G 3500 1 Ton Van V8-454 7.4L (1989)
Vacuum Brake Booster: Description and Operation
Tandem Diaphragm Type
Fig. 6 Exploded View Of Delco-Moraine Tandem Power Brake Unit
Fig. 7 Exploded View Of Delco-Moraine Tandem Diaphragm Power Piston Assembly
These units, Figs. 6 and 7, have a vacuum power chamber that consists of a front and rear shell, a housing divider, front and rear diaphragm and plate
assemblies, an hydraulic pushrod and a diaphragm return spring.
The unit operates in much the same manner as the Single Diaphragm unit described above. The diaphragm and plate assemblies use the pressure
differential created by engine intake manifold vacuum and atmospheric pressure to assist the hydraulic pushrod.