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Home >> Audi >> 2011 >> A8 L >> Repair and Diagnosis >> Drivelines & Axles >> Driveshaft & Universal Joints >> Rear Final Drive 0BF & 0BE >> 39 Final Drive, Differential >> Disassembly And Assembly >> Hydraulic Control Unit

Hydraulic Control Unit

Fig 1: Hydraulic Control Unit Replacement Components
GWWA39-10370Courtesy of AUDI OF AMERICA, LLC
  1. Bolt
    • 5 Nm
  2. All Wheel Drive (AWD) Pump -V415-
    • Removing and installing, refer to PUMP 
  3. O-ring
    • Always replace if removed
  4. Adapter
    NOTE:

    The adapter could fall out when removing the AWD pump.

    Insert the adapter into the recesses in the hydraulic pump before installing the AWD pump.

  5. Hydraulic Pump
    • Consists of a guide ring, a housing and 6 pistons
    • Assembling, refer to Fig 2
  6. Ball Bearing
    • Can be removed and installed by hand
  7. Left Pipe
    • Tighten the nuts to 30 Nm.
    • Installed between the hydraulic control unit and the left chamber
    • First install the nuts hand-tight
  8. O-ring
    • Always replace if removed
  9. Oil Pressure/Temperature Sensor -G437-
  10. Oil Pressure/Temperature Sensor 2 -G640-
  11. All Wheel Drive (AWD) Clutch Valve 2 -N446-
    • Color: brown
    • Removing and installing, refer to CLUTCH VALVE OR CLUTCH VALVE 2 
    • Installation position: The connector faces upward toward the oil pressure/temperature sensor --
      CAUTION:

      Do not confuse with the AWD clutch valve.

  12. All Wheel Drive (AWD) Clutch Valve -N445-
    • Color: black
    • Removing and installing, refer to CLUTCH VALVE OR CLUTCH VALVE 2 
    • Installation position: The connector faces upward toward the oil pressure/temperature sensor --
      CAUTION:

      Do not confuse with the AWD clutch valve 2.

  13. Bolt
    • 2.5 Nm
  14. O-ring
    • Always replace if removed
    • Position on the clutch valve --
  15. Compression Spring
  16. Guide
  17. Ball
  18. Hydraulic Control Unit Housing
    • With centering pins -arrows-
    • The centering pins hold the hydraulic control unit and seal to the final drive housing.
  19. Ball
  20. O-ring
    • Always replace if removed
  21. Shuttle Valve
    • 8 Nm
    • Removing and installing, refer to Fig 4
  22. Gasket
    • With a screen
    • Mount on the centering pins on the hydraulic control unit housing
  23. Right Pipe
    • Tighten the nuts to 30 Nm.
    • Installed between the hydraulic control unit and the right chamber
    • First install the nuts hand-tight
Fig 2: Assembling Hydraulic Pump
GWWA39-10404Courtesy of AUDI OF AMERICA, LLC

-- Insert the 6 pistons -A- into the housing -B-.

-- Position the guide ring -C- so that the piston touches the collar -arrow-.

-- Install the hydraulic pump -1- and the guide ring -2- into the hydraulic control unit housing.

Fig 3: Hydraulic Control Unit Housing
GWWA39-10447Courtesy of AUDI OF AMERICA, LLC

Functional Check 

-- Turn the hydraulic pump -1- several times. Pay attention to the following when doing this:

Fig 4: Identifying Shuttle Valves, Removal/Installation
GWWA39-10403Courtesy of AUDI OF AMERICA, LLC
NOTE:

Remove the AWD pump, the hydraulic pump and the ball bearing beforehand -item 6-  HYDRAULIC CONTROL UNIT => List Item:Ball Bearing.

-- Remove the shuttle valves -A-. The ball -C- must be removed as well.

-- Insert the ball into the hole in the shuttle valve when installing.

-- Carefully install the shuttle valve with a new O-ring -B- all the way in.

-- Tighten the shuttle valve to the tightening specification -item 21-  HYDRAULIC CONTROL UNIT => List Item:Shuttle Valve.