GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L80-E 🢒 Forward Servo Replacement

Removal Procedure
  1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle .
  2. Remove the oil pan and filter. Refer to Automatic Transmission Fluid and Filter Replacement .
  3. Remove the six forward servo cover bolts, cover, and gasket.

    4. Object Number: 512978 Size: SH
  4. Remove the following parts:
    5. 4.1. Forward servo piston pin (5)
    4.2. O-ring seal (4)
    4.3. Servo piston (3)
    4.4. Retainer (2)
    4.5. Piston spring (1)

Installation Procedure

    Object Number: 512978 Size: SH
  1. Install the following parts:
    2. • Piston spring (1)
    • Retainer (2)
    • Servo piston (3)
    • O-ring seal (4)
    • Forward servo piston pin (5)

    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.

  2. Install the forward servo gasket, cover, and bolts.

    3. Tighten
    Tighten the bolts to 24 N·m (18 lb ft).

  3. Install the oil pan and filter. Refer to Automatic Transmission Fluid and Filter Replacement .
  4. Lower the vehicle.
  5. Fill the transmission to the proper level with DEXRON® VI transmission fluid. Refer to Transmission Fluid Check .

    6. Important: It is recommended that transmission adaptive pressure (TAP) information be reset.

    Resetting the TAP values using a scan tool will erase all learned values in all cells. As a result, The ECM, PCM or TCM will need to relearn TAP values. Transmission performance may be affected as new TAP values are learned.

  6. Reset the TAP values. Refer to Adapt Function .