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Home >> GMC >> 1981 >> Forward Control 4.8L Eng VIN T, Standard Trans >> Repair and Diagnosis (Single Page) >> Brakes >> Mechanical - Hydraulic >> Power Brake Units - DELCO-Moraine Single Diaphragm >> Overhaul >> Power Brake Unit >> Reassembly

Power Brake Unit: Reassembly

  1. Lubricate inside diameter of diaphragm lip with silicon lubricant and fit in diaphragm support.
  2. Install diaphragm and support over power piston and pushrod assembly, support side first. Install new diaphragm retainer and seat using seating tool (J-28458) and a plastic hammer.
  3. Install reaction piston, new reaction disc, reaction retainer and piston rod.
  4. Attach holding fixture to front housing and place in vise. Install power piston return spring with white end to front housing.
  5. Insert power piston assembly pushrod end through rear housing and place on front housing and return spring.
  6. Align scribe marks with spanner on studs of rear housing. Press down and turn clockwise to lock 2 housings.
    NOTE: Assembly can be aided by connecting a vacuum source to booster.
  7. Stake 2 housing tabs into sockets with screwdriver. Stake at 2 tabs 180° apart.
  8. Lubricate inside and outside diameters of grommet and front housing seal and install seal, grommet, vacuum check valve and boot.