Vacuum Modulator
- Remove hose from vacuum modulator unit. If transmission fluid is evident on vacuum side of modulator or in vacuum hose, replace modulator unit. Fluid indicates that diaphragm is broken.
- Hook vacuum pump to fitting on modulator. Operate pump until gauge shows 18 in. Hg. If gauge reading holds steady, modulator unit is good. If gauge reading drops, diaphragm is bad and must be replaced.
- With modulator removed from transmission, draw 18 in. Hg on vacuum pump attached to vacuum port of unit. Hold finger over end of control rod of modulator unit. When hose is removed, good modulator will push out on control rod due to internal spring pressure.