Modulator Disconnected

With vehicle stationary (service brake on), engine speed set to 1200 RPM, and vacuum modulator tube DISCONNECTED, transmission control pressure should be approximately as shown in Control Pressure Specifications table.

Fig 1: Sectional View of Turbo Hydra-Matic 250C Auto. Trans.

Courtesy of GENERAL MOTORS CORP.

Fig 2: THM 250C Hydraulic Circuits Diagram (Torque Converter Clutch Applied)

Courtesy of GENERAL MOTORS CORP.