GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 GMC P62 Commercial Chassis 🢒 Brakes 🢒 Park Brake 🢒 Hydraulic Auto Apply Actuator

Removal Procedure

    CAUTION:: Do not disassemble the actuator. Always service the actuator as a unit. The actuator contains a large spring under tension. Disassembling the actuator allows the spring to expand with great force, which can result in personal injury.

    CAUTION:: If the actuator will not hold pressure, do not unthread the parking brake cable from the actuator piston. The cable is under tension and unthreading the cable will cause the cable to spring and can result in personal injury.


    Object Number: 29081 Size: SH
  1. Block the vehicle's wheels.
  2. If the actuator will not hold pressure, move the column shift lever to the P (Park) position and cut the parking brake cable with a bolt cutter.
  3. If the actuator will hold pressure, turn the ignition ON and move the column shift lever to N (Neutral).

    4. Important: Do not reuse the old fluid.

  4. Position a drain pan to catch the fluid that leaks out.
  5. Remove the access panel on the side of the component box.

    6. Object Number: 29082 Size: SH
  6. Remove the cotter pin.
  7. Remove the clevis pin.
  8. Remove the actuator cable from the fitting.
  9. Remove the cable fitting and the jam nut from the actuator piston rod.

    10. Object Number: 29084 Size: SH
  10. Remove the hydraulic hose and the light switch.
  11. Remove the actuator mounting nuts and the washers.
  12. Remove the actuator.

Installation Procedure

    Important: When replacing any hydraulic components, the hydraulic system should be flushed with Dexron® IIE transmission fluid. This is to ensure that the hydraulic system is free of contaminants such as metal particles that may have been circulated through the system as a result of a component failure.


    Object Number: 29084 Size: SH
  1. Install the actuator.
  2. Install the actuator mounting nuts and the washers.

    3. Tighten
    Tighten the actuator mounting nuts to 108 N·m (80 lb ft).

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  3. Install the hydraulic hose and the light switch.

    4. Tighten
    Tighten the hydraulic pipe fitting to 16 N·m (12 lb ft).


    Object Number: 29082 Size: SH
  4. Install the jam nut and the cable fitting onto the actuator piston rod.
  5. Connect the actuator cable to the fitting.
  6. Install the clevis pin.
  7. Install the cotter pin.

    8. Object Number: 29081 Size: SH
  8. Install the access panel.

    9. Tighten
    Tighten the access panel fasteners to 13 N·m (10 lb ft).

  9. Cycle the system at least six times.
    10. 9.1. With the ignition switch ON, move the shift lever from P (Park) to N (Neutral).
    9.2. Check the fluid level. Refer to Checking and Adding Fluid .
  10. Check the hydraulic system for leaks.
  11. Check the cable. Refer to Hydraulic Hydraulic Auto Apply Actuator Cable Adjustment .