GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 Silhouette 🢒 Brakes 🢒 Antilock Brake System 🢒 Brake Modulator Gear Replacement

Removal Procedure

    Object Number: 183893 Size: MH

    Caution: The modulator drive gears are under spring load and will turn during disassembly. After removing brake modulator drive gear cover, exercise extreme care not to place fingers into the gear set, since fingers can be pinched by rotating gears.

    Notice: Do not allow gear to turn while removing the retaining nut, since the modulator piston can hit the top of the modulator bore, damaging the piston. Place a screwdriver through the holes in the gears (not between the gears) into the recessed hole in the modulator base. This will prevent the gear from turning, aiding in gear removal.

    Important: Do not repair damaged motor packs or brake modulators. Other than modulator drive gears replacement, repair of the motor pack and brake modulator assemblies is not authorized. Do not oil or lubricate the gears on the motor pack.

  1. Remove the ABS modulator/master cylinder assembly. Refer to Brake Modulator/Master Cylinder Assembly Replacement .
  2. Remove the Torx® head screws that attach the gear cover.
  3. Remove the four motor pack to modulator Torx® head screws.
  4. Remove the motor pack from the modulator. Refer to ABS Motor Pack Replacement .

    5. Important: Use care when handling the motor pack. Replace the motor pack if the motor pack is dropped or damaged during handling.


    Object Number: 155167 Size: SH
  1. Remove the gears from the modulator.
  2. Remove three modulator drive gears from the modulator drive shaft retaining nuts.

Installation Procedure

    Object Number: 155167 Size: SH
  1. Position the modulator drive gears onto the modulator drive shaft.

    2. Notice: Do not allow gear to turn while removing the retaining nut, since the modulator piston can hit the top of the modulator bore, damaging the piston. Place a screwdriver through the holes in the gears (not between the gears) into the recessed hole in the modulator base. This will prevent the gear from turning, aiding in gear removal.

    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 three gear retaining nuts.

    3. Tighten
    Tighten the nuts to 8.5 N·m (75 lb in).

  3. With either of the modulators positioned upside down, and the gears facing your, rotate each ABS brake modulator gear counterclockwise until movement stops.

    4. Rotating the modulator gears will cause the following conditions:

    • The pistons on the ABS brake modulator will be positioned very close to the top of the modulator bore.
    • The brake bleeding procedure is simplified.

    Object Number: 183893 Size: MH

    Important: Use care when handling the motor pack. Replace the motor pack if the motor pack is dropped or damaged during handling.

  4. Position the ABS motor pack (1) onto the modulator (6), aligning the three motor pack gears with the modulator gears.
  5. Install four motor pack to modulator Torx® head screws.

    6. Tighten
    Tighten the Torx® head screws to 4.5 N·m (40 lb ft).

  6. Install the gear cover onto the modulator with Torx® head screws.

    7. Tighten
    Tighten the Torx® head screws to 4 N·m (45 lb in).

  7. Install the ABS modulator/master cylinder assembly. Refer to Brake Modulator/Master Cylinder Assembly Replacement .
  8. Bleed the brake system. Refer to Hydraulic Brake System Bleeding in brakes.