to apply the 3-5-reverseclutch plates.


Reverse Automatic

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